US1829649A - Electrical gas analyzing apparatus - Google Patents

Description

Oct. 27, 1931. T HARRISON 1,829,649

ELECTRICAL GAS ANALYZING APPARATUS Filed Nov. 12 935 2 Sheets-Sheet 1 INVENTOR W /"MAM- ATTORNEY Oct. 27,1931. 1', R soN 1,829,649

ELECTRICAL GAS ANALYZING APPARATUS Filed Nov. 12. 1925 2 Sheets-Sheet 2 ATTORNEY Patented Oct. 27, 1931 UNITED STATES PATENT OFFICE THOMAS RANDOLPH HARRISON, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR- TO 4 THE BROWN INSTRUMENT COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A GOR- PORATION OF PENNSYLVANIA ELECTRICAL GAS AN ALYZING- APPARATUS Application filed November 12, 1925. Serial No. 68,650.

The general object of my present invention is to provide improvements in apparatus for determining the composition of a gas by measuring or comparing electrical quantities which are dependent on the thermal conductivity of the gas, which depends in turn upon the composition of gas. Myimproved apparatus is like that heretofore known for the purpose in that it comprises a structure or housing containing cells in each of which is located a resistor, the resistance of which varies with the'temperautre of the resistor, and in that the temperature of each such resistor depends upon the heating efl'ect' of an electric current passing throu h it and upon the cooling effect of a body 6 gas filling the gas cell and conducting heat from the heated resistor to the surrounding wall of the cell. Usually such apparatus comprises at least one cell in which the corresponding resistoris surrounded by the gas to be analyzed and at least one other cell, the resistor in which is surrounded by a standard or comparison gas, whichfre quently is air, so that the composition of the gas to be analyzed is determined by a comparison of the resistance values of. the different resistors which are ordinarily-connected into a Wheatstone bridge.

My present invention comprises improvements in the cell containing structures which facilitate the proper construction of such structures at a relatively low cost of production.

The invention is further characterized by the provisions made for equalizing and regulating the temperatures of the resistors in the construction illustrated the heat dissipating capacity of each resistor may be independently adjusted. The invention in its preferred form is further characterized by the fact that each resistor comprises abody portion in the form of a helix theaxis of which is disposed longitudinally of the elongated cell 'ployed as cell wall materials.

in which the resistor is mounted and in that the terminals of each resistor are mounted in a closure part for one end of the corresponding cell so that the resistor and closure part constitute a resistor unit insertible in the cell through the end of the cell closed by said closure part in the assembled condition of the apparatus. With such a resistor unit the heat dissipating capacity of the resistor can be varied by adjusting one or both of the terminals relative to the closure part in which they are mounted so as to vary the convolution spacingof the resistor.

The invention is further characterized by the fact that the walls of the comparison gas cells, and particularly of the test gas cells, are formed of comparatively non-corrosive material such as lead which is materially more resistant to attack by corrosive furnace gases than are copper and brass which have heretofore ordinarily been em- It has been common practice in the past on account of this corrosive action of the gas to gold plate the interior wall of the brass cell. It has been difiicult to secure a perfect and uniform coating by old lating whereas if the cell walls are 0% lea this difficulty is avoided. In addition to its high resistance to corrosion, lead is advantageous because convenient castings may be used which are less porous than cast brass, and with lead walled cells I avoid diifusion through the cell walls which is sometimes great enough to be objectionable when the cell walls are formed of cast brass. The invention is particularly useful in determining the CO and CO contents of furnace gases, and comprises improved means for obtaining readily comparable measurements and records of the CO and CO2 contents ofthe gases both of which must ordinarily be known to fully determine the character of the combustion conditions producing the furnace gases.

-The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained'by it, reference should be had to the accom an g drawin s and descriptive matter in ii hich I hav illustrated and described preferredembodiments of the invention.

Of the drawings:

ig. 1 is a diagrammatic representation of apparatus for measuring the CO and CO content of the flue gases; v

Fig. 2 is a plan view of one of the comparison cell structures employed in Fig. 1, with the top cover broken away;

Fig. 3 is an elevation partly broken away ind 1n sectionon the broken line'33 ofig. 2; F Fig. 4 is a section on the line 4- 1 of ig. 2; y .B Fig. 5 is a section on the line 55 of Fig. 6 is a transverse section of piping employed in Fig. 1;

Fig. 7 is a diagram of circuit connections which ma be .employed with the apparatusshown in ig. 1; and

Figs. 8 and 9 are diagrammatic representations of two different arran ements for continuously supplying a stanfardor comparison gas to a comparison cell structure.

The apparatus shown diagrammatically in .Fig. 1, comprises a sampling tube A adapted tobe inserted into the furnace chamber or flue from which furnace gases are to be with- I drawn for anal sis. The gases thus with- .drawn from t e sampling tube A pass through a pipe 'B to-the inlet of a condenser C for eliminating moisture from the gases. From the condenser, the. gases pass through a pipe B to a filter D for eliminating furnace dust" from the gases- The gasoutlet pipe B from 'the filter D, has two branches B and B. The branch B leads to the gas inlet of a device. E containing comparison cells for determining the CO content of the gases. The gases entering the device E pass from the latter through a pipe B to a device EA containing comparison cells for determining the CO content of the gases withdrawn through the sampling tube A. The filter outlet pipe branch B leads to the inlet of a furnace F containing copper oxide or the like oxidizing agent for converting the CO content of the gases entering the furnace into C0 The gasthus modified passes from the furnace F through pipe B to the device EA. The gases entering the device EA through the pipes B and B, are withdrawn from the device "EA through a ipe B running to the inlet of an aspirator (gin which water supplied under pressure through the pipe L creates the draft for causing the above described flow throughthe apparatus. G represents the outlet from the aspirator through which the air, gas, and aspirating'water aredischarged.

As shown, the aspirating water is supplied from a pipe L and is ut lized incooling the condenser C, the gases passing through the pipe B and B and the devices E and EA. For this purpose the supply pipe L is connected to the water inlet of the condenser C,

denser B, filter D,'or oxidizing furnace F,

but, on the contrary, theseelements of the apparatus shown in F ig. .1, may well be of the known type. The device E in the preferred construction illustrated. in Figs. 2, 3, 4, and 5 comprises a cup shaped body member which may be made ofcast iron or other suitable metal, and is formed with a water jacket space E? surroundin its main cavity EC. The cooling water supp y pipe L is connected to the bottom of the space E and the cooling water outlet pipe L is connected to the to? of that space. As shown, the body member is formed with two Vertical channels E and E*,-the gas supply pipe B being connected to the lower end of. the channel E At its upper end the body of the device E is provided with a seat E surrounding the cavity E. and against which is secured the flanged head of a member e, as by means of stud bolts, E", a gasket being advantageously interposed between the member 6 and seat E to prevent gas leakage.

The member 6 is provided with a depend- .ing portion 6 which terminates a short distance above the bottom wall of the cavity E, and conforms more or less closely in cross sectional outline to the cavityE but is smaller than the latter-to provide a temperature ,equalizin gas space between the outer surface ofthe portion 6 and the surrounding wall of the cavity E. The member 6 may well be cast ofa suitable" metal as brass or lead, and is formed with acavity' which is open at its lowerend and extends from the bottom of the portion-e up into the flanged head of the membenand is filled by a lead core e The comparison resistance containing cells 6 and e are formed-inthe lead core e As shown, there are two cells e which re- .ceive gas at their upper ends from the'channel' E through channels 6 and e formed in the brass portion of the member 6. The cells directly into the top of the equalizing space through a port 6 The cells e, of which there are two-in the construction illustrated, differ from the cells e in having closed lower ends. Each cell 0 communicates through a corresponding channel c with a drying chamber a, formed in the lead core c and containing calcium chloride or the like.

The upper end of each of the cells e and e is in register with a corresponding hole formed in the head of the member 6, and

shaped to provide a seat for a plug M closing the upper end of'the cell and for threaded engagement with a gland M securing the plug M in place. The plugs M closing the upper ends of the cells 6 and e may be all alike and are formed of'insulating material. As shown, each plug M is formed with a central passage for a resistance terminal 0 in the form of a bar which extends through the plug, and may be secured in any desired axial adjustment therein by means of a set screw 0. The terminal bar 0 in each cell 6 has its lower end secured-- to the upper end of a corresponding resistance Re which is in the form of a helix and has its lower end connected to a terminal P shown as a metal rod secured in a passage formed for the purpose in the corresponding plug M. As shown, the lower end of each terminal P carries a spider P of insulating material for centering the lower end of the resistance in the corresponding cell without closing the latter. The terminal bars 0 extending into the upper ends a of the cells e, have their lower ends connected to the upper ends of helical resistances Re which have their lower ends supported by arms P and spiders P just as do the resistances Re The upper end of the drying chamber 6 is closed by a plug m threaded into an opening formed in the head portion of the member 6.

In the preferred construction illustrated, a so-called Wheatstone bridge balancin resistance in the form of a slide Wire is mounted on the periphery of a semi-cylindrical block of bakelite or other insulatin material S secured to the head of the mem er 6. The block S has journalled in it a shaft S carrying a brush S which bears against the resistance S at a point depending on the angular position of the shaft S The latter,

as shown, is provided with a kerf in one end to permit of its engagement and rotation by a screw driver or key which may be inserted through an opening E normall closed by a screw plug, which is provided for the purpose in a metallic hood or cover E detach-- ably mounted on the flanged head of the member E. In the construction shown, there is also secured to the top of the member 6 beneath the hood E, a block Q of bakelite or other suitable insulating material which carries binding posts 9 through which the I'BSIS, tors R63 and R6 are connected to the terminal then mounted in said holes.

leads or conductors of the, device E which, as shown, are incorporated in a cable Q, advantageously entering the space under the hood E through a vertical channel E formed in the. housin body.

The device EA may be identical in construction with the device E-except that in the device EA the drying chamber 6 and the channel e are not required and may be omitted, and in that the cells e of the device EA are connected at their lower ends by ports e with the space beneath the member e, and are. connected at their upper ends by channels e and e to the channel E in the body of the device E. In the device EA the channel E is not closed as in the case of the device E. Instead the upper end of the channel E in device EA is open and a passage similar to passage 6 connects the passage E with the gas receiving chambers e, which in device E were used to contain the standard gas. The channel E of the device EA is connected at its lower end to the pipe B, and the gas with its original CO content converted into CO in the furnace F, is thus passed through the cells e of the device EA, and is Withdrawn from the latter through the pipe L along with the portion of furnace gases coming to the device EA from the device E through the pipe B which is connected to the lower end of the channel E and thereby g) the upper ends of the cells- 0 of the device The channel E is not required in the device E and may be omitted. In general, however, it is desirable from a manufacturing standpoint, to have the devices E and EA as nearly alike as is possible, and the cast metal portions other than the lead core parts of the devices E and EA may, therefore, well be identical in form. An advantage of the cell containing structures illustrated is that they require a minimum of machining for their ordinarily are drilled. After this the lead forming the core e is poured into the portion e, suitable cell forming pattern cores being The channels or ports 6 e", e and e or 6 and e, are then drilled. As shown, the channels 6 are formed by drills extending into the cells 6 through the upper ends of the latter. The outer ends of the channels e and 8 are closed by screw plugs e.

To preliminarily cool the gases passing to the comparison cell devices E and EA, a porclose contact as the pipes B, B, andL are shown in Fig. 6, and brazed together.

In Fig. 7 I have illustrated diagrammatically, one form of circuit arrangements by which the resistances Re and Re of the de-v Vices E and EA may advantageously be employed in connection with a single meter K to exhibit in a readily comparable manner the CO, and CO contents of the gases drawn into the apparatus through the sampling tube A. In Fig. 7, the two resistances R63 of the device E form opposing arms of a Wheatstone bridge, of which the other two arms are formed b the resistances R0 The bridge is energize by a source of current as a battery U, conductors 1 and 2 connecting the battery to opposing junction points of the bridge. As shown, the conductor 2 is connected to the slide wire brush S which forms one junction of the brid e, the slide wire resistance S connecting adjacent ends of one resistance Re and one resistance Re. U represents an ammeter for measuring the bridge energizing current, and U an adjustable resistance in the conductor 2by which the strength of thebridge current can be regulated. ,The other two junction points of the bridge of the device E are connected by conductors 3 and 4 to terminals of a switch I.

The resistors R63 and R6 of device EA are connected into a Wheatstone bridge arranged, energized, and connected to terminals of the switch I as is the-bridge of the device E. The connections to the bridge of thedevice EA comprise conductors 10, 20, 30,

and 40 corresponding to the conductor 1, 2, 3,

- and 4:, respectlvely, associated with the bridge of the device E. The switch I is intended for manual or automatic actuation to separately connect the two bridges in regular alternation to the winding of an indicating or recording galvanometer K. Advantageousl'y, though not necessarily, the pointer K of the meter K swings over the meter scale K in one direction from the zero point K of the scale when connected by conductors 3 and 4 to the bridge E to thereby indicate the CO content of the gas, and swings in the opposite direction from the zero point to indicate the 00 content of the gas when the meteris connected through conductors 30 and 40 to the bridge of the device EA.

With the meter pointer thus swinging in opposite directions from the zero point of the instrument to indicate CO2 and CO contents,

respectively, the zero point is preferably located at one side of the center of the scale so that the instrument w1ll give a. wider range of scale readings when measuring CO than when measuring G0, which is desirable in view of the fact that the CO variations will normally require a wider range of movement of the-pointer for their proper indication than will the CO measurements. With the arrangement for this purpose shown in'Fig. 7 the portion of the scale K at the rightof the zero point K will ordinarily be graduated in CO percentage units, while the portion of the scale at the left of the zero point I v will be graduated in CO percentage units. When, as will be usually the case, the meter K is a recording meter, the location of the CO and CO records at opposite sides of the zero line makes it unnecessaryto have the two records made in different colors, though of course, they may be colored differently, but records in two colors, will ordinarilybe desirable, though not essential, if the instrument is arranged to have its pointer swing T'in the same direction from zero in making the CO and CO records. Except as it may pared with the air in the cells e will cause the resistors. Re to be hotter and in consequence to have higher resistances than the reslstors Re by an amount which is dependent on the amount of CO in the gases passing 'through the cells 6 Similarly when the bridge of the device EA is connected to the winding ofthe meter K, the instrument pointer K will be deflected more or less'according to the excess inthe CO content of the gases passing through the cells e over the CO of the gases passing through the cells a the CO n the gases passing through the cells e having about the same thermal conductivity as air and other constituents, aside from CO of ordinary furnace gases. It will be understood that in the Wheatstone bridges shown in Fig. 7, the same general operation would follow if one resistance Re and one resistance ing structure illustrated, is the ready feasibility of incorporating more than one pair of comparison'cells in a singlemetallic block or body, since each cell blockcan be made large enough to incorporate as many cells as may be required and the different resistors are in sulated from the cell block.

In practice, the electrical determination of gas composition, based on the thermal conductivity of the gas, requires a comparison of effects due to the different thermal conductivities of the test gas and of a standard gas as the electrical quantities measured differ so slightly as to make absolute measurements based on the test gas alone, uncertain and unreliable. In comparing a test gas with a standard gas, the latter instead of being sealed in the cells 2 of such a device as the device E described above, may be passed at a suitable rate through the cells 6 of a device like the device EA. One arrangement by which a' proper flowof a standard gas through the cells 6 of a device EA may be maintained is illustrated in Fig. 8, wherein the cells 0 are supplied with the test gas through the pipe B as in the arrangement shown in Fig. 1, while a standard gas is supplied to the cells 6 from a source of gas under pressure of gas as a tank W. To maintain a constant rate of flow through the pipe W into the cells 6 the pipe W is shown as provided with a pressure reducing valve W and with a measuring orifice IV between the valve W and the cells a. In Fig. 8, W represents a valved filling connection for the tank IV, and W an outlet through which gas may be withdrawn from time to time for analysis by chemical or other suitable methods. Fig. 9 illustrates another form of ap paratus for obtaining the same general result. The apparatus shown in Fig. 9 differs from that in Fig. 8, in that the tank W is employed as a flow equalizing reservoir which is interposed between the pipe W and the outlet pipe X of an air or gas pump X drawing the standard gas from the atmosphere or other source of supply through the pump inlet X The arrangement shown in Fig. 9, makes it unnecessary to employ the measuring orifice IV and reducing valve W and particularly the latter, of Fig. 8. Vith arrangements of the character shown in Fig. 8 and Fig. 9, the

standard gas may be air or may be any other suitable and available gas. and in particular may be whatever available gas is best adapted for comparative purposes to the character of the particular gas being analyzed.

The apparatus disclosed possesses numerous important practical advantages. The accuracy of comparison cell measurements depends, of course, upon the elimination of all temperature differences between the cells.

compared except the difference which results from the different thermal conductivities of the gases in the cells. The provisions made herein for cooling the gases and equalizing temperature conditions in the devices E and EA. tend to eliminate temperature differences other than those upon which the operation of the apparatus depends. The flow of water through the water jacket space E of each of the devices E and EA tends, of course, to equalize the temperatures in the cell structure as a whole, and in conjunction with the preliminary cooling of the gas by heat transfer between the pipe B and the pipe L in the case of the deviceE, and by heat transfer between the pipes B B and L in the case of the device EA, tends to bring about a desirable equality in temperature of the gases entering the comparison cells and the metal walls of the cells. In addition to the temperature equalizing effect of the water cooling provisions, the reduction in gas temperature produced by those provisions is of itself a desirable matter as it tends to reduce the moisture content of the gases and thereby to eliminate the errors which variations in the moisture content of the gases produce.

The mechanical structure of the devices E and EA is obviously simple and desirable for reasons already explained. Furthermore,

the fact that the gas cells are formed in a cell block separable from the body of each'comparison cell structure, makes it possible to do rough mounting work including the attachment of all pipe connections to each such body before the corresponding cell block is ut into place, and thus eliminates a source 0 injury by mechanical shock to the resistance filaments which are relatively delicate and easy to injure.

'lVith the described construction, the resistors Re or Re which are helical in form, are each connected at its opposite ends to rigid conductors O and P both mounted in the same insulation-plug M. The axial adjustment of each of the terminal conductors O in its supporting plug M is an important characteristic of the apparatus since such adjustment permits of a variation of the tempera ture and thereby the resistance attained by the resistor under any given conditions of operation. This follows from the fact that the rate at which the resistor dissipates heat is increased, other things being equal, by spreading the resistor convolutions farther apart, and is diminished by bringing them closer together. This feature of the invention makes it readily possible to'accurately calibrate the apparatus by first makin the various resistors of the proper lengt s to have equal resistances when carrying currents too small to produce appreciable heating. and then. after. the cold resistances of the resistors are thus equalized, spacing the convolutions of the different resistors to equalize their resistances when the resistors are heated by a current large enough to produce an appreciable heating effect and, are exposed to the same cooling conditions.

The resistor arrangement disclosed offers an easy method of obtaining a condition which has heretofore been impracticable to be adjusted while the apparatus is in, or 111 condition for operation, the necessary adj ustmentmay readily be made with each individual instrument, which is evidently impossible if different sizes of resistor wires are used for resistors Re and R6 or if different diameters are used for cells 6 and e as have heretofore been suggested. The method just described is superior also to the method of balancing the bridge when using unlike gases in cells a and e .by adjustment of the slide Wire S, because when the slide wire is placed in a position other than that which balances the bridge when the resistors are unheated, the meter reading will change when the bridge current varies slightly when normal gas is in cells 0. When balanced with normal gas no error is produced at this reading by the galvanometer temperature coeflicient.

. The disclosed mode of mounting the'resistors in the cell blocks avoids all necessity for grounding the resistors to the cell block, and

thus permits of the use of two resistors Re and two resistors Re mounted in a. single cell block and connected in a single Wheatstone bridge as shown in Fig. 7 which is not possible when one end of each resistor is grounded by contact with the cell block, as has heretofore been the usual practice. The formation of the cells in a lead body is advantageous not only from the standpoint of simplicity and cheapness of the mechanical construction, but also because lead is not subject to injurious attack by sulphur compounds or other constituents of furnace gases which have a corrosive action on such metals as iron, cops per, and brass. Lead, moreover, is sufficiently nonporous to prevent the pollution of the standard gas in the cells 6 of the device E,

for example, by the gas passing througlvthe cells 0 as a result of gas diffusion through the pores of the cell wall, as would occur with a cast iron or brass cell block. The corrosion of the cell walls, if not otherwise objectionable, is to be avoided because it tends to vary the rate of heat transfer between the cell wall and the enclosed resistor. f

Some indication of the importance of the desirable properties possessed by lead, in a material forming the walls of gas cells is afforded by the fact that it is now common commercial practice to form gas cells in a brass body and then to coat the cell walls with locked with the cellcontaining lead body by casting the lead into recesses in, or about projections from the piece of stronger metal.- T his interlocking of the strong metal cell mouth piece and cell containing body can be obtained, of course, with strong metal parts very different in shape from the parts 6 shown in the drawings. For example, the part 6 may be replaced by a simple ring or collar cell mouth part imbedded in .the lead cell containing body, by casting the latter about such mouth piece and a cell forming core part mounted in the mouth piece.

Certain novel features of the invention dis closed, but not claimed herein, are claimed in my copending application Serial No. 130,216, filed August 19, 1926, resulting in Patent Serial No. 1,818,619, granted August 11, 1931, which in certain respects is to be regarded as a continuation of thepresent application.

lVhile in accordance with the provisions of the statutes, Ihave illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled'in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims and that in some cases certain features of my invention maybe used to advantage without a corresponding use of other features.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

-1. A'cell block for use in measuring the thermal conductivity of a gas comprising a body of lead with a gas cell therein and a support for said body made of metal which is stronger than lead and formed with a hole in register withone end of said cell, and a resistor support mounted in said hole.

2. A cell block for use in apparatus for communicating at one end with said hole.

3. A cell block for use in apparatus for measuring the thermal conductivity of a gas comprising a body of lead, a member made of a metal stronger than lead and formed measuring the thermal conducivity of a gas comprising a body oflead, a member made closed end of said chamber and having a gasreceiving cell formed in said lead body and communicating at one end with said hole, and a resistor support mounted in said hole and closing the corresponding end of said cell.

4. A cell block for use in apparatus for measuring the thermal conductivity of a gas comprising a body of lead, a'member made of a metal stronger than lead and formed with a chamber open at one end and closed at the other in which said lead body is held and" having a hole extending through the closed end of said chamber, and having a gas receiving cell formed in said lead body and communicating at one end with said hole, and a gas passage communicating with said cell and formed partly in said lead body and partly in said member.

5. Apparatus formeasuring the thermal conductivity of a gas comprising a metallic body member formed with a chamber open at one end and closed at the other and a cell block formed with a gas cell and extending into said chamber through the openend thereof and separated from the surrounding wall thereof by a gas receiving temperature equalizing space.

6. A cell structure for use in determining the thermal conductivity of a gas comprising a metallic body member formed with a chamber, a Water jacket space surrounding said chamber, and a cell block removably received in said chamber and separated from the surrounding wall thereof by agas receiving temperature equalizing space.

- passin 7. In apparatus for measuring the thermal conductivity of a gas, a body part formed with a cell block cavity, a water jacket space surrounding said cavity, and a gas channel, pipe connections to said body part for passingswater through said jacket space and for gas through said channel, and a cell block Tormed with a gas cell and a channel communicating with said cell and adapted to be detachably secured to said body part with the portion of the block containing said cell received in said cavity and with the channel in said cell block in communication with the channel in said body part.

8. In apparatus for measuring the thermal conductivity of a gas, a cell block formed with a cell open at one end, a body of insulation mounted in the open end of the cell,

terminal conductors carried by said body and extending into said cell, and a resistor located in said cell and having one end connected to one of said terminal conductors adjacent one end of'the cell and having its opposite end connected to the other terminal conductivity of a gas, a cell block formed with-a cell open at one end, a body of insulation mounted in the open end of'the cell, terminal conductors carried by said body and extending into said cell, and a resistor located in said cell and having one end connected to one of said terminal conductors adjacent one end ofthe cell and having its opposite end connected to the other terminal conductor adj acent the opposite end of the cell, one of said conductors being adjustable in said body in the direction of the length of the cell.

10. In gas analysis apparatus, a cell block formed with a cell open at one end, a body of insulation mounted in the open-end otthe cell, terminal conductors carried by said body and extending into said cell and a helical resistor located in'said cell and having one end connected to one of said terminal conductors adjacent one end of the cell and having its opposite end connected to the other terminal conductor adjacent the opposite end of the cell, and means for relatively adjusting said terminal conductors axially of the ce Y 11. In apparatus for measuring the thermal conductivity of a gas, a body part formed with a cell block cavity and with a gas chan nel, and a cell block formed with a. gas cell and with a channel communicating with said cell, and adapted to be detachably secured to said body part with the portion of the block containing said cell received in said cavity and with the channel in said cell block in communication withthe. channel in said body part.

12. A cell block for use in measuring the thermal conductivity of a gas comprising a body of lead having a gas cell formedjherein, and a piece of metal which is stronger than lead and which is formed with a hole constituting an extension of said cell at one end of the latter, and which is imbedded in said lead body.

13. A resistor unit comprising a supporting part adapted to form a closure for one 'end of a cell chamber of gas analysis apparatus, a helical resistor adapted to be inserted in said cell chamber, and means including a terminal of said resistor connecting the latter to said supporting part and adjustable to vary the convolution spacing of said resistor.

. 14:. In gas analysis apparatus comprising :1 cell chamber open at one end and a resistor unit insertible in said cell chamber through the open end thereof comprising a resistor supporting part forming a removable closure for said open cell chamber end, a helical resistor, and means connecting said resistor to said part andadjustable to vary the spacing of the convolution of said resistor.

15. In gas analysis apparatus comprising a cell chamber open at one end and a resistor unit insertible in each cell chamber through the open end thereof comprising a body adapted to be mounted in and close said open chamber end, "and a helical resistor having terminals passing through said body, said body and terminals beingrelatively adjustable to vary the spacing of the resistor convolutions.

16. In as analysis apparatus comprising a cell cham er, a resistor located in said cell chamber, and adjustable means for varying the heat dissipating capacity of'the resistor.

17. In gas analysis apparatus comprising a cell chamber, a resistor located in said cell chamber, and means including a part extending through the cell chamber wall for prising a cell structure formed with a cell chamber, a resistor mounted in said chamher, and means for relatively adjusting said structure and resistor to vary the rate of heat transfer between the resistor and the structure.

20. In apparatus for gas analysis comprising a cell chamber, a helical resistor within said chamber, and supporting means for said resistor adjustable to vary the convolution spacing ofsaid resistor.

21. In gas analysis apparatus comprising a test gas cell, a comparison cell, a resistor in each cell, and means for adjusting the heat dissipating capacity of one of said resistors.

22. In gas analysis apparatus comprising a test gas cell, a comparison gas cell, a helical'resistor in each cell, the two resistors having the same resistance value when cold, andmeans for adjusting the convolution spacing of one of said resistors to regulate the relative resistance values of the two resistors when heated. V r 23. A device for-use in determining the thermal conductivity of a gas comprismg a metallic body member formed with a chamber, a cell block received in said chamber and separated from the surrounding wall thereof by a gas receiving, temperature equalizing space and formed with a cell communicating 'at one of its ends with said space, means for withdrawing gas from said space, and means for separately supplying gas to said space and to said cell at its-second end.-

24. Gas analysis apparatus comprising in combination a cell structure including a standard gas cell, a test gas cell, a resistor'in each cell spaced from the walls thereof and arranged for heat dissipation therefrom through the gas and cell structure, an elec trical indicating instrument and an energiz-- ing and balancing circuit into which said reslstors and instrument are connected, said resistorshaving such resistances when cold,

ductivity which'is diflere nt from that of th standard gas. 1

25. A cell structure for use in determining thethermal conductivity of a gas comprising a metallic body member formed with a chamber and a cell block, received in said chamber and separated from the chamber wall thereof by a gas receiving, temperature equalizing space.

26.'A' gas analysis apparatus comprising thermal conductivity cells for the reference gas and for the analysis gas, resistance heating elements in each cell, and meansassociated with the heating elements of the respective cells for equalizing the heat dissipa-' tion of the cells.

27. In apparatus for analysis of fluids by thermal conductivity having a unit comprising a-body provided with a chamber to receive fluid and a heating element in said chamber, said unit being constructed and arranged for substantial dissipation of heat from said heater through said fluid and body,

and means operating on said unit for adjusting the relative positions of parts of said unit to thereby vary the heat dissipation from the element.

28. In apparatus for analysis of fluids by thermal conductivity having a unit comprising a body provided with a chamber to receive fluid and a heating element in said chamber, said unit being constructed and arranged for substantial dissipation of heat from the element through the fluid and body, and means available exteriorly of and operating on theunit for adjustment for adjusting the relative positions of parts of said unit to any the heat dissipating capacity of said um 29. In apparatus for analysis of fluids by thermal conductivity having a 'unit comprising a body provided with a chamber to receive fluid and a heating element in said chamber, said unit being constructed and arranged for substantialv dissipation of heat from the element through the fluid and body,

and mechanical means available exteriorly of the unit operable to vary the spatial rela tion of the heating element and the fluid in heat transfer relation therewith for varying the rate of heat dissipation from said element.

30. In apparatus for analysis of fluids by thermal conductivity havinga unit comprising a body provided with a chamber to receive fluid and a heating element in said chamber,

said unit being constructed and arranged for substantial dissipation of heat from the element through the fluid and body, and means operable to vary the spatial relation-of the heating element and the fluid in heat transfer relation therewith for varying the rate of heat dissipation from said element.

31, In apparatus for analysis of fluids by thermal conductivity having a body provided with a chamber to receive fluid, a heating element arranged in said chamber for substantial heat dissipation through the fluid and body, and means for adjusting the area of contact effective for heat transfer between the fluid and the element and chamber walls.

32. In apparatus for analysis of fluids by thermal conductivity having a body provided with a fluid receiving chamber open at one end, a unit insertable into said chamber through said open end, said unit comprising a closure for the open end and a heating element carried by said closure, and means operable to vary the spatial relation of the heating element and the gas in heat transfer relation therewith for varying the rate of heat dissipation'from said element.

33. In apparatus for analysis of fluids by thermal conductivity having a test cell and a standard cell, each cell being provided with a fluid receiving chamber, a heating resistor ,in each cell arranged for substantial heat dissipation through the fluid, a Wheatstone bridge'containing said resistors, means for balancing said bridge when the heating resistors, fluids and cells are in a steady tem-' perature state, and means operating to modify the heat dissi ation of at least one system comprising ce 1, resistor, and fluid,

adjustable to balance said bridge at a different steady temperature state.

34. In a gas analysis apparatus having a cell structure including a standard gas cell, a test gas cell, a resistor for each cell arranged for dissipation of heat through gas within the cell by thermal conductivity, a Wheatstone'bridge containing said resistors, electrical means for balancing the bridge when the resistors are cold, and means for adjusting the capacity of the system, comprising the cell structure and gas and resistors contained therein,for dissipating heat from the resistors so as to balance the bridge when the resistors are at operating temperatures and the test gas cell contains gas of predetermined composition and the standard gas cell contains a standard gas.

35. Apparatus for the analysis of gas havcell, a resistor in each cell, a Wheatstone bridge containing said resistors, each cell together with the resistor and fluid contained therein forming a unit, means for adjusting through said sampling device, conditioning device and cell, a comparison gas in the other cell, a resistor in each cell, a Wheatstone brid e containing said resistors, said resistors eing above room temperature in normal operation, and adjustable means operable to vary the spatial relation of at least one resistor and the gas in heat transfer relation therewith for varying the rate of heat dissipation from said resistor.

37 A thermal gas analysis structure comprising a cell body formed with an elongated gas receiving cell chamber, an elongated resistor in said chamber extending longitudinally of the chamber and separated from the surrounding wall of the latter by a gas space, and means including an operable part extending through the chamber wall for varying the cross sectional area of the portion of said gas space through. which heat may pass in a direction transverse to the length of the chamber from said resistor to the surrounding chamber wall. 7,

38. A thermal gas analysis structure comprising a cell body formed with an elongated gas receiving cell chamber, a resistor in said chamber in the form of an elongated helix extendin longitudinally ofthe chamber and separated from the surrounding wallof the latter by a gas space, and means including an operable part extending through the chamber wall for varying the cross sectional area of the portion of said gas space through .Signed at Philadelphia, in the county of Philadelphia, and State of Pennsylvania,

this 10th day of November A. D. 1925.

THOMAS RANDOLPH HARRISON.

ing'a pair of cells, a gas sampling device, a

gas conditioning device, pipe connections to convey gas from the sampling device to the conditioning device, pi e connections to convey gas from the con itioning device to a cell, a gas pump for causing gas to flow through said sampling device, conditioning device and cell, a comparison gas in the other

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