June I, 1882] 



NATURE 



115 



the substance could be heated in a test-tube ; and the other con- 

 sisted of a platinum vessel to constructed that the substance 

 cuulJ lie inserted into a horizontal tube. 



Although Laspeyres in the article just quoted argues most 

 conclusively that an absolutely constant temperature cannot be 

 maintained by controlling the gas-supply, and Jac Myers con- 

 cludes his considerations on the subject by saying, " For so long 

 must we give up the hope of being able to regulate these tem- 

 peratures at pleasure," yet the subject of temperature-regulators 

 is one to which so many have at various times turned their 

 attention, that a comparison of the different methods is not 

 without interest. Most of the instruments constructed maybe 

 classified under one or another of the following heads, viz., as 

 modified : — 



Air thermometers, with mercury or other fluid arranged to 

 control supply of gas : — (a) in which the mercury employed 

 becomes more or less heated while in use ; [6] in which the 

 mercury or other fluid does not tecome heated. 



Mercurial thermometers (<i) acting directly on gas-supply ; 

 (/>) acting on gas-supply through the intervention of electric 

 arrangements. 



Vapour-tension thermometers. 



Air \Thermometers (a). — Kemp's regulator (1852) consists of 

 a glass tube, at one end of which an elongated bulb is blown : 

 the part of the tube near the bulb is then bent so that the open 

 end of the tube and the bulb are parallel. 1 Sufficient mercury is 

 then introduced to partly fill the 1 ulb, the remaiidcr being 

 occupied by air. To the open end of the tube is cemented a 

 brass cap, which is provided at the side with the ga- inlet tube, 

 and in the centre w ith a stuffing box, through which the bra-s 

 outlet tube slides. The temperature is adjusted by moving this 

 tube up or down as the case may be. 



Bunsen's modification made the apparatus more compact, but 

 not so simple or easy of construction.- It consists of a glass 

 cylinder whose lower part is closed, and serves as air-ves-el 

 which communicatee with the upper portion by a tube reaching 

 nearly to the bottom. In the upper portion is inserted a wide 

 glass tube which is provided with a side-tube, and which dips 

 into the mercury. Fastened to the upj er end cf this tube is the 

 gas-supply tube, which is rather shorter, and w hich has a fine 

 opening in it. The position of these tubes is adjusted by the 

 screw-thread in a brass cap, which works on a corresponding 

 thread in the supply tube. The two parts of the apparatus are 

 held together by a spring (in the newer patterns this is replaced 

 by a pin working in a groove). 



His low-temperature regulator has a much larger air-chamber, 

 so as to increase its sensitiveness. 3 It is also provided with a 

 side-tube fitted with a stopcock, so that mercury may be added 

 or drawn off at pleasure. Guthrie 4 (1868) constructed a regu- 

 lator on Kemp's principle, but attached the top of the vertical 

 tube to the bottom of an U-tube which the gas had to traverse, 

 so that the mercury on rising checked the flow . The adjustment 

 consisted of a side tube (bent at a right angle) attached to the 

 vertical tube ; in that tube a glass red could be raised or de- 

 pre-sed, being held in its pi sition by passing through a perforated 

 cork. Muncke's 5 (1876) is very similar to Bunsen's, but the 

 bras; cap and fittings are entirely dispensed with, as the gas- 

 supply pipe works stiffly through a perforated cork which fits the 

 top of the tube 



Air Thermometers (/>). — Schorer 6 (1870) u.-ed for an air-vessel 

 a test tube 60mm. X 14mm., fitted with an india-rubber cork, 

 and connected by a narrow tube with one limb of an U-tube, partly 

 filled with mercury, the other limb being fitted with the control 

 arrangement of Bunsen's 1 attern. 



Clowes' (187 1) constructed an apparatus on the same 

 principle, but added a small ouilet tube at the bottom of the U- 

 tnbe, so that by means of an india-rubber tube, which is closed 

 by a screw clip, the mercury level in the U-tube may be ad- 

 justed. In his apparatus the gas exit consisted of a glass tube 

 passing through a perforated cork. 



Jeannel* (1872) used a metallic air-vessel of 300-400C.C. 

 capacity, communicating, as in Schorer's, w ith an U-tube (charged, 

 however, with glycerine instead of mercury). The pressure of 

 the air in the vessel is regulated by means of an india-rubber 

 ball, which is fitted (by means of a T-piece and stopcock) to the 

 > William: 



" Chem. Manip. ," 49. 



' Price List,'* Fig. 614. 

 1 PJULMag. xmvi. 30(1868); Strecker's 

 5 I'ing. Polyt. Journ. 219, 72 (1876). 

 « Fres.Zeit. Anal. Cliem. ix. 213(1870). 

 1 Jour,,. CI,em.\S,:: xxiv. 639 (,871). 



m. Fl,.vs.[,l xxv. 386(1872). 



i Desaga, Fig. 1.078. 

 ' Jahresb.," 78(1868). 



connecting tube. The flow of gas is controlled by means of a 

 float in the other limb of the U-tube, which approaches or recedes 

 from the end of the gas-delivery tube. The float is held steady 

 by a guide needle, which is fixed to the upper extremity by means 

 of sealing-wax. He mentions Steling's regulator, but gives no 

 reference. 



Maiten.-on 1 (1S72) used an air-chamber 14 cm. long X 2 cm. 

 diam., and connected it by means of a fine tube with a modified 

 U-tube charged with mercury. The rough adjustment is made 

 by a fine opening in the narrow tube, which is closed by slipping 

 an india-rubber tube over it, and the final adjustment is made ty 

 means of the gas-delivery tube, which works air-tight through a 

 cork. A side branch to the U-tube serves as a by-pass. 



J. Myers - (1S72). — In this apparatus the air-vessel consists of 

 four tubes 15cm. long X 2 cm. diam. connected together by 

 small tubes, and which then communicate with a regulator similar 

 to that which Schlosing Uses. 



Cresti 3 (1S7S) employs a glass apparatus consisting of a hori- 

 zontal air-vessel 15 cm. long X 2 cm. diam. ; to this is attached 

 at right angles a glass regulator of the Bunsen-Kemp pattern, 

 the c jmmunication between the two being made by a capillary 

 tube which enters the upper part of the air-chamber of the regu- 

 lator. It is however a form of regulator which would require to 

 be well screened from draughts, as so much of it is exposed. 



Mercurial Thermometers (a). — Carmichael's 4 (1870) arrange- 

 ment consists of a tube 40 cm. long by 6 mm. diameter, closed 

 at one end, so that when filled with mercury it forms an elon- 

 gated thermometer. This is bent according to the bath in which 

 it is immersed, but is so arranged that the open end is vertical ; 

 near this end is affixed a side tube of 2 mm. diameter. This 

 tube, after bending upwards, bifurcates. Into the open end of 

 the larger tube a cork is fitted, through a hole in which a glass 

 rod slides. This rod serves as a regulator to adjust the level of 

 the mercury in the side tube. 



In Hannay's 5 (1S74) arrangement the principle is the same as in 

 the preceding, except that tbe adjustment is effected by means ol 

 a piston in the side tube, which is graduated, while the main 

 tube is bifurcated. It is open however to the objection that the 

 gas has to pass over heated mercury. 



Schlosing 1 ' (1S70) used a very fine tube of considerable length 

 (suitably bent) as the mercury reservoir, and led the open end 

 of it into one of the horizontal arms of a T-piece. The other 

 horizontal arm carried the inlet-pipe of the gas, which j assed to 

 the burner through the vertical arm. The escape of the mercury 

 from the reservoir was prevented by a piece of sheet india-rubber, 

 which was tied over the end of the tube. As the mercury ex- 

 panded it forced this elastic cap to assume a globular form, and 

 thus checked the supply of gas. '1 he quantity of mercury in the 

 reservoir was adjusted by means of a side-tube provided with a 

 stop-cock (Fig. 4). The outer tube of Fig. I is replaced by a 

 four-branched bulb which contains the extremities of the reser- 

 voir and of the gas entrance tube ; but these are separated by a 

 small wooden disk with a handle attached, which is fixed in the 

 upper branch, and which rests lightly on the india-rubber sheet. 

 The diameter of the gas tube no longer depends on that of the 

 india-rubber ; it can be larger, and the opening gaining in cir- 

 cumference can be diminished to become so narrow that the 

 slightest movement of the disk closes it. Total extinction of the 

 flame is prevented by a small radial groove on the disk. 



Reichert" (1S72) constructed his regulator by expanding the 

 top of the thermometer tube so as to form an elongated bulb. 

 In the top of this bulb was fixed the gas-inlet tube, which nearly 

 reached the lower extremity of the tulb. A side tube served as 

 gas exit. The adjustment was effected by means of a screw 

 which worked in a cap cemented on to a side tube in the stem of 

 the thermometer. 



Milne-Edwards 8 (1872) describes a regulator similar to 

 Reichert's, but dees not specify what shape or description of 

 bulb he employs. 



Schafcr's''' (1S74) is essentially the same as the preceding, 

 except that the inlet tube is a small steel tube with slit at lower 

 extremity. 



■ Fhirm. Zeit. /. Fuss, xi. 136 (1S72) ; ChetH. Cent,:, 513 (1872) ; Journ. 

 C/itV-o -So. xxvi. 471 (1S73). 



2 Deut.cheiH. Gcs. Be,: v. 859(1872); Chem. Sc-.vs. January 10, 1873. 



3 Cazz. Chim. /Int. viii. 292 (187S); Journ. Chem. Soc„ ,abst.. 294 

 (1879) * Client. A'ews. November 3, 1871. 



i Journ. Chem. See. xxvii. 206 (1S74). 



6 Ann. Clam, Fhys. [ 4 1 xix. 205 (1870) ; Fits. Zeitseli. ix. 477 (1870). 



7 P"gg- Ann. clxiv. 467 (1872) ; Fres. Zeitseli. xi. 34 (1872). 



8 Ann. Chim Phys. (4) xxv. 390 (1872). 



9 Quart. Journ Miero Sei. 394 (1874)- 



