128 REPOET — 1886. 



to 570°. Here c was found as in all the other cases to be constant for 

 several pairs of temperatures compared for the same pressure for sulphur 

 and for oxygen ; and the calculated temperatures of oxygen agree with 

 the observed with an error of one degree at the most. 



Question of Applicabilittj of Hydrogen Thermometer to Low Temperatures. 



Wroblewski * objects that Olszewski's results cannot be true a,t very 

 low temperatures because at, for example, 61'5° (abs. temp.) = — 211'5° C. 

 at which the vapour-pressure found by Olszewski for hydrogen is 9 mm., 

 and at temperatures not quite so low as that, we must be getting 

 near the liquefying point of hydrogen, near enough at least to allow 

 of the suspicion that the behaviour of hydrogen may be getting irre- 

 gular, and deviating from the straight course prescribed by Amagat at 

 temperatures above 0° C. i.e. above 273° of absolute temperature. And 

 Wroblewski's criticism is probably just ; the determination of the lowest 

 temperatures is probably inaccurate ; but the points determined by 

 Olszewski, other than the very lowest temperatures, are probably very 

 accurate, as hydi'ogen evidently has a very low liquefying point, and is 

 far the most regular of the gases, as seen in Amagat's curves ; still 

 though we know from Amagat's results and from V. Meyer's that hydrogen 

 at ordinary tempei'atares and from these up to nearly 1700° C. behaves 

 in the most absolutely regular way in refei'euce to volume, |>ressure and 

 temperature, where at least the pressui'e is not excessively great, our 

 knowledge, however highly probable with regard to its behavioar at low 

 temperatures, is conjectural. 



Wroblewski used two thermo-junctions arranged as a thermo-pile, 

 one junction being kept at constant temperature, such as 0° or 100°, the 

 other in the liquid the temperature of which is sought, the temperature 

 being inferred from the deflection of the needle of a galvanometer. 



The elements of the pile were copper and german silver, and results 

 with the pile agreed with results with the hydrogen thermometer down to 

 — 193° C. ; but disagi-eed below that temperature. 



Other Formulce of Ramsay and Younr/. 



In the series of papers ^ the authors discuss two other formulae, which 

 might often be useful for getting fair approximations, but which do not 

 give such remarkably accurate results as the formula of which we have 

 been treating. 



A recent paper ^ gives applications of the formula (p. 125) to bromine, 

 iodine, and iodine monochloride. 



The Use of Formulce — Formula of Glausius — Formula of Van der Waals. 



The application of the principles of thermo-dynamics to many 

 chemical problems may be expected, as in the case we have enlarged 

 upon, to economise experimental work in this way ; a few data will be re- 

 quired, carefully worked out, and a whole set of experiments made with 



' Compt. Rerid. 100. p. 979. J.C.S. 1885, Abs. Aug. p. 861 ; cf. Comjit. Bend. 101, 

 p. 238 ; and J.C.S. 1885, Abs. Nov. p. 1101. 



2 pjiii_ ]\Jag. December 1885 and January and February 1886. 

 ' J.S.C. July 1886. 



