350 Mr. Daniell on a Neva Register-Pyrometer^ 



of the gas evolved from fully hydrated oxalic acid when de- 

 composed by heat. According to my observation, the ratio of 

 carbonic oxide to carbonic acid is always nearly as five to six. 

 A similar mixture is evolved from the acid after two-thirds of 

 its water has been withdrawn, provided the heat be slowly 

 applied; but when the decomposition is very rapid, I have 

 generally obtained a still smaller proportion of carbonic 

 oxide. On one occasion this gas did not exceed 31 per cent. 

 The statement of M. Gay-Lussac relative to the appearance 

 of formic acid, and the explanation which he gives of its pro- 

 duction, appear to me perfectly correct. 



XLIV. On a new Register-Pyrometer, Jor Measuring the 

 Expansions of Solids, and determining the higher Degrees 

 of Temperature upon the common Thcrmometric Scale. By 

 J. Frederic Daniell, Esq. F.R.S. 



[Concluded from p. 279.] 

 T SHALL now collect together the results of the preceding 

 ■*■ experiments, for the purpose of showing what conclusions 

 may be derived from them with regard to the degrees of tem- 

 perature which they indicate when referred to the common 

 thermometric scale. I shall make the calculations first upon 

 the supposition that equal amounts of expansion denote equal 

 increments of temperature ; and I shall thus be enabled to 

 compare the present series with that which I formerly obtained 

 ■with my first pyrometer, and to offer a few remarks upon the 

 differences of the two. 



I shall adopt the corrected temperature of 6G2° (350° cen- 

 tigrade) for the boiling point of mercury, as proposed by 

 MM. Dulong and Petit; which agrees very closely with the 

 amount employed in my first calculations, and which, deduct- 

 ing 62° for the mean temperature at which my experiments 

 commenced, gives 600° for the interval tor which the several 

 expansions were determined. 



The first column of the following Table refers to the num- 

 ber of the experiment ; the second to the mark of the register 

 and the bar which was employed ; and the third to the amount 

 of expansion in the same, occasioned by boiling mercury, or 

 600° of temperature upon Fahrenheit's scale. The fourth 

 column exhibits the arc measured upon the scale; and the 

 fifth the equivalent expansion. The sixth contains the cor- 

 responding temperature ; the seventh records the state of the 

 metal, which was the object of the experiment; and in the 

 eighth I have recapitulated the corresponding results of my 

 former Essay. 



Table 



