﻿144 M. C. Marignac on the Specific Heats, Densities, 

 H 2 OS0 3 . I found:— 



c=0*3315 between 17° and 22° • 

 c=0*3363 „ 20 „ 56. 



These numbers confirm one another, their difference being j ust 

 that which should result from the difference of the temperatures. 

 Previous determinations had given : — 



0-3095, Person*. 



0*343 between 21° and 46°, H. Koppf. 



0*3413 „ 13 „ 77, Pfaundler J, old determinations. 



0*355 „ 22 „ 80, Pfaundlerj, recent experiments. 



It may also, by analogy, be concluded, from the whole of the 

 observations of the last- mentioned savant with respect to the 

 highest temperatures, that the result would have been about 

 0-352 between 22° and 60°. 



We see that my results are a little lower than those obtained 

 by MM. H. Kopp and Pfaundler. Supposing that they used 

 in their experiments sulphuric acid merely concentrated by pro- 

 longed boiling, this alone would go far to explain the difference. 

 In fact, such an acid contains ^ of an equivalent of water too 

 much. We should therefore have, starting from the result I 

 obtained for the monohydrated acid (namely, c = 0*3363 and 

 C = 33):— 



99*5 for the molecular weight of the acid concentrated by 

 boiling, 



34*5 for its molecular heat, and 

 0*3467 for its specific heat. 



H 2 0, SO 3 + Aq. I find c= 0*4411 between 20° and 56°. 



This result agrees exactly with the last observations of M. 

 Pfaundler ; for he obtained 



0*447 between 22° and 80°, 

 0-444 „ 22 „ 70. 



H 2 0,S0 3 + 5Aq. I obtained 



0*5764 between 15° and 19°, 

 05833 „ 20 „ 56. 



The difference between these results appears to correspond 

 well with that between the temperatures. 



The results, therefore, of these determinations seem to me to 

 confirm those of the first series. 



It will moreover be remarked that these experiments confirm 



* Ann. de Chim. et de Phys. S. 3. vol. xxxiii. p. 437. 



t Pogg. Ann. vol. lxxv. p. 98. 



% Joum.furprakt. Chem. vol. ci. p. 507. 



§ Berichte der Deutsch. chem. Ges.zu Berlin, 1870, p. 798. 



