118 



Mr. Spencer U. Pickering on the 



It will be of interest to give the following table, comparing 

 the various hydrates isolated, together with their melting- 

 points, in the case of the three haloid acids, though in doing 

 so I am anticipating the publication of the results which I 

 have obtained with hydrogen iodide. The monohydrate of 

 hydrogen bromide was obtained in small quantities under 

 pressure by Roozeboom, and he also obtained indications of 

 the existence of a similar hydrate of hydrogen chloride : no 

 experiments have been made yet to ascertain whether the 

 iodide forms a monohydrate or not. As far as can be seen, 

 there appears to be no simple relationship between the freezing- 

 points of the various hydrates. 



m.p. 



m.p. 





m.p. 





m.p. 



HC1,H 2 ? H01,2H 2 O 

 HBr,H 2 ? HBr,2H o 

 HI, 2H 2 



-17-4 

 -11-2 

 -43? 



HCl, 3H 2 

 HBr, 3H 2 

 HI, 3H 2 



-24-8 



-48 



-48 



HBr, 4H 2 

 HI, 4H 2 



-55-8 

 -365 



Table I. — Densities of Solutions of Hydrogen Bromide 

 at 15°. Water at 4° = 1. 



Per cent. 

 HBr. 



Density. 



Per cent. 

 HBr. 



Density. 



First g 



ERIES. 



Second 



Series. 



65-186 



1-784496 



64-757 



1-776244 



63-931 



1-762986 



59-499 



1-680514 



63-465 



1-752372 



58-582 



1-664565 



62-310 



1-733345 



57-613 



1-648607 



61-545 



1-720028 



56648 



1-632845 



60-507 



1-700394 



55-761 



1-618365 



59-478 



1-681383 



53-949 



1-587695 



58-798 



1-669405 



53-029 



1-574158 



57-691 



1-651415 



52010 



1-558199 



56-458 



1-628475 



51-443 



1-545971 



55-701 



1-616653 



50 640 



1-535617 



54-813 



1-601491 



49-490 



1515815 



53936 



1-587476 



48-225 



1-498193 



52-723 



1-567934 



47-227 



1-483630 



51-494 



1-548080 



46431 



] -472454 



48-987 



1-509520 



45-372 



1-457340 



46-986 



1-479224 



44-349 



1-441741 



44-7985 



1-449141 







42-9777 



1-423322 







41-2954 



1-400219 







39-3818 



1-874766 







34-7356 



1-316402 







31-4824 



1-278364 







25-7661 



1-216692 







205357 



1-165279 







18-8511 



1-122792 





* 



10-2258 



1-075679 







5-4590 



1-038674 



















