and Attached Water. 



365 





Table XXIV. 





NH 4 N0 3 



per cent, by 

 weight. 



H 2 



per cent, by 

 weight. 



Temperature 

 Centigrade at 

 which solidifi- 

 cation begins. 



Nature of 

 solid formed. 



10 



90 



o 

 - 3-5 



Ice. 



20 



80 



- 7 



»» 



30 



70 



— 11-5 



ii 



40 



60 



-17-0 



>> 



437 



56-3 



-17-2 



Cryohydrate. 



47 



53 



-120 



NH 4 N0 3 . 



51 



' 49 



- 57 



n 



541 



459 



00 



>i 



(Kar.) 66-5 



43-5 



+18-1 



ii . 



The solubility at 18 0, 1 is the observation of Karsten. The 

 shape of the tracing of this salt bears a remarkable resemblance 

 to that of nitrate of potassium (see fig. 1). The gradual 

 slope of its right-hand branch enabled me to insert two deter- 

 minations there. Also noteworthy is the comparison between 

 the tracing of this salt and that of the sulphate of the same 

 base. Running together with near coincidence down to their 

 cryohydrates, which are nearly identical in temperature and 

 not far apart in percentage of salt, the one rises more abruptly 

 than any other curve ; the other is, with one exception, the 

 most gradual. 



§ 136. Separation of Ice and Hydrated Sulphate of Magne- 

 sium from the solutions of that salt. — The analysis of crystallized 

 sulphate of magnesium in regard to its water by direct estima- 

 tion is rather unsafe, on account of the high temperature re- 

 quired to drive off the last traces of water, and the decomposi- 

 tion of the salt at a somewhat higher temperature. I there- 

 fore determined the sulphuric acid in a sample of the sulphate 

 I was about to use, and found that it was nearly the so-called 

 hepthydrate. The determination of the solubility at 0° C. was 

 also derived from a sulphuric-acid determination. Taking 

 every 1*96 grm. of the crystallized salt as containing 1 grm. 

 of MgS0 4 , the following solutions were examined : — - 



