and Attached Water 



213 



drate also melts at the same temperature (I found — o, 9)« 

 Owing to this short range of temperature it is impossible 

 to examine the separation of ice from solutions of various 

 strengths. The determinations were made by reducing the 

 salt to a bibasic pyrophosphate of sodium. For the cryohy- 

 drate, 



1. 2. 



Solution . 6-5760 9-34011 



Na 4 P 2 7 . 0-1119 0-1627 j 



The water-worth is accordingly 852. 



The following gave the solubility at 0° C. : — ■ 



6-7277 grms. of solution gave 0-1264 of Na 4 P 2 7 , or 2*0 per 

 cent, of Na 2 H P0 4 . 



§ 151. Separation of Ice Sfc. from Solutions of Nitrate of 

 Sodium. 



Table XXXI. 



Mean per cent. 

 l-72ofNa 4 P 2 7 , or 

 1-83 of Na 2 HP0 4 , 



NaN0 3 per 

 cent, by weight 



H 2 O per cent, 

 by weight. 



Temperature 

 at which solidi- 

 fication begins. 



Nature of solid. 



5 



95 



o 



- 2 



Ice. 



10 



90 



- 4-2 



n 



15 



85 



- 6-3 



»» 



20 



80 



- 8-4 





25 



75 



-10-8 



it 



30 



70 



-13 



ii 



35 



65 



-15-5 



it 



40-80 



59-2 



-17-5 



Cryohydrate. 



42-34 



57-66 



{ 



NaN0 3 or sub- 

 eryohydrate. 



There appears to be a subcryohydrate of a composition in- 

 termediate between 40*80 and 42*34 per cent. For the deter- 

 mination of the composition of the cryohydrate I refer to § 75. 

 The solubility at 0° C. was derived from the data ; 6*0660 of 

 solution gave 2*5682 of NaN0 3 . It is remarkable that Marx 

 found 44*4 per cent, and Poggiale 44*3 per cent, of the anhy- 

 drous salt. The salt I employed was made from the pure bi- 

 carbonate, and was entirely free from sulphates and chlorides. 

 As in all similar determinations, I was not content to surround 

 the flask containing the nitrate with ice ; for I never find that 

 by this means the temperature in the flask sinks to 0° C. A 

 few grains of salt are added to the ice ; and the temperature, as 

 indicated by a continually agitated thermometer in the solu- 

 tion, remains for four or five hours at 0° C. 



§ 152. Separation of Ice Sfc. from Solutions of Nitrate of 

 Lead. 



