and Attached Water. 53 



on till — 10° C. was reached, when the whole was pasty. At 

 — 13° the mass was not yet dry. At — 14 0, 5 it was nearly dry. 

 At -16°-5 to -17° it became perfectly dry. We find then 

 that 



The cryohydrate of KN0 3 solidifies at - 2- 7 

 NaM) 3< „ -17-5 



„ „ equiv. mixture „ — 7 to —17°. 



Hence it appears that the presence of the nitrate of sodium 

 lowers the temperature at which the cryohydrate of the nitrate 

 of potassium is formed, while the temperature of final solidifi- 

 cation is virtually as low as when the nitrate of sodium was 

 alone present. 



§ 111. Mixed Nitrates of Potassium and Sodium as Cryo- 

 gen. — The powdered nitrates being mixed in the same propor- 

 tion as in § 110, namely 11*22 grms. of KN0 3 and 9'44grms. 

 of NaN0 3 , and stirred with about 80 grains of crushed ice, gave 

 a temperature of — 16°*8. This is clearly again due to the 

 more powerful cryogen NaN0 3 , which (§ 75) gave — 16°*5. 



§ 112. Mixed Chlorides of Potassium and Sodium as Cryo- 

 hydrate and Cryogen. — Taking the salts in monomolecular 

 ratio, namely of 



KC1 taking 18-625 

 NaCl „ 14-625 

 dissolving in water and allowing it to stand until crystalliza- 

 tion just began, a solution was obtained which solidified com- 

 pletely at —21° C. On mixing the mixture of the same salts 

 in the same proportion with crushed ice, the resulting tempe- 

 rature was — 21°*8. The temperatures in both cases are evi- 

 dently governed by the action of the NaCl ; for 



The cryohydrate of KC1 solidifies at —11*4 

 „ NaCl „ -22 



„ „ equiv. mixture „ —21 



Temperature of KC1 as cryogen —10*5 

 „ NaCl „ -22 



„ equiv. mixture „ —21 



There is so much difficulty attending the accurate separation 

 of sodium and potassium that no method of analysis of them 

 with which I am acquainted is free from the possible error of 

 2 or 3 per cent, upon the quantity. Accordingly, for the 

 quantitative study of the mixed cryohydrates or cryohydrate of 

 the mixed salts, the following two simple ones were chosen. 



§ 113. Mixed Chlorides of Potassium and Ammonium as 

 Cryohydrates and Cryogens. 



Of NH 4 CI were taken 13*375 grms. 

 „ KC1 „ 18-625 „ 



