and Attached Water. 



41 



up the anhydrous salt until — 0°*45 was reached; then the 

 cryohydrate was formed. The amount of salt was determined 

 by evaporation over sulphuric acid in vacuo. 



grams. Cyanide. 



3-8835 gave 0*2892 or 7-45 per cent. 



5-0238 „ 0-3738 or 7-44 „ 



This percentage exhibits the water-worth of 174. The same 

 salt as a cryogen reaches the temperature — U *6. 



§ 180. Acetate of Zinc. — 'A boiling saturated solution was 

 allowed to cool to the atmospheric temperature ( + 15°). The 

 residual liquid was drained from the separated crystals and 

 introduced, together with a few crystals, into a stoppered 

 bottle. After keeping in ice for nine hours with frequent agi- 

 tation, all sign of further crystallization ceased. The zinc was 

 estimated by precipitation with carbonate of sodium. It was 

 thus found that the strength at 0° was 23 per cent. This so- 

 lution, when artificially cooled, yields fern-like crystals at 

 — 5°*9 ; these gradually became opaque, the opacity forming 

 in a frond-like manner ; the whole became dry at the above 

 temperature. An analysis of the residual liquid, after two 

 crops of cryohydrate, showed that the cryohydrate had sensibly 

 the same composition as the solution saturated at 0° C; for 



grms. Oxide. 



5-9980 gave 0*6103 or 23 per cent, anhydrous acetate. 



§ 181. Hyposulpldte of Soda. — The following are the tem- 

 peratures at which solidification begins in solutions of varying 

 strengths of this salt : — 



Table XXXIX. 



N 2 S 2 3 , 



by weight. 



Temperature, 

 Centigrade. 



Body found. 



per cent. 









1 



- 01 



Ice. 



2 



rr- 04 





3 



- 0-65 





5 



- 1-2 





6 



- 1-5 1 



Appearance of ice, but sinks 



10 



- 2-5 



in water at 0°. Perhaps 



15 



- 3-9 y 



due to interstitial solution. 



20 



- 5-45 



More probably a subcryo- 



30 



- 9-5 to -110 J 



hydrate. 



30 



-11 



Cryohydrate. 



33-5-5 

 41 



, 20 f (-^ reraers )- 



Ordinary hydrate. 



A 30-per-cent. solution does not always give up a solid at 

 — 9°-5. Sometimes the temperature sinks to — 12°'4; then 



