Mr. F. Guthrie on Salt Solutions and Attached Water. 15 



of crystals were analyzed. The final one was formed also 

 exactly at — 2°*7. 



Liquid. KN0 3 . per cent. 



(1) 8-8030 gave 0-9221 or 10-4 



(2) 1-6709 „ 0-1959 „ 11-7 



(3) 3-0300 „ 0-3350 „ 11-06 



(4) 4-2280 „ 0-4770 „ 11-2 

 The molecular relation is therefore about ] : 44-6. 



KN0 3 + 44H 2 0. 



§ 25. Cryohydrate of Sulphate of Copper. — The ordinary hy- 

 drates of blue vitriol are the mono-, bi-, and pentahydrates. 

 On cooling a saturated solution, the constant temperature of 

 solidification is found to be — 2° C. The last crop of crystals 

 being remelted, was evaporated and heated to the anhydrous 

 state. 



6*6952 grms. gave 1*1312 grm. CuS0 4 , or 16-89 per cent. 



This corresponds to the atomic relation of 1 : 43'7 (sayl to 44) 



CuS0 4 + 44H 2 0. 



Each crop of crystals, when melted, and the mother-liquor 

 present identically the same depth of colour. 



§ 26. Cryohydrate of Sulphate of Sodium. — A very great many 

 ordinary hydrates of this salt are known. I find that a saturated 

 solution has a solidifying-point at — o, 7 C. 



4-0630 grms. contained 1*850 grm. of Na 2 SO 4 , 

 or 4*55 per cent., 

 corresponding to the molecular ratio of 1 : 165*6 (say 1 to 166), 

 Na 2 S0 4 + 1 66 H 2 0. 



§ 27. Cryohydrate of Chlorate of Potassium. — The chlorate 

 of potassium, like the nitrate, has not hitherto been combined 

 with water. Almost the whole of the salt separates out in 

 the anhydrous state when a saturated solution is cooled to 

 0° C. On further cooling to —3° C, the solution may pre- 

 sent a remarkable condition of double supersaturation. If at 

 this temperature a crystal of anhydrous chlorate is dropped in, 

 anhydrous chlorate is formed in considerable quantity. If an 

 ice fragment is introduced, ice only is formed. If both are 

 thrown in, both are formed, the one set of crystals floating, 

 the other sinking. If the temperature of the supersaturated 

 solution be further cooled, the proper cryohydrate separates 

 out and the temperture rises to — 0°*5. The normal formation 

 ensues on introducing a crystal of the cryohydrate from one 

 crop to start the formation of the next. This phenomenon, 

 which is not without its counterpart in some other cases, argues 

 forcibly for the existence of a distinct crystalline form proper to 

 the cryohydrate. 



