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



(1) 13*2512 grms. of cryohydrate gave 03912 grm. KCi0 8 > 



or 2'95 per cent. 



(2) 13-5810 grms. of cryohydrate gave 03915 grm. KC10 3 , 



or 2'88 per cent. 



The molecular relation is exactly 



KC10 3 + 222H 2 0. 



§ 28. Cryohydrate of Bichromate of Potassium. — I chose this 

 salt because it is not constructed on the ordinary salt type. I 

 found it solidified entirely at — l u C. The crystals, whieh are 

 at first transparent, become opaque, and are of a bright straw- 

 yellow. 5.4968 grms. gave 0-2868 K 2 Cr 2 e 7 , or 5*305 per cent. 



This gives the largest ratio of water, namely 

 K 2 Cr 2 7 + 292H 2 0. 



As with the sulphate of copper, so in this case all crops of 

 crystals, when melted, had exactly the same depth of colour. 



§ 29. Sources of error. — I need scarcely point out that the 

 molecular ratios derived from the above experiments can only 

 be considered provisional. In the case of bodies which com- 

 bine with as many as forty and upwards molecules of water, a 

 very slight error in the determination may make a difference of 

 one or two molecules of water. In those which have a very low 

 solidifying-point, another source of error creeps in. The liquids, 

 even on pouring from one vessel to another, dilute themselves by 

 condensing moisture from the air. With due regard to the pro- 

 bable direction of error in each case, I venture to submit the 

 following tabulation, showing in column 1 the anhydrous salt, 

 in 2 the temperature Centigrade of solidification, in 3 the 

 actual percentage of anhydrous salt found, and in 4 the num- 

 ber of molecules of water to one of salt. 



Table VIII. 

 Temperature of Solidification and Molecular Ratio of Cryohy- 

 drate s. 



0) 



(2) 

 Temp. Cent. 



(3) 



Per cent, of 

 salt. 



(4) 



Molecules of 



water to 1 of 



salt. 



NaCl 





 -23 

 -15 



- 7 



- 6 



- 27 



- 2 



- 07 



- 0-5 



- 10 



23-603 



19-56 



30-84 



21-86 



11-20 



16-89 



455 



2-93 



5-306 



10-5(?10) 



12-0 



200 



240 



44() 



410 

 1H6-0 

 222-0 

 292-0) 



NH 4 C1 



ZnSO l 



MeSO 



KN0 3 



CuS0 4 



Na S0 4 



KCIO3 



(K Cu„0„ ., 





