iydroua salt. 



Per cent. 



6-5874 



2-871 



0-5910 



3-013 



0-5249 



2-663 



0-5318 



2-693 



0-3718 



2-943 



38 Frederick Guthrie on Salt Solutions 



different preparations. In each ease several crops of the solid 

 cryohydrate had been removed. 



grams. 



20-4624 . . . 



19-6134 . . . 

 19-7115 . . . 

 19-7476 . . . 

 12-6320 . . . 

 The mean of these rather discordant results shows a water- 

 worth of 608-3 (K 2 Mn0 8 ). 



As a ervogon, permanganate of potash gives a temperature 

 of -0 c -52. 



§ 172. Acetate of Lead. — The cryohydrate of acetate of lead 

 forms at — 1°*4 C. After the separation of several crops, in each 

 case the residual liquids, after weighing, were repeatedly eva- 

 porated with an excess of nitric acid and gently heated. It is 

 found that the acetate is thereby completely converted into 

 the nitrate. 



grams. Nitrate. 



Per cent, 

 of acetate. 



14-8195 gave 2*7906 



= 18-4 



6-9029 „ 1-2401 



= 17-5 



7-4904 „ 1-3700 



= 18-0 



The water-worth, calculated on the mean of these three 

 results, is 82'3. The temperature of the acetate-of-lead cryo- 

 gen is — 1°*7. 



§ 173. Sulphate of Zinc and Potassium. — The cryohydrate 

 forms at — 1°*25. The analyses are, as before, of different 

 residual liquids. The liquid cryohydrate was evaporated to 

 dryness at 100° and heated to incipient fusion. 



grams. ZnS0 4 +K 2 S0 4 . Percent. 



9-1020 yielded 0*7274 or 7*992 

 9-0934 „ 0-7739 „ 8-510 



The mean of these results gives the water-worth 167*4. As 

 a cryogen, the same double salt gives — l c, 01. The tempera- 

 ture of solidification of this cryohydrate and the percentage of 

 salt it contains are approximately those of K 2 S0 4 , its least- 

 soluble constituent (see §§ 22, 71). 



Temperature of 



Per cent. 



crvo hydrate. 



of salt. 



K 2 S0 4 .... -l°-5 



7*8 



ZnS0 4 .... -7° 



30*84 



: 2 S0 4 +ZnS0 4 .... -j°*25 



8*25 



mparing this fact with those developed 



in §§ 109-120, 



