Intelligence and Miscellaneous Articles. 235 



sent lime, a little magnesia, soda, potash, traces of iron, phosphoric 

 acid, chlorine and sulphuric acid. — Journ. de Pharm. et de Ch., De- 

 cembre 1845. 



ON THE DOUBLE SALTS OF THE MAGNESIAN GROUP. 



M. J. Isidore Pierre has paid particular attention to the salts of 

 this group, including those of magnesia, oxide of copper, zinc, nickel, 

 cobalt, manganese and iron. 



The author observes, that it is well known that Prof. Graham has 

 stated, with respect to the sulphates of the above-named bases, that 

 one of the equivalents of water cannot be eliminated, except at a 

 much higher temperature than is required for the others ; that this 

 equivalent may be replaced by an equivalent of a salt, so that the 

 double salt formed contains one equivalent less of water than if each 

 of the two simple sulphates had brought all its water of crystalliza- 

 tion into the molecule of the double salt which results from their 

 combination. 



M. Pierre states that the results which he has obtained do not 

 confirm those of Prof. Graham ; he found that sulphate of zinc con- 

 tains, as generally admitted, 43*72 per cent., or seven equivalents of 

 water ; and he ascertained that by exposing it for a long time to a 

 temperature of 230° Fahr. and a current of dry air, that it lost 43" 6 

 per cent., or the whole of its water, which is at variance with Gra- 

 ham's result, who found that it required a heat of 400° Fahr. to ex- 

 pel the seventh equivalent of water. 



Double Sulphate of Zinc and Potash. — This salt is readily prepared 

 by mixing together hot solutions of equivalents of sulphate of zinc 

 and bisulphate of potash, and allowing crystallization to take place. 

 The crystals are beautiful small, milk-white parallelogrammic tables ; 

 this salt is soluble in two and a half times its weight of boiling water, 

 but much less soluble in cold water, for it crystallizes abundantly 

 on the cooling even of an imsaturated solution. 



When exposed gradually to a heat of 356° to 392° Fahr., it efiio- 

 resces without fusing in its water of crystallization, which it loses 

 completely and pretty rapidly at this temperature, the amount being 

 27'49 per cent. The author's analysis gives as the formula of this 

 salt, ZnO, SO 3 ; KaO, SO 3 + 7HO, which indicates," as he shows, 

 27*32 per cent, of water instead of 24*49, the experimental result. 



In this case it is therefore to be remarked, that the sulphate of 

 zinc retains the seven equivalents of water which it possessed in its 

 simple state. 



Double Sulphate of Zinc and Magnesia. — M. Pierre observes, that 

 it is generally supposed that these two sulphates may combine in all 

 proportions ; having found that sulphate of zinc in the double salt 

 which it forms retains its seven equivalents of water, the author ob- 

 serves that if sulphate of magnesia did the same, the double Bait 

 should contain fourteen equivalents of water. 



This salt is readily obtained by mixing its equivalents and crystal- 

 lizing; it forms very fine oblique rhombic prisms, which are by 



