Prof. Graham on Water as a Constituent of Salts. 417 



The quantities of the powders which I have hitherto em- 

 ployed have been too small, (not exceeding 30 or 40 grains,) 

 to decide upon their electrical states in a satisfactory manner. 



Before I conclude the present communication, I will ad- 

 vert to a simple experiment, which is familiar to many, I have 

 no doubt, and which bears upon the subject under considera- 

 tion. 



Thus : take up a small portion of tallow at the end of a 

 wire; hold the latter inclined to the horizon and with the hand 

 uppermost; thrust the tallow into the flame of a candle, and it 

 will be seen to react from the heat and run up the wire, in a 

 melted state, to the distance of an inch or more. Professor 

 Stevelly alluded to this experiment in reference to the repul- 

 sive agency of heat, at the meeting of the British Association 

 in Edinburgh. 



Kensington, January 6, 1 835. 



LXVI. On Water as a Constituent of Salts, In the Case ofSul- 

 phates. By Thomas Graham, F.R.S.E., Andersonian 

 Professor of Chemistry and Vice-President of the Philoso^ 

 phical Society of Glasgow. 



[Continued from p. 334, and concluded.] 



Sulphate of Zinc with Sulphate of Soda : Zn'S(NaS) + H\ Sul- 

 phate of Zinc and Soda. 



T^HIS salt, I believe, has not hitherto been described. I 

 -■- failed in attempting to form it, by dissolving together 

 sulphate of zinc and sulphate of soda in atomic proportions : 

 the salts uniformly crystallized apart, either in cold or in warm 

 weather. Each of the salts was also added in excess to the 

 other, but with no better effect. It appears, then, that sulphate 

 of soda does not displace the saline water of sulphate of zinc, so 

 easily as sulphate of potash does. But the desired salt was 

 obtained by a process of double decomposition, suggested 

 from consideration of the relations of the sulphates. Solu- 

 tions of bisulphate of soda, and of sulphate of zinc, were 

 mixed together in atomic proportions, from which the sul- 

 phate of zinc and soda separated in a gradual manner in the 

 course of a day or two, leaving sulphuric acid in solution. 



Sulphate of zinc with saline "j f Sulphate of zinc with sulphate of 



water, I • ijJ soda. 



Sulphate of water with sul- j ^ j Sulphate of water with saline 



phate of soda, J I water. 



This salt is deposited in distinct tabular crystals, of a pecu- 

 Third Series. Vol. 6. No. 36. June 1 835. 3 H 



