51 Fifteenth Communication from Dr. Thornton, 



green crystals of nickel will then be obtained, which prove 

 that this metal was present in a considerable quantity ; 

 whereas, on the contrary, the crystals are of a reddish hue. 

 Remove the crystals, and let the fluid be repeatedly evapo- 

 rated and crystallized till the last crop of crystals are red. 

 The remaining fluid then contains no more nickel $ it may 

 therefore be crystallized. 



The obtained crops of crystals, which are more or less of 

 a beautiful red, should be put together, redissolved, and 

 recrystallized repeatedly, till a new crystallization does not 

 increase their beauty. 



The obtained green crystals of nickel are treated in a si- 

 milar manner till their green colour does not become more 

 lively by a fresh crystallization. These tedious processes 

 of crystallization may be considerably shortened if the ope- 

 rator picks his crops of crystals, or sorts and dissolves them 

 accordingly. 



The cobaltic solution of nickel, or the solution of nickel 

 soiled with cobalt, as it may be called, according to the 

 nature of the solution, may be purified respectively by sul- 

 phate of ammonia and subsequent repeated crystallizations; 

 a process which can by far more easily be adhered to in the 

 large wav than any of the methods now made use of. I 

 need hardly mention that both the salts may be decomposed 

 by carbonate of potash, and the carbonate of nickel and car- 

 bonate of cobalt be reduced in the usual way. 



XII. Fifteenth Communication from Dr. Thornton, 

 relative to Pneumatic Medicine. 



To Mr. Tilloch. 



May ao, 1804. 

 SITl, No. 1, Hind-streer, Manchester-square*, 



JL ii k following is an account of the efficacy of the oxy- 

 genated marine acid gas in a case of chlorosis or green sick- 

 ness ; and I have not any additional information to add, 

 although the cure was accomplished in the year 1795, be- 

 cause my success in such disorders has been uniform with 

 the simple oxygen gas orvital air, properly diluted, aided 

 by tonic medicines ; and this gas has little or no irritating 

 effect upon the lungs, which the other gas, if not properly 

 diluted, undoubtedly has ; and it is the part of the prudent 

 phvsician to apply the mildest means, when these are gene- 



rally found to answur. 



Letter 



