DR. TURNER ON CHLORIDE OF BARIUM. 295 



lution which precipitated barytic salts freely, and afforded certain evidence of 

 the presence of potash with muriate of platinum. 



The presence of sulphate of potash was at first naturally ascribed to im- 

 perfect edulcoration ; but as it was still found, even after the precipitate had 

 been washed with unusual care, I was led to examine the subject minutely. 

 A solution of sulphate of potash was mixed with a large excess of muriate of 

 baryta ; the insoluble sulphate was edulcorated until the washings ceased to 

 contain a trace of baryta, and was then collected on a filter, and ignited. On 

 boiling it in powder with water, sulphate of potash was dissolved. The expe- 

 riment was varied by mixing the solutions at a boiling temperature, and con- 

 tinuing the ebullition for some minutes ; but the result was the same as before. 

 On edulcorating the precipitate with boiling water, sulphate of potash begins 

 to make its appearance in the washings as soon as the excess of muriate of 

 baryta has been removed ; but neither by this means, nor by boiling the re- 

 cent precipitate for hours in successive portions of distilled water, have I suc- 

 ceeded in removing all the sulphate of potash. The adhesion of this salt ensues 

 even in a dilute solution ; and it is not prevented by the presence of other 

 salts, such as nitre, and nitrate or muriate of ammonia, nor by free muriatic 

 acid. The quantity of adhering sulphate of potash is variable, depending ap- 

 parently as well on the relative quantity of the two salts, and the strength of 

 the solution, as on the manner and extent of edulcoration. I have known it to 

 increase the weight of the sulphate of baryta by one per cent. 



The foregoing observations, unless I am much deceived, will fully justify the 

 statement, that Dr. Thomson's method of analyzing chloride of barium is 

 radically defective. For if chloride of barium and sulphate of potash be 

 mixed in the proportion to make a perfect interchange, some of the former will 

 remain in the liquid, proportional to the quantity of the latter which escapes 

 decomposition ; whereas the absence both of sulphuric acid and baryta from 

 the liquid can only occur, when the quantity of chloride of barium is insuf- 

 ficient for effecting complete double decomposition with the sulphate of potash. 

 So that when the proportions appear to be right, they are certainly wrong ; 

 and they may be right, when they appear to be wrong. It is obvious, too, that 

 Dr. Thomson's analysis of sulphate of potash by means of chloride of barium, 

 is not more satisfactory than his analysis of chloride of barium by sulphate of 



