182 Dr. "Turner on the Composition of Chloride of Barium. 



valent of chlorine, 70 as that of barium, and 78 as that of baryta. 

 The equivalent of chloride of barium is therefore 106; and on 

 mixing this quantity of the chloride with 88 parts of sulphate 

 of potash, each being previously dissolved in separate portions 

 of distilled water, he finds that the clear liquid left after the 

 insoluble sulphate of baryta has completely subsided, is not 

 rendered turbid either by muriate of baryta or sulphate of soda. 

 It is hence inferred, that by double decomposition the whole of 

 the baryta has united with all the sulphuric acid, and that all 

 the potash and muriatic acid are contained in solution in the 

 form of muriate of potash. The resulting sulphate of baryta, 

 after being collected and heated to redness, weighed exactly 

 118 parts; while the muriate of potash, when collected and 

 duly heated, yielded 76 parts of chloride of potassium. It 

 follows from this experiment that 40 is the equivalent of sul- 

 phuric acid, and 48 of potash; and on mixing with one equi- 

 valent of chloride of barium such a quantity of any soluble 

 sulphate as should produce a similar interchange of elements, 

 the constitution of that salt would be exactly determined. 



This leading experiment, from which Dr. Thomson deduces 

 the composition of chloride of barium as well as the atomic 

 weight of baryta, is maintained by Berzelius- to be inexact. 

 He prepared chloride of barium and sulphate of potash with 

 the greatest possible care ; and on mixing them in the pro- 

 portion mentioned by Dr. Thomson, he found that a consi- 

 derable quantity of the former, about 2*25 per cent, of the 

 amount employed, remained free in the residual liquid. (Lehr- 

 buch der Chemie, vol. iii. p. 106.) In an answer to this objec- 

 tion, published in the Philosophical Magazine and Annals of 

 Philosophy for last March, Dr. Thomson has maintained the 

 accuracy of his original experiment, stating that it had recently 

 been repeated by six of his practical pupils, and in no case did 

 the residual liquid contain a trace either of sulphuric acid or 

 baryta. I regret that my observations have forced me to a con- 

 clusion precisely opposite. I have made the experiment in 

 question repeatedly, with the greatest care, and with perfectly 

 pure materials, and in every instance the result coincided with 

 that obtained by Berzelius. The sulphate of potash which I 

 used was prepared by repeated crystallization from the crystals 

 of that salt as sold by the druggists, and was so pure that I 

 could not detect in it a trace of foreign matter. The chloride 

 of barium was formed by the action of pure muriatic acid on 

 native carbonate of baryta. The resulting solution was ren- 

 dered alkaline with pure baryta, in order to precipitate any 

 oxide of iron or manganese which might be present; and the 

 crystals subsequently obtained by evaporation were reduced to 



powder, 



