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6 Dr. Thomson on the true Atomic Weight of [Jan. 



Chlorine 4*5 



Strontium 6*5 



Consequently muriate of strontian is composed of 



Muriatic acid 4*625 



Strontian 6*5 



11*125 



It is obvious, therefore, that the true weight of an atom of 

 Btrontian is 6'5, the very weight which I have already assigned. 

 The above experiment will neither succeed with Dalton's, Wol- 

 laston*s, nor Berzehus^s numbers — a sufficient proof that none of 

 them is absolutely correct. 



2. I made a great many trials before I was able to determine 

 the weight of an atom of hme ; but I consider it as needless to 

 relate those which were unsuccessful. Indeed I failed so fre- 

 quently that I for some time despaired of being able to deter- 

 mine the point. However by persevering and trying one method 

 after another, I at last hit upon a way which is quite easy, and 

 ■which, if carefully performed, yields most satisfactory results. 

 No salt of lime which I tried possessed sufficient solubility, and 

 the capacity of being totally deprived of water by heat without 

 decomposition. I was obliged, therefore, to have recourse to 

 calcareous spar. I took perfectly pure calcareous spar, reduced 

 it to a coarse powder, and exposed it for an hour to a tempera- 

 ture of between 300° and 400°, which renders it perfectly dry 

 "without disengaging any sensible quantity of carbonic acid. Ifc 

 will appear by the experiments which I am going to relate, that 

 pure dry carbonate of lime is composed of 



Carbonic acid 2*75 



Lime 3*5 



Carbonate of lime 6*25 



When pure crystals of bicarbonate of potash are exposed to. 

 a red heat in a crucible of platinum, one half of the carbonic 

 acid is driven off, and there remains pure and dry carbonate of 

 potash. Now this salt is composed of 



Carbonic acid 2*75 



Potash 6*00 



Carbonate of potash 8*75 



lowledge of the composition of these salts w 

 r easily to follow the experiments which I am 



6*25 grs, of dry calcareous spar were dissolved in muriatic 



The knowledge of the composition of these salts will enable 

 the reader easily to follow the experiments which I am going to 

 jelate. 



