||k Dr: Thomson on the true Atomic Weight of [Janj 



linoe 'Still remained in Bolution; consequently the carbonate of 

 patash had not been sufficient to throw down all the lime. We 

 i^ee from this that an atom of lime is not so heavy as 3*625. 



(2.) The nearest multiple of 0*125 to Mr. Dalton's atomic 

 weight of Ume is 3*375. Now if this be the weight of an atom 

 of hme, it is plain that dry carbonate of hme must be com- 

 posed of 



Carbonic acid 2*75 



Lime 3-375 



Carbonate of Hme 6*125 



To verify this supposition, I dissolved 6*125 grs. of carbonate 

 ef lime in muriatic acid, and after treating the solution in the 

 manner already described, I mixed it with a solution of 8*76 

 gw.' of carbonate of potash. After the carbonate of lime had 

 »ttbsided, the clear supernatant liquid was not precipitated br 

 oxalate of ammonia, and, therefore, contained no lime ; but it 

 instantly rendered cudbear paper violet, and therefore contained^ 

 an excess of potash. Hence the muriatic acid united with the 

 lime had not been sufficient to saturate the whole of the potash. 

 It is clear from this that an atom of lime is heavier than 3-375. 



These experiments are sufficient I trust to satisfy the reader 

 tbat the true weight of an atom of lime is 3*5. 



3. 1 found much less difficulty in determining the weight of 

 aw atom of magnesia than of hme. Sulphate of magnesia may 

 b*er^xposed to a red heat, and rendered thoroughly dry without, 

 losing any of its acid, if the experiment be properly conducted.- 

 Jf' the weight of an atom of magnesia, which I have assigned, 

 namely, 2*5 be correct, it is obvious that anhydrous sulphate of 

 DBftgnesia is composed of 



Sulphuric acid 5*0 



Magnesia 2*5 



Sulphate of magnesia 7*5 



Anhydrous chloride of barium, as I demonstrated in a former 

 paper, is composed of 



Chlorine * 4*5 



Barium 8*75 



< Chloride of barium 13*25 



7^ grs. of anhydrous sulphate of magnesia, and 13*25 grs. of, 

 chloride of barium, were respectively dissolved in two distincJL 

 portions of distilled water, and the solutions mixed together^. 

 Mid well agitated. After the sulphate of barytes had subsided, a 

 portion of the clear liquid was drawn off and examined : neither 

 sulphate of soda nor nitrate of barytes occasioned any precipitate 

 or muddiness in it. Hence it is obvious that the liquid neitheXt. 



