1820.] the Atoms of Barytes, Potash, Soda, Sfc. 333 



escape the test of the experiment which I have now stated must 

 be very small indeed. 



I shall now show by another similar experiment that the 

 weight of an atom of soda is precisely 4. 



1 atom of sulphuric acid = 5 



1 atom soda = 4 



1 atom anhydrous sulphate of soda. = 9 

 1 atom chloride of barium =13*25 



Take pure crystals of sulphate of soda, dry them in a platinum 

 crucible on the sand bath, then expose the dry residue to a red 

 heat for half an hour. Dissolve in distilled water 9 grs. of this 

 dry salt. Dissolve in another portion of distilled water 13*25 

 grs. of dry chloride of barium. Mix the two solutions well toge- 

 ther. When the sulphate of barytes has fallen to the bottom 

 draw off the clear liquid by means of a sucker, and examine it, 

 for barytes and sulphuric acid, in the manner stated above. No 

 traces of either substance can be found in it. It is clear, there- 

 fore, that 9 grs. of anhydrous sulphate of soda contain exactly 

 as much sulphuric acid as 11 grs. of sulphate of potash. Both 

 contain precisely 5 grs. of true sulphuric acid ; consequently if 

 an atom of potash weigh 6, an atom of soda must weigh 4. It 

 will be seen by consulting the fifth edition of my System of 

 Chemistry, that the number 4 is derived very nearly from the 

 different experiments undertaken to determine the composition 

 of soda. 



If we apply this experimental method to the examination of 

 the atomic weights given by Dalton, Wollaston, and Berzelius, 

 we shall find that none of them are exact. 



I have not been able to succeed in these experiments when I 

 used crystals of sulphate of soda. From the analysis of these 

 crystals by Berzelius, it follows that they are composed of 1 atom 

 sulphuric acid, 1 atom soda, and 10 atoms water. Now 



1 atom sulphuric acid = 5-00 



1 atom soda = 4*00 



10 atoms water =1 1*25 



20-25 



So that 20-^- grs. of crystals of sulphate of soda ought to be 

 exactly equivalent to 9 grs. of anhydrous sulphate. But when 

 we mix together a solution of 20*25 grs. of crystals of sulphate 

 of soda and 13*25 grs. of chloride of barium, and examine the 

 clear liquid after the separation of the sulphate of barytes, we 

 always find that it contains an excess of barytes. It is obvious 

 from this that the crystals of sulphate of soda contain more than 

 10 atoms of water. I would have investigated the real quantity 

 had I not been stopped by a circumstance which it does not 



