1(58 On the Daltonian Theory of [Sept. 



Number of Weight of an 



atoms. integrant particle. 



135. Hydrate of potash . . . . 1 p + 1 "> 7*152 * 



136. Hydrate of soda 1 s + 1 w 9*014 b 



1S7. Hydrate of lime 1 / + 1 w 4*752 c 



138. Hydrate of barytes... 1 b + 1 w 10-863 d 



139. Hydrate of strontian . .1 st + 1 w S*0S2 e 



MO. Hydratcof magnesia . .2 m 4- 1 w 5*868 f 



* By hydrate ofpotash^ I mean caustic potash which has been 

 exposed to a read heat. If we suppose it composed of an inte- 

 grant particle of potash, and an integrant particle of water, it 

 should consist of 100 potash + 18-867 water. Now Davy, by 

 heating potash and boracic acid together, actually separated 

 between 17 and 18 of water. This I consider as a full confirma- 

 tion. Berzelius obtained 16 per cent. Larlok i Kemien, ii. 

 594 ;) which is very nearly the exact quantity. It ought to have 

 been 15-872. 



b This is caustic soda exposed to a red heat. Supposing it a 

 compound of anint errant particle of soda and of water, it ought 

 to consist of 100 soda + 1 4-362 water, or 84'128 soda + 

 12-558 water. I do not know that any accurate experiments 

 have been made to determine the proportions of this hydrate. 



c According to this statement, slacked lime (which is the 

 hydrate) is composed of 100 lime + 61*27 water. Now Lavoi- 

 sier found it composed of 100 lime -f- 28*7 water, and Dalton 

 oflQOlime 4- 33-333 water. The mean of these results gives 

 us 31-016, which very nearly coincides with the number in the 

 table. 



d By comparing the experiments of Berthollet (Mem. d'Ar- 

 cueil, ii. 42,) with those of Berzelius, (Ann. de Chim. lxxviii. 

 50,) it appears that crystallized barytes exposed to a red heat 

 (hydrate of barytes) is composed of 100 barytes -f 12*121 water. 

 If we suppose it a compound of an atom of barytes and an atom 

 of water, its composition will be 100 barytes + 11-632, which 

 almost coincides with experience. Hence the number in the 

 table. 



e That a hydrate of strontian exists is certain, but no direct 

 experiments have been made upon its composition ; but from 

 analogy, it is probable the number in the table is correct. The 

 crystallized hydrate, according to Dr. Hope's experiments, is 

 composed of 1 atom strontian and 13 water. 



f Hydrate of magnesia is obtained by precipitating magnesia 

 from an acid, by means of potash, and drying it in a gentle heat. 

 It is composed, according to Davy, of 100 magnesia + abou t 



