1820'.] Pht/skal Science during the Year 1819. 13 



rine is converted into muriatic acid ; so that water is decom- 

 posed, the sulphur combines with its oxygen, while the chlorine 

 unites with its hydrogen. When the liquid is saturated with 

 ammonia, we obtain hyposulphite of ammonia, and muriate of 

 iammonia. Nitrate of silver, when dropped in, throws down the 

 muriatic acid, and decomposes the hyposulphite of ammonia, 

 forming a hyposulphite of silver, which gradually undergoes 

 spontaneous decomposition, and is precipitated in the state of 

 sulphuret of silver. 



If the current of chlorine be continued after the formation of 

 subbichloride of sulphur, an additional dose of it will combine 

 with the liquid, and if the process be continued long enough, the 

 whole will be converted into a chloride of sulphur, or a compound 

 of one atom chlorine + one atom sulphur. From an experiment 

 of Sir H. Davy, it would appear that this chloride may be formed 

 directly by putting sulphur into a sufficient quantity of chlotiiie 

 gas. ' 



3. Arsenic.-r—lihe. weight of an atom of arsenic, as I fixed it in 

 the last edition of my System of Chemistry, namely, 4-75, did 

 not accord veiy well with the atomic theory ; for it obliged us to 

 consider arsenious acid as a compound of 1 atom arsenic + 1-j. 

 atoms oxygen, and arsenic acid as a compound of 1 atom arsenic 

 + 2-^ atoms of oxygen. To get rid of these anomalies, it was 

 only necessary to double the weight of an atom of arsenic, and 

 to represent it by 9'5. We then have : 



Arsenic. Oxygen. 



Arsenious acid composed of 1 atom + 3 atoms 



Arsenic acid; . . , 1 +5 



I have shown in a paper published in the Annals of Philo- 

 sophy, xiv. 466, that the latest experiments of Berzelius (see 

 Annals of Philosophy, xv. 352) entirely agree with the composi- 

 tion of these acids as I had previously established .them, and 

 that he had laid aside his notions respecting their composition, 

 which he had founded on a set of hasty experiments. In another 

 'pa^ier {Annals of Philosophi/, xv. 81), I have given the analyses 

 of arseniates of potash and of soda, and shown that these salts, 

 when regularly crystallized, are neutral, and that the arseniate of 

 potash is a compound of 14'5 acid + 6 potash ; while the arse- 

 niate of soda is a compound of 14*5 acid + 4 soda. These salts, 

 therefore, correspond with the notion, that an atom of arsenic 

 weighs 9'5 ; an atom of arsenious acid, 12-5 ; and an atom of 

 arsenic acid, 14*5. It will be seen too from the same paper that 

 all the arseniates hitherto analyzed agree with the same thing. 

 I consider it, therefore, settled, that an atom of arsenic weighs 

 9-5. 



4. Tellurium. — Von Mons relates an experiment, said by him 

 to have been just made by Sir H. Davy, in Italy, upon what 

 authority I do not know ; but I shall give it to my readers as he 



