1822.] Sixth Edition df his System of Chemistry. 269 



to which the Reviewer refers as the first which estabhshed the 

 true composition of sulphurous acid, I am not acquainted with 

 them. 



15. I may leave the Reviewer's remarks on my account of 

 arsenic to any reader of the least candour without being appre- 

 hensive as to the result. My statements in the System (as the 

 reader will find) were deductions from the experiments of Ber- 

 zehus, which I have since found not to be quite accurate. The 

 true atomic weights of arsenic and its compounds are given in 

 my paper in the Annals of Philosophy (New Series), vol. i. 

 p. 13; and vol. ii. p. 129. 



16. The Reviewer affirms that the analyses of Vauquelin, 

 Arvedson, and Gmelin, all concur to show that the weight of an 

 atom of lithia is 2*3, and that I, in defiance of these authorities, 

 make it 2*25. — (Review, p. 150.) I have shown in the very page 

 to which the Reviewer alludes, that the mean of the experiments 

 of Vauquelin and Arvedson give the weight 2*254, which very 

 nearly agrees with my number. 



17. The remark upon my directions for forming muriate of 

 barytes (Review, p. 150) shows that the Reviewer is not practi- 

 cally acquainted with the making of this salt. 1 have made it 

 very often, and have tried the Reviewer's method as well as 

 others. The directions in my System I think the best. Nothing 

 is gained by keeping out the iron of which the author speaks ; 

 because the muriatic acid of commerce is never free from that 

 metal. You must, therefore, heat your salt, and redissolve it in 

 water and crystallize, before you can get it in a state of purity, 

 whatever care you take to exclude the iron mixed with your 

 barytes. During the last two years I have generally prepared 

 the salts of barytes by fusing the sulphate with an alkaline car- 

 bonate, washing off the alkali, and then dissolving the carbon- 

 ate of barytes in the required acid. I am not sure that this 

 method is more economical than the other, but it is less trou* 

 blesome. 



18. The absurdities respecting manganese to which the 

 Reviewer alludes (p. 150) are absurdities of his own, not of 

 mine. I leave him to correct them at his leisure. As for my 

 account of steel, which he says has long been the ridicule of 

 practical men (p. 150), 1 have only to say that I have given the 

 best account of it which I could. I have witnessed the process 

 several times both in England and Scotland, and have availed 

 myself of the description of it published by Mr. Colher in the 

 fifth volume of the Manchester Memoirs. I must rest contented 

 in my ignorance till Mr. Brande thinks proper to enlighten the 

 world on the subject. 



19. The sneer against me (Review, p. 151) for not adopting 

 Mr. Donovan's estimate of the composition of the mercurial 

 oxides is quite misplaced. Wheji^4,.E^^\??^ <-¥-^' Donovan's 



noisniiqrao;) adi -^d 7. 



