428 Mr. Prideaux's Continuation of the Table of AtomicWeiglits, 



(a.) Acetic, Succinic, &c. — The slight augmentation in the 

 decimal is required for the increased estimate of the atom of 

 carbon. 



(b.) Antimonic. — Thomson's number is adopted for the 

 simplicity of its relation to bases, in connection with the con- 

 siderations in the note on antimony (ubi supra), but with the 

 qualification there stated. 



(c.) Arsenious, Arsenic. — It is difficult to read the account 

 of Berzelius's investigations (Ann. Phil. xv. 352.) without feel- 

 ing convinced by them. Those of Thomson (First Principles, 

 i. 229) are almost equally convincing ; yet both cannot be 

 right. The sulphurets of arsenic appear, in Berzelius's paper, 

 to consist respectively of As S a and As S', analogous to 

 Thomson's constitution of the acids ; which, having also the 

 advantage of simplicity, in relation both to the bases with 

 which they combine, and the oxygen they contain, seems 

 rather entitled to preference. 



(d.) Benzoic. — If carbon be 0*76, benzoic acid will be 15*] 5. 

 But the mean between Thomson's and Berzelius's number for 

 carbon is a fraction below 0*76, whence the number adopted. 



(e.) Boracic. — See the note on Boron. 



(f.) Perchloric. — Berzelius's reasons for giving this acid 

 a different constitution from that assigned by its discoverer 

 (First Princ. i. 85) not appearing, the latter is adopted. 



(g.) Chloriodic, &c. — Calculated from the components in 

 the former table. 



(//.) Citric. — About the composition of crystallized citric 

 acid there is some obscurity; which, though of little import- 

 ance in chemistry, is otherwise in extemporaneous pharmacy, 

 iu which its neutralization is a frequent desideratum. 



The most satisfactory analyses of it are those of Berzelius 

 (Ann. Phil. v. 93.), and of Prout (Phil. Mag. and Annals, hi. 

 109), which nearly coincide: the former giving the crystals 

 17 per cent of water; the other resolving them into 



Carbon 6 atoms. 



Oxygen 3 atoms. 



Water 5 atoms. 



Chemists are generally agreed in making the dry acid con- 

 sist of 4 atoms of carbon, 4 atoms of oxygen, and 2 atoms of 

 hydrogen : hence Dr. Prout's statement gives 2 atoms of water 

 to 1^ acid; which is confirmed by Berzelius's table (Essai), 

 as well as by the quantity of water above stated. But 3 atoms 

 of acid to 4 of water is so strange a combination, as not 

 easily to obtain our acquiescence. The equivalent weight 



would turn out Acid 1 7*27 



Water l£ 1-5 



8-77 



Thomson 



