Improvements in Science. 443 



the atmospheric pressure causes to enter the flask. He 

 affirms, that the lead takes up all the oxygen from the air 

 which undergoes a diminution of volume of 21-05; but as 

 lead absorbs carbonic acid also, amounting, in his experi- 

 ments, to -0004 ; it follows, that the quantity of oxygen 

 in the atmosphere is 21*01 per cent. Gay Lussac has 

 suggested another eudiometer, viz., a plate of copper 

 moistened with sulphuric, muriatic or acetic acids.* 



Molecular composition of bodies. — Persoz, in a paper read 

 before the Institute, has come to the following conclusions 

 on this subject, 1. Chemical atoms are only molecular 

 groups, the relative value of which is expressed by the 

 atomic weight. 2. These groups are all divisible by a 

 constant number (70), which expresses the volume of 

 vapour, that the atomic weight of a body furnishes. 3. If 

 we multiply this number (70) by a factor corresponding to 

 the volumes of a molecular group, and take the product 

 as the divisor of the relative weight of this group, the 

 quotient will be the weight of a litre of the vapour, by means 

 of which we may deduce at pleasure (taking into account 

 only the molecular change which supervenes in its passage 

 from the solid to the gaseous state) the density of a body 

 compared to that of air or water. 4. The density being 

 intimately connected with the relative weight of the atoms, 

 we can, by means of the specific gravity of a body, verify 

 the analytical results obtained by chemists. 5. By a 

 knowledge of the density, we may establish the molecular 

 composition of bodies, and distinguish that of certain 

 gases with the composition of the molecular groups which 

 produces them. This would lead to the knowledge of the 

 laws of the dilitation of gases. 



We are glad to find, that important views like these, 

 which, in many respects, are just those advocated in the 

 pages of this Journal, and previously in the " First Prin- 

 ciples," are beginning to attract attention in France.-f- 



Solubility of some Carbonates, ^c. in Sal Ammoniac. — 

 According to Vogel, carbonate of lime, when newly pre- 

 cipitated, Iceland spar, white marble, carbonates of barytes 

 and strontian, precipitated from these solutions, and also 

 witherite are all soluble in sal ammoniac. Hence, a sub- 



• Ann. de Cbim. Ixii. 219. t L'Institut, 181. 



VOL. IV. 2 G 



