438 REPORTS ON THE STATE OP SCIENCE. 



nmongst the ammonio-metallic compounds (chlorides and nitrates of the 

 roseopentamine bases) — where the compounds MX 3 ,5NH,,IL,0 are 

 much more soluble than the corresponding anhydrous salts MX 3 ,~5NH 3 . 



He also made mention of the fact that organic anhydrides, lactones, 

 oxides, &c, are less soluble than the hydrated compounds. 



Other instances of the chemical constitution of a substance 



influencing its solubility may be seen from a comparison of the solubility 



1094 °f the calcium, barium, and silver salts of the fatty acids. In this 



connection Lichen 220 found certain fixed relations between the 



constitution of the acids and the solubility of their salts. 



For the normal acids the relationship is simple; each substitution 

 of a methyl group for hydrogen producing a regular change in the 

 solubility of the salt. In the cases of acids other than normal, although 

 undoubtedly existing, the connection between constitution and solubility 

 is not evident. 



i on* From a study of the solubility of various benzene derivatives 



in water, Vaubcl 233 concluded the solubility of these substances 

 is primarily conditioned by the presence of an amido-, hydroxyl-, or 

 carboxyl- group. He also observed that the dissolution tendency of 

 these groups is weakened by such substituents as the methyl, bromine, 

 iodine, or nitro groups. 



In the case of isomeric derivatives the meia- substituted compound 

 has greatest and the para- substituted compound the least solubility. 

 Carnelley and Thomson's rule that for isomeric organic compounds the 

 order of solubility is the same as the order of fusibility does not hold. 



V. A (i) — Solubility in relation to Temperature. 



The fact that change of temperature influenced the solubility of most 

 substances was an early discovery, but probably the first accurate study 

 of this phenomenon is to be found in a memoir by Gay-Lussac* 

 To this worker is also to be attributed the formula expressing the 

 solubility of salts where the increase of solubility is proportional to the 

 temperature. In those cases where this proportionality did not exist 

 _ , n Kopp 10 arrived at a mathematical expression connecting solubility 

 and temperature. He also extended his work to cases where the 

 solubility of a salt was influenced by the presence of another salt, with 

 like base, and also with like acid — namely, KN0 3 with K,S0 4 , &c, and 

 KC1 with BaCl 2 , &c. This was followed by an extensive investigation 

 by Poggiale, 12 who determined the solubility of sixteen salts at 

 intervals of 10° 0. ; from his results, however, no general con- 

 clusion could be drawn. 



r BunSen 19 studied the absorption of gases in liquids, and in- 



°°' troduced the term ' absorption coefficient ' as indicating the volume 

 of gas, reduced to 0° and 760 mm., which is absorbed by unit volume 

 of a liquid at normal temperature and pressure. He showed the 

 absorption coefficient was independent of pressure, but (except in some 

 cases, as hydrogen, oxygen, and carbon dioxide) depends upon tempera- 

 ture and the nature of the gas.* 



* This work was carried further by Carius, who studied the absorption of 



