186 PEOFESSOR THOMAS GRAHAM's SCIENTIFIC WORK. 



ume, of turpeiitiue vapor, iu air under ordinary pressure, rendered it 

 incapable of effecting tlie slow oxidation of phosphorus. He also ob- 

 served and recorded the influence upon the oxidation of phosphorus of 

 various additions of gas and vapor to air, under different circumstances 

 of pressure and temperature. 



II. 



Hydration of compounds.— In the earliest of Mr. Graham's published 

 memoirs, that '• On the absorption of gases by liquids,"* he contended 

 that the dissolution of gases in water, at any rate of the more soluble 

 gases, is a chemical phenomenon, depending on their essential property 

 of liquefiability being brought into play by their reaction with the sol- 

 vent, that is to say by their hydration. The results of some further 

 work on the same subject he published under the title of " Experiments 

 on the absorption of vapors by liquids." t 



In 1827 he gave to the Eoy.al Society of Edinburgh "An account of the 

 formation of alcoholates, definite compounds of salts and alcohol analo- 

 gous to the hydrates."! In this paper, after a description of some ex- 

 periments on the desiccation of alcohol, he showed that anhydrous 

 chloride of caicium, nitrate of lime, nitrate of magnesia, chloride of zinc, 

 and chloride of manganese have the property of uniting with alcohol, as 

 with water, to form definite compounds. The crystalline compound with 

 choride of zinc, for instance, containing 15 per cent, of alcohol, he rep- 

 resented by the formula Zn CI . 2 C2H3O; corresponding to the modern 

 formula Zn Cl2.2C2HeO. 



In 1835 Mr. Graham communicated a paper, also to the Eoyal Society 

 of Edinburgh, " On water as a constituent of salts." § In this paper he 

 showed more particularly that the so-called magnesian suli)hates, crys- 

 tallizing usually with 7, 6, or 5 proportions of water, gave up all but the 

 last proportion of water at a moderate heat, but retained this last propor- 

 tion with, great tenacity. The comparatively stable mono-hy drated salts, 

 mono-hydrated sulphate of zinc, for instance, Zn O . S O3. U O, he re- 

 garded as the analogues of crystallizable sulphuric acid II O . S O3 . H O. 

 lie showed further that the firndy retained water of sulphate of zinc, 

 for instance, differed from the firmly retained water of phosphate of 

 soda, in not being basic, or replaceable, that is to say, by metallic oxide. 

 He conceived, however, that in the double sulphates, potassio-sulphate 

 of zinc, for instance, Zn O . S O 3, K O . S O 3, the water of the compound, 

 ZnO. SO3.H O, was replaced by alkali-sulphate, and he accordingly 

 designated the water of this last, and of similar compounds, by the name 

 of saline or constitutional water. 



In the following year, 1836, Mr. Graham communicated to the Koyal 



* Thomson, Annals of Philosoiiby, xii, 1826, p. 69. 



t Edinburgh Journal of Science, viii, 1828, p. 326. 



t Edinburgh Royal Society Transactions, xi, 1837, p. 175. 



^S Ibid., xiii, 1836, p. 297. 



