TRANSACTIONS OF SECTION B, 591 



5. On the Colour of the Oxides of Cerium and its Atomic Weight.^ 

 By H. Robinson, M.A. 



This paper was principally a criticism of Wolf's paper on the atomic weight of 

 cerium, puhlished iu the 'American Journal of Science and Art/ 1868. Great 

 prominence is given to this work in Clarke's ' Constants of Nature.' Wolf's eerie 

 oxide was white, and the atomic weight of the metal was 137 •, or, as recalculated 

 by Clarke, 138'. The writer of the present paper contended that Wolf's method 

 of separation was wrong — tliat it would not give eerie but lanthanum oxide, which 

 is white, and which contains a metal with an atomic weight lower than that of 

 cerium. Wolf's method of separation was repeated fractionation of impure cerous 

 sulphate by gentle evaporation. Robinson made similar experiments and found 

 the proportion of Ce^Oj to LajOg decreased from 4 to 1 to 2 to 1 by making the 

 same number of crystallisations Wolf had done. He also found that at the 

 temperature of the evaporation, 65°, 100' cc. of water held in solution 10'296 

 grains of Oe._,3SO^, wliile under the same conditions onl}' 2"106 grains of La23SO^ 

 remained in solution in the same quantity of water. He maintained the colour of 

 eerie oxide is not white, as is sometimes supposed, but a pale sulphur yellow, and 

 that the atomic w^eight of cerium is 140"2, as found by himself and also by 

 Branner. 



6. On the Determination of the Constitution of Carhon Compounds from 

 Thermo-chemical Data. By Professor Aemstbong, F.B.S, 



7. On the relative Stability of the Cam2)hene Hydrochlorides C^oH^yCl ob- 

 tained from Turpentine and Camphene respectively. By Ernest F. 

 Ehrhakdt.^ 



Riban has shown that the former of these bodies is less easily decomposed by 

 water ; the author shows that it is also more stable under the influence of heat. 

 Tilden has shown that at a low red heat turpentine breaks up more completely 

 than campheue ; the author extends this observation to lower temperatures, by 

 observing the vapour densities in a bath containing melted lead. 



The paradoxical result that the hydrochloride from the stable hydrocarbon is 

 less stable than that from the unstable one is held to prove that this is a ' molecular ' 

 compound, the chlorine in it remaining associated with the hydrogen of the acid, 

 while at the same time being attached to the hydrocarbon. 



8. On Derivatives of Tolidin and the Azotolidin Dyes. 

 By R. F. RuTTAN, B.A., M.D. 



Tolidin and its older homologue benzidin have only quite recently become 

 prominent, owing to the discovery of the so-called azo-colours. 



Benzidin was first prepared by Zinin, in 1845,^ and its mode of formation from 

 hydrazobenzene described by Hafman •* Schultz * established the now accepted 

 formula for this base, and investigated many of its reactions. Tolidin was 

 prepared in an analogous way to benzidin, but its reactions were not studied. 

 Petriew,^ who was the first to obtain orthotolidin, only in small quantity, however, 

 gives the melting-point 112°. This is too low ; the proper melting-point is 127-128°. 

 Generally this base resembles benzidin very closely in its behaviour, but diflers 

 considerably from toluidine. 



It forms with mineral acids two series of salts, the acid salts being the more in- 

 soluble. It gives a play of colours from green to blue, finally scarlet, on dropping 



• Published in extenso in the Chemical News, vol. liv. p. 229. 

 - Chemical News, November 13, 1886. 



' Journal fiir 2)ractische Cheviie, xxxvi. p. 93. ^ Jakreshcriehte, 1863, p. 424, 



* Luby's Annialen, p. 174. « Berichte, vi. p. 557, 



