547 



February 13, 1845. 

 The MARQUIS OF NORTHAMPTON, President, in the Chair. 



'Afj.6p(j)(0Ta, No. 1. "On a case of Superficial Colour presented 

 by a Homogeneous Liquid internally colourless." By Sir John Fre- 

 derick William Herschel, Bart., F.R.S., &c. 



The author observed that a solution of sulphate of quinine in tar- 

 taric acid, largely diluted, although perfectly transparent and colour- 

 less when held iDetween the eye and the light, or a white object, 

 yet exhibits in certain aspects, and under certain incidences of the 

 light, an extremely vivid and beautiful celestial blue colour, appa- 

 rently resulting from the action of the strata which the light first pe- 

 netrates on entering the liquid ; and which, if not strictly superficial, 

 at least exert their peculiar power of analysing the incident rays, and 

 dispersing those producing the observed tint, only through a very 

 small depth within the medium. The thinnest film of the liquid 

 seems quite as effective in producing this superficial colour as a con- 

 siderable thickness. 



February 20, 1845. 

 The MARQUIS OF NORTHAMPTON, President, in the Chair. 



" Additional Remarks respecting the Condensation of Gases." By 

 Michael Faraday, Esq,, F.R.S. &c. 



The author, suspecting the presence of nitrogen in the nitrous 

 oxide on which he had operated, repeated his experiments with this 

 gas, very carefully prepared from pure nitrate of ammonia, but the 

 results still indicated the presence of a more volatile gas mixed with 

 another less volatile. He found that olefiant gas is readily soluble 

 in strong alcohol, sether, oil of turpentine, and other bodies of the 

 same kind ; and that, like the former gas, it seems to be of a com- 

 pound nature. His experiments confirm the prevalence of the law 

 that the force of vapour increases in a geometrical ratio for equal 

 increments of heat, commencing at a given amount of pressure. The 

 more volatile a body is, the more rapidly does the force of its vapour 

 increase by an augmentation of temperature, the increase of elasti- 

 city being directly as the volatility of the substance. By further and. 

 more accurate investigation, a general law may be established for 

 deducing, from only a single observation of the force of any given 

 vapour in contact with its fluid, its elasticity at any other tempera- 

 ture. 



Postscript to the Paper by Sir John F. W. Herschel, Bart., F.R.S., 

 read at the last meeting. 



The author found that neither cinchonine nor salicine, in a state 

 of great purity, possessed, in the smallest appreciable degree, the 

 optical property which he has shown to belong to quinine. 



