Intelligence and Miscellaneous Articles. 409 



tate of potash, and the mixture is distilled, part of the valeric acid 

 distils, while in the residue there is a mixture of acid acetate of pot- 

 ash and valerate of potash. 



When a mixture of acid acetate of potash and valeric acid is di- 

 stilled, this acid distils and the acid acetate of potash remains free 

 from valeric acid ; butyric acid acts similarly to valeric acid with 

 acetate of potash. 



It results from what has now been stated, that when butyric or 

 valeric acid, containing acetic acid, is partially saturated with potash, 

 one of two things happens : either the acetic acid remains entirely 

 in the residue with a certain quantity of butyric acid, and then the 

 acid which distils is free from acetic acid ; or the residue is formed 

 entirely of acetic acid, and then the product of the distillation still 

 contains acetic acid, which may be separated from the butyric acid 

 or from the valeric acid by a second similar treatment. — Journ. de 

 Pharm. et de Chim., Mars 1850. 



ON THE COMPOSITION OF THE PRECIPITATE FORMED IN SO- 

 LUBLE CYANIDES BY SUBACETATE OF LEAD. BY M. E. ER- 

 LENMEYER. 



When hydrocyanic acid is added to subacetate of lead, no preci- 

 pitate is formed ; ammonia is requisite to produce it, by which a pul- 

 verulent white precipitate is formed and readily deposited. 



In order to analyse it, M. Erlenmeyer washed it with water free 

 from carbonic acid, collected it on a filter, and dried it on watch- 

 glasses under a receiver containing lime and sulphuric acid. During 

 drying the precipitate gradually changes from white to yellowish- 

 white, and continually evolves hydrocyanic acid. When dry the 

 decomposition ceases ; it consists, according to the author, of 2PbO, 

 PbCy. 



Its composition is the same whether aqueous or alcoholic solutions 

 of ammonia or potash be employed in preparing it. The author 

 adds, that it appears probable that the white precipitate is at first 

 cj'anide of lead, which is gradually decomposed by water into hydro- 

 cyanic acid and oxide of lead ; the decomposition would stop when the 

 composition of the substance is that indicated by the above formula. 

 —Ibid. 



THEORY OF COMPLEMENTARY COLOURS. BY M. MAUMEN^. 



The author has described, in a letter to the Academy of Sciences, 

 an experiment which is interesting as regards the demonstratioii' of 

 the theory of complementary colours. 



It is well known that the combination of two complementary 

 colours produces white ; and this is usually shown in lectures by 

 employing two glasses, one of a red and the other of a green colour, 

 the tints of which, although of considerable intensity, entirely dis- 

 appear during the simultaneous interposition of the glasses between 

 the eye and the source of light. M. Maumene several years since 



