Chemical Science. 409 



15. New Animal Soap. — M. GeofFroy de Villeneuve has lately 

 transmitted a quantity of a peculiar kind of soap, from Africa 

 to Paris, with the following note : — " Being in the village of 

 Postudal, a few leagues from Senegal, employed in collecting- 

 insects, and inviting the negroes to procure me supplies, one 

 of them presented me with a pot containing many thousands 

 of a small insect of the carab genus. They were ready dried, 

 and the numbers shewed that they had been collected for some 

 particular purpose. On inquiring, I learned that this insect 

 entered into the composition of the soap used in the country ; 

 the same negro also shewed me a ball of this soap, which was 

 of a blackish colour, but had all the properties of our common 

 soap ; and I learned, in the sequel, that these insects are con- 

 verted to the same purpose all along the coast of Senegal. This 

 carab is black, but the edges or borders of the corselet, and 

 also the elytres, are of a reddish colour ; the feet and the an- 

 tennae, of a pale colour." 



16. Oxalate of Potash and Manganese. — When the black 

 oxide of manganese and the super-oxalate of potash are tritu- 

 rated together, and moistened, there is considerable efferves- 

 cence occasioned by the formation of carbonic acid gas ; and if 

 more water be added, and the whole filtered, a red solution of 

 an admirable colour is obtained. This solution is neutral, and 

 is a triple oxalate of potash and deutoxide of manganese. If, 

 however, it be left some time, it loses colour ; the manganese 

 takes the state of protoxide, and a colourless triple salt is ob- 

 tained. We are indebted to M. Van Mons for the knowledge 

 of this interesting decomposition. 



17. Platinum Leaf. — Platinum is now prepared, in Paris, in 

 leaves as thin as those of leaf gold. 



18. Evolution of Heat bij Freezinr/. — M. de la Beche has de- 

 vised an ingenious way of shewing the heat evolved by water 

 during congelation. He places a glass vessel, containing in 

 lis lower part water, and upon that olive oil, in a temperature 



