6S M. Liebig on a new Method for Silvering Glass, 



large quantity of a new body, having the greatest similarity 

 with leucine, both in appearance and chemical relation. It 

 is homologous, and not identical with leucine. Its formula 

 is C'o H»» NO*; that of leucine is C^^ hi3 ^q4 tj^^ Qt^er 

 conclusions he has arrived at have merely a special physiolo- 

 gical interest. 



Carius describes a compound of sesquioxide of manganese and 

 sulphuric acid. It is obtained by headng binoxide of manga- 

 nese with concentrated sulphuric acid. The excess of sulphuric 

 acid is removed by washing with strong nitric acid, as the sub- 

 stance is decomposed by water, and the nitric acid is afterwards 

 expelled by a gentle heat. It has the formula Mn^ 0^, 3S0^. 

 It forms a deep green powder, without a trace of crystallization ; 

 attracts moisture with great avidity, and must be kept in closed 

 tubes. By treatment with water it is converted into hydrated 

 oxide of manganese, and is indeed the best source for this 

 body. 



The Para nuts, the produce of a tree, the Bertholletia excelsa, 

 which belongs to the family of the Lecythodece, contain upwards 

 of 50 per cent, of a fatty oil. This oil, according to an inves- 

 tigation of Caldwell, consists of stearine, palmitine, and oleine. 



According to Grimm and Ramdohr, the gas produced by the 

 action of sulphuric acid on ferrocyanide of potassium is not pure 

 carbonic oxide, but contains 11 per cent, of sulphurous acid. 

 This appears to be reduced from the sulphuric acid by some 

 of the carbon in the ferrocyanide. 



Liebig gives a new method for silvering glass in the cold, 

 which answers its purpose extremely well. The silvering liquid 

 consists of an ammoniacal solution of nitrate of silver, contain- 

 ing caustic soda or potash. Before using, this is mixed with 

 one-eighth or one-tenth of its quantity of a solution of sugar of 

 milk, containing one part of sugar of milk to ten parts of water ; 

 the glass plates to be silvered are then dipped into this mixture, 

 and allowed to remain in about a quarter of an hour ; the silver- 

 ing is then complete. The process is not costly ; a square metre 

 of surface requires silver of the value of 5d, Liebig goes into 

 the details necessary for ensuring success. 



Glass can only be permanently gilded with the aid of heat. 

 The gilding liquid is composed of a solution of double chloride 

 of gold and sodium, containing some caustic soda. At the 

 time of using, alcohol and sether are added to it, and a gentle 

 heat applied. As in the former case, certain precautions arc 

 necessary, for which we must refer to the original paper. 



