^0. 3.] CHEMISTRY. 183 



silk of a fine red colour ; and that by giving* the worms lettuce- 

 leaves, they have produced cocoons of an emerald-green colour, 

 -M. DelidoB de St. Grilles, of Vendee, has also, by feeding silk- 

 worms — duritsg the last twenty days of the larva period — on vine, 

 lettuce, and nettle-leaves, obtained green, yellow, and violet 

 tcocoous. — Afhenceum. 



A collection of freshwater fishes, made at Shanghai by H.M. 



Consul, Mr. E. Swiuhoe, has been reported on by Dr. A. Giinther, 



of the British Museum. The collection is notable for containing 



an. unusually large proportion of new species, or such as have 



:liitherto been but imperfectly known. — Ibid. 



CHEMISTRY. 



Synthesis of Marsh Gas and Formic Acid. — Sir B. C. 

 Brodie has found that if a mixture of hydrogen and carbon oxide 

 is submitted to the action of electricity in the induction tube, a 

 contraction of volume ensues accompanied with the production 

 of marsh-gas. The reaction is expressed by the equation — 



CO + 3H2 = C4 + H2O. 

 It was also found that on treatins: a mixture of carbon diox- 

 ide and hydrogen in a similar manner, the resultant gas contained 

 carbon oxide, while minute drops of an oily liquid collected in 

 the tube. These gave the characteristic reactions of formic acid, 

 and their production may be represented by the equation — 



H2 + CO2 = H2 CO2 



Note on Silicic Acid. — C. Rammelsberg has found that 

 silica which after a short ignition, dissolves in a holing solution 

 of potassium or sodium carbonate, loses this property, either 

 partly or almost entirely, when it is subjected to a more pro- 

 longed and stronger ignition. Hence when the silica obtained 

 in analysis is to be dissolved in potassium or sodium carbonate; 

 this operation should be performed before its ignition. 



The author has made a series of determinations of the water 

 -contained in silica obtained by the decomposition of an alkaline 

 silicate, or of Wollastonite, and finds that this substance, when 

 dried over oil of vitrol, contains 4*5 to 7 per cent of water, and 

 -that when it is dried at 100® to 140°, it retains from 4 to 5*7 



