92 Dr. T. Thomson on PijroxyUc Spirit atid its Compounds. 



and the temperature becomes speedily liigh enough to allow 

 the process to go on without the further application of artifi- 

 cial heat. A very volatile liquid passes into the receiver, which 

 must be kept cool. This liquid is formate of methylene nearly 

 in a state of purity. 



To make it quite pure, it should be distilled first over a 

 fresh quantity of formate of soda, and afterward alone in a 

 dry retort over a water-bath. 



Pure formate of methylene thus obtained is very volatile, 

 lighter than water and has an agreeable aathereal smell. It 

 was analyzed by Dumas and Peligot by means of oxide of 

 copper, and found to be composed of 



Carbon 40*66 or 4 atoms = 3 or per cent. 40 

 Hydrogen 6*83 or 4 atoms = 0*5 — — 6*7 

 Oxygen 52-50 or 4 atoms = 4 — — 53*3 



100-00 7*5 1000 



Equivalent to C^ H^ O + C^ H O^ 



The specific gravity of vapour of formate of methylene, as 

 determined by Dumas and Peligot, is 2*084. Now 

 1 volume methylene vapour ... = 1*5772 

 1 volimie vapour of formic acid = 2*5672 



2)4*1644 



2-0822* 

 6. Benzoate of methylene. — This compound may be ob- 

 tained by distilling a mixture of 2 parts of benzoic acid, 2 

 parts of sulphuric acid, and 1 part of pyroxylic spirit, and 

 mixing the liquid which passes over into the receiver with 

 water. The aethereal portion separates. After washing it 

 two or three times with water, let it be agitated with chloride 

 of calcium, decanted off, and distilled over dry massicot. 

 Finally, let it be boiled till its point of ebullition becomes 

 fixed. It ought to be SS^°. 



Benzoate of methylene is oily, colourless, and has an agree- 

 able balsamic odour. Its specific gravity is 1*10 at 62|^°. It 

 is insoluble in water, but it dissolves readily in pyroxylic 

 spirit, alcohol, and aether. 



Its constituents, determined by the analysis of Dumas and 

 Peligot, are 



Carbon 71*4 or 16 atoms = 12 or per cent. 70*59 

 Hydrogen 6*2 or 8 atoms =1 — — 5*88 



Oxygen 22*4 or 4 atoms =4 — — 23*53 



1000 17 100*00 



* Ann, de Chim. ct dc Phijs,, Ixiii. 48. 



