Progress of Invention. 227 



PROGRESS OF INVENTION. 



Production of Formic Acid for Industrial Purposes. — The use 

 of this important acid has been more or less limited hitherto, by the 

 difficulty, and consequent cost, of its production. The mode of 

 obtaining it devised by M. Lorin leaves notbing to be desired, 

 either with regard to simplicity or cheapness. His process is 

 founded on the power which glycerine possesses of producing 

 formic acid by the decomposition of oxalic acid ; but he applies the 

 principle in such a way as to obtain directly formic acid of great 

 strength. He heats a mixture of ordinary oxalic acid and an- 

 hydrous glycerine ; reaction begins at 79° Cent., and attains a 

 maximum at 90° ; carbonic acid is disengaged, and an aqueous fluid 

 charged with formic acid passes over. Adding a new quantity of 

 oxalic acid to the glycerine, some time after the evolution of 

 carbonic acid has ceased, causes decomposition to recommence, and 

 a fluid still richer in formic acid passes over. Successive additions 

 of oxalic acid to the glycerine at length causes the formic acid in 

 the receiver to be of the strength required for crystallization. The 

 process is very simple ; and as the evolution of carbonic acid marks 

 its phases sufficiently, it is unnecessary to pay any attention to the 

 temperature. The same glycerine might be used for the production 

 of any amount of the acid, except that the impurities always found 

 in the oxalic acid would lead to waste. The same glycerine has, 

 however, been used continuously night and day for months. The 

 process just described affords a product containing 56 per cent, 

 formic acid; if anhydrous oxalic acid is used, the product will 

 contain 75 per cent. acid. Decomposition will commence at 50° 

 Cent. ; and care must be taken to apply the heat cautiously, so as 

 to prevent an inconvenient swelling up of the mass. Monohydrated 

 crystallizable formic acid may be obtained by acting on formic acid 

 of 70 per cent., at an elevated temperature, with anhydrous oxalic 

 acid, and distilling. It crystallizes when the temperature is lowered 

 sufficiently. 



Formic Ether. — The process just described supplies a means of 

 producing formic ether, a fluid having a remarkably agreeable 

 odour, with great economy. Oxalic acid and alcohol, in nearly 

 equivalent proportions, corresponding to the ether required, are 

 added, at the same time, to saturated glycerine, and submitted to 

 the proper temperature. The formic acid, according as it is pro- 

 duced, combines in the nascent state with the alcohol. The con- 

 densed vapours are to be returned to the retort when the decom- 

 position of the oxalic acid is complete, and the ether is to be 

 distilled over : it may be purified in the usual manner. 



Silk Producible in these Countries. — Hitherto the economic 

 production of silk has been confined to hot countries ; the Acclima- 

 tization Society of Paris has, however, recently introduced a silk- 

 worm (JBomhyx Cynthia) which will thrive well even in northern 

 climates, being unaffected by rain, wind, or frost ; the only effect, 

 indeed, produced by the genial nature of the climate being the more 



