60 Notices respecting New Books. 



" A crude vinegar has been long prepared for the cahco print- 

 ers, bv subjecting wood in iron retorts to a strong red heat. The 

 following arrangement of apparatus has been found to answer 

 well. A series of cast-iron cylinders, about 4 feet in diameter, 

 and 6 feet long, are built horizontally in brick work, so that the 

 flame of one furnace may play round about two cylinders. Both 

 ends project a little from the brick work. One of them has a disc 

 of cast-iron well fitted and firmly bolted to it, from the centre of 

 which disc an iron tube about 6 inches diameter proceeds, and 

 enters at a right angle the main tul)e of refrigeration. The dia- 

 meter of this tube may be from 9 to 14 inches, according to the 

 number of cylinders. The other end of the cylinder is called the 

 mouth of the retort. This is closed by a disc of iron, smeared 

 round its edge with clav-lute, and secured in its place by wedges. 

 The charge of wood for such a cylinder is about 8 cwt. Ti)e 

 hard woods, oak, ash, birch, and beech, are alone used. Fir 

 does not answer. The heat is kept up during the day-time, and 

 the furnace is allowed to cool during the night. Next morning 

 the door is opened, the charcoal removed, and a new charge of 

 wood is introduced. The average product of crude vinegar called 

 pyrolignous acid is 35 gallons. It is much contaminated with 

 tar; is of a deep brown colour ; and has a sp. gr. of 1.025. Its 

 total weight is therefore ai)out SOOlbs. But the residuary char- 

 coal is found to weigh no more than one-fifth of the wood em- 

 ployed. Hence nearly one-half of the ponderable matter of the 

 wood is dissipated in incondensa!)le gases. Count Rumford states, 

 that charcoal is equal in weight to more than 4-lOths of the wood 

 from which it is made. And M. Clement says that it is equal to 

 one-half. The Count's error seems to have arisen from the slight 

 heat of an oven to which his wood was exposed in a glass cylin- 

 der. The result now given is the experience of an eminent ma- 

 nufacturing chemist at Glasgow. The crude pyrolignous acid is 

 rectified by a second distillation in a copper still, in the body of 

 which about 20 gallons of viscid tarry matter are left from every 

 100. It has now become a transparent brown vinegar, having 

 a considerable empyreumatic smell, and a sp. gr. of 1.013. Its 

 acid powers are superior to those of the best household vinegar, 

 in the proportion of 3 to 2. By redistillation, saturation with 

 quick-time, evaporation of the liquid acetate to dryness, and 

 gentle torrefaction, the empvreumatic matter is so completely 

 dissipated, that on decomposing the calcareous salt by sulphuric 

 acid, a pure, perfectly colourless, and grateful vinegar rises in di- 

 stillation. Its strength will be proportional to the concentration 

 of the decomposing acid. 



The acetic acid of the chemist mny be prepared in the follow- 

 ing modes : 1st, Two parts of fused acetate of potash wilh one 



of 



