244 



VINEGAR, CIDER, AND FRUIT-WINES. 



According to an older process, the pale brown salt is melted in 

 its water of crystallization, and then roasted in not too large 

 portions and with constant stirring in another boiler heated to 

 716 or 752 F., to destroy the remnants of tarry bodies. The 

 sodium salt will stand this temperature without being decom- 

 posed, but a few degrees above it, it will be decomposed and 

 charred so that only a mixture of sodium carbonate and coal re- 

 mains behind. The stirring which has to be kept up constantly 

 in order to prevent the temperature from getting too high in some 

 places, can be done by hand, but being laborious work it is better 

 to provide the boiler with a lid through the centre of which runs 

 a mechanical stirrer. When after roasting for 1 J hours the tar is 

 destroyed, the fused salt is thrown by means of an iron shovel 

 into water in a hemispherical iron boiler provided with a lid (Fig. 

 58). The salt is thrown into the gutter a, from which it runs 

 into the boiler b. The lid is necessary on account of explosions 

 which are unavoidable in throwing in the hot salt. 



Fig. 58. 



By dissolving the roasted acetate in water, the carbonaceous 

 portions remain undissolved ; the solution is, therefore, filtered 

 through linen bags c, and the filtrate collected in the pit d. If 

 necessary, the solution is further filtered through bone-black and 

 then evaporated to 24 B. By disturbing the crystallization 

 small crystals which are scarcely colored are obtained. This is 

 effected by the use of round copper crystallizing vessels with a 

 diameter of 5.72 feet, and a depth of about 10 inches (Fig. 59) 

 and the use of a mechanical stirrer. When crystallization is fin- 

 ished, the entire mass is brought into a copper boiler provided 

 with a large number of apertures about 0.11 inch in diameter, 



