MANUFACTURE OF ACETIC ACID. 
265 
for the next operation. A silver arm to connect the head with the 
earthenware worm is sometimes used, a regular supply of cold 
water being kept dripping on the metallic arm. The residuum 
left in the still after the distillation of the acid, is sulphate of soda, 
which should be in the state of an almost dry crystalline powder, 
when the process has been well conducted : this may be dissolved 
in water, and the solution filtered, evaporated, and crystallized ; or 
it may be used in the manufacture of acetate of soda. 
Manufacture of Glacial Acetic Acid. — Acetic acid may be obtained 
in a glacial state by using dry acetate of soda from which the 
water of crystallization has been expelled by heat; to this is added 
about its own weight of strong oil of vitriol, specific gravity 1.85. 
The first three-fifths of the product should be collected separately, 
the last, two-fifths will crystallize. 
Manufacture of Acetic Acid by the Decomposition of Acetate of 
Lime by means of Sulphuric Acid. — Large quantities of this acid 
are employed in the manufacture of acetate of lead and other com- 
mercial acetates, white lead, and emerald green ; also in the pre- 
paration of the inferior class of pickles, &c. &c. Much of the 
rough acid is sent from Wales to London, and purified by re-distil- 
lation. The rough acid is obtained in Wales and other parts of 
the country in the following manner : — A cast-iron cylinder, about 
four feet long and two feet wide, closed at one end, is fitted with 
an iron rod passing through its interior, and furnished with nume- 
rous projecting pieces of iron, which reach almost from the center 
rod to the inner sides of the cylinder. The other end of the cylin- 
der is screwed on so as to be readily removed at any time when 
the cylinder is to be cleaned or repaired. This end is divided into 
two parts, one of which, occupying a space of about two-thirds of 
the whole, is fixed on the upper part, the other one-third is occu- 
pied by a moveable door, closing an aperture through which the 
contents of the cylinder may be removed; through this upper part 
one end of the iron rod above-mentioned passes, and is attached to 
a handle, by means of which a rotatory motion is communicated to 
the rod and its appendages, and the contents of the cylinder are 
kept in continual agitation. This vessel is termed an agitator. It 
is placed in a horizontal position on a mass of brickwork or ma- 
sonry. At its upper part is an opening, through which the acetate of 
lime, sulphuric acid and water is passed ; motion is given either by 
