266 
MANUFACTURE OF ACETIC ACID. 
steam or manual power. When the mixture is complete the door 
is opened, and the contents of the cylinder discharged into a tub 
or other vessel placed underneath the front of the cylinder. The 
pulpy mass is next transferred to shallow iron trays two feet wide 
and from two to four feet feet in length, and two inches deep. 
These are placed in cast-iron cylinders about five feet long and 
three feet wide, and each layer of trays is separated, the one 
from the other, by means of iron rods placed between them ; the cy- 
linders are exposed to the direct action of the fire, and the acetic 
acid passes off in the form of vapor, which is condensed by pass- 
ing it through leaden worms immersed in cold water. 
This impure acid, which is contaminated with sulphurous acid and 
free sulphur, produced by the re-action of the tarry matter of the 
acetate of lime or the excess of sulphuric acid, is then run into 
leaden vessels, placed in an iron cylinder and submitted to distilla- 
tion. The liquid product is condensed by passing it through an 
earthenware worm. The acid in this state is employed in the man- 
ufacture of sugar of lead. Fifteen cwt. of brown acetate of lime, 
with seventy-five per cent, of sulphuric acid of specific gravity 
1.770, and ten gallons of water, produce about 1500 pounds of 
rough acid of specific gravity 1.070. Sometimes a larger quan- 
tity of water is employed. On a small scale the following results 
were obtained : — 
Acetate of Lime. Sulphuric Acid. Water. Acptic Acid Specific gravity, 
lbs. lbs. lbs. lbs. 
12 Grey .. 9 .... 15 produced 21J . 1.056 
12 " . . 9 . . . 10 " 17 . 1.073 
12 Brown . . 9 . . 15 " 18 . 1.050 
On the large scale, one ton and a half of rough acetic acid, of 
specific gravity 1.050, should be obtained from one ton of good 
acetate of lime, and three quarters of a ton of sulphuric acid. 
Acetate of lime may be so prepared, and the decomposition and 
rectifying processes so carried on, that the acid obtained is not 
readily distinguishable from that obtained from acetate of soda. 
At some work copper stills, set over the naked fire are employ- 
ed, and the acid is redistilled in copper stills, set in a sand heat. 
Iron stills of various sizes, with a flat cover, formed of magnesian 
lime stone, or of rough burnt clay, or of metallic tin, are also used. 
Large stills are not desirable, because towards the end of the dis- 
