KNAPP'S CHEMICAL TECHNOLOGY. 28S 
Fig. 95. 
12,000 dollars; all the joints in the retorts are soldered 
with gold. During the boiling, the contents of the retort 
separate into commercial acid and some acid water, which 
is conducted by the tube in the capital, and its spiral leaden 
continuation to one of the pans, where it is used to concen- 
trate a quantity of weak acid from the chamber. If the 
heat were further increased, the boiling point would sud- 
denly rise to 326° C. (619 F.,) and hydrated sulphuric acid 
would distil over, which, of course, is not desirable. 
" With reference to the quantity of lead taken up by sul- 
phuric acid in different stales of concentration, experiments 
have lately been instituted by Anthon, which prove how 
very objectionable the practice must be of concentrating the 
acid in leaden pans beyond the prescribed limits. Anthon 
found in acid thus concentrated, and afterwards cooled 
