284 
KNAPP'S CHEMICAL TECHNOLOGY. 
down to 6S° F., the following quantities of sulphate of 
lead : 
"Acid sp.gr. 1.724 contained ^-^o^hs of sulphate of lead. 
u u 1.791 u u u 
" 1.805 " iT^o^^s " " 
The annexed wood cut (fig. 96) shows the manner in which 
the platinum still is erected in the concentrating house of 
the vitriol works. 
" The high price of platinum vessels renders it very much 
to the interest of the manufacturer that they should be in 
constant use ; yet it is impossible to draw off so powerful 
an acid at that temperature into the glass carboys in which 
it is sent out, and leaden coolers cannot be used. Hence 
arises the necessity of the platinum syphons, figs, 97 and 98, 
