97 
smaller tube is by means of the blowpipe perforated at the 
bottom with a quarter-inch hole and is also provided with a 
rubber stopper and a gas leading tube bent twice at right 
angles. The larger tube has a piece of rubber tube two 
inches in length, and of rather smaller diameter than itself, 
pushed over its mouth, one inch on the tube and one inch 
projecting. This completes the apparatus. To work it fill 
the larger tube from one third to one half full of a mixture 
of sulphuric acid and water — one part acid, three parts 
water. Drop a lump of iron sulphide into the smaller tube, 
insert the stopper with leading pipe firmly into this, and 
thrust its lower perforated end through the rubber mouth 
of the larger tube, pushing it down until it reaches the acid ? 
and allowing sufficient of this to enter the perforation to 
cover the sulphide iron. Gas immediately commences to 
be evolved and can be bubbled through the solution to be 
examined. When sufficient has been obtained, raise the 
upper tube until the lower end is out of the acid, the 
remains of which at once drain away from the sulphide and 
all action ceases, or practically so. It is only necessary to 
hang up the apparatus until again needed, when, by heating 
the end of the lower tube containing the acid over a Bun- 
sen burner, and pushing down the upper, it commences full 
action again. This can be repeated until the acid becomes 
saturated, or so mucli so as to require replenishing. 
Of course it need not be limited to the dimensions I have 
named. A much larger upper tube might be employed, 
which, combined with a suitably sized lower bottler would 
furnish gas enough for a quantitative analysis. By 
occasionally sinking the upper tube deeper into the acid the 
stream may be fairly regulated, sufficiently so at all events 
for ordinary work. 
