auxiliary tank or generator (B) in which the gas is generated. The pipe leading from the fourth opening to the auxiliary or generator is provided with a gas cock and three enlargements, 4a, 4b, and 4c (the latter is not shown in the photograph). Two of these enlargements contain sodium cyanide, and the third glass wool. The object of the sodium cyanide and glass wool is to pick up any free sulphuric acid which may be mechanically drawn from the generator when the gas is permitted to enter the fumigation chamber. The auxiliary or generator (B) is so arranged that it can be used as a generating tank or as a fumigating chamber, by closing the gas cock just above the cylinder. The exhaust pipe which leads from the generator to the small vacuum pump (D) is shown as figure 9. No. 5 is a tubulature used in introducing the chemicals into the generator. No. 8 is a pipe which carries water to cool the air pump (C), and No. 10 is the cooling pipe for the small air pump (D). No. 11 is the pipe which carries the exhaust from the small air pump, and No. 6 is a combination pressure and vacuum gauge. No. 7 is a rheostat. The material to be fumigated is placed in the retort (A), the door closed and clamped, and the air exhausted until the gauge registers about 26 inches; that is, the air in the chamber is exhausted until the pressure is the equivalent of about 5 inches of mercury. At this stage the suction is cut off, and the gas is generated in the auxiliary chamber (B) and introduced into the fumigation chamber through the pipe (4). The gas may be generated in one of two ways. The cyanide may be placed in the jar within the generator, the door closed, and the acid and water introduced through the tubulature (5), or the acid may be placed in the jar within the generator and the cyanide in solution introduced through the tubulature (5). The latter method is preferable, especially where a glass tubulature is employed, as it eliminates all possibility of breakage of glass by the heat generated from the combination acid and water. In fact, to prevent breakage, it has been found advisable to cool the acid and water, which reduces the yield of gas. Where the cyanide in solution is introduced through the tubulature, no heat is generated until the solution comes in contact with the acid in the generator. This method has an additional advantage in that the yield of gas is increased."

The material to be disinfected may be fumigated in either of two ways, namely, by generating the gas in the presence of a partial vacuum and holding the vacuum for a definite period, or by generating the gas in the presence of a partial vacuum and returning to normal atmospheric pressure upon the completion of the generation.