APPENDICES. 151 



In charging the generator for the dry gas process, the proper quantity 

 of the potassium-cyanide solution is poured into the lower vessel through 

 the opening closed by the screw-cap, this cap having first been removed, 

 to be again replaced after the solution has been poured in. The stop- 

 cock connecting the two vessels of the generator is next closed by 

 turning the handle attached to the valve, after which the proper 

 quantity of sulphuric acid is poured into the upper vessel. The tin pipe 

 attached to the upper end of the leaden acid-vessel is then removed, 

 and a slightly larger quantity of sulphuric acid is poured into this vessel 

 than was poured into the upper vessel of the generator ; there should 

 be a sufficient quantity of the acid in this leaden vessel to slightly more 

 than cover the end of the leaden pipe leading from the generator. The 

 tin pipe is next attached to the upper end of the acid- vessel, as shown 

 in Fig. 17, while the other end of this pipe passes into the tent 

 previously placed over a tree and made ready for the reception of the gas. 



When everything is ready the handle of the stop-cock of the generator 

 is turned until the acid in the upper vessel commences to flow into the 

 lower one, where it comes in contact with the cyanide solution, and the 

 production of the gas begins. The acid should be allowed to flow very 

 slowly upon the cyanide solution ; if the gas is produced too rapidly the 

 acid will be thrown out of the acid-vessel ; the latter should be taller 

 than indicated in Fig. 17, and it would doubtless be an advantage 

 to have it wider at the top than at the bottom. 



After all of the gas has passed into the tent, the acid in the acid-vessel 

 should be emptied into a glass or leaden vessel to be used the next time 

 for generating the gas ; for this purpose it would be well to insert a 

 brass stop-cock in the lower part of the acid-vessel. There should also 

 be quite a large stop -cock in the lower part of the lower vessel of the 

 generator, for drawing off the residue before again charging the generator 

 with fresh materials. When not in use the two vessels of the generator, 

 and also the acid-vessel, should contain a small quantity of water, which 

 will prevent the valves of the stop-cocks from becoming so corroded 

 that they can not be operated without first being taken apart and cleaned. 



Agitating the Air in the Tent. After the gas has passed into the 

 tent, and also while it is passing in, the air in the tent should be 

 thoroughly agitated. The most effectual method of accomplishing this 

 is by the use of some device whereby the air may be drawn out of the 

 top of the tent and forced in at the bottom. When the McMullen or 

 the Culver tent is used, the pipe taking the air out of the upper part 

 of it can enter the top of the tent, but in the Wolfskill and the Titus 

 tents both pipes must enter the tent at the bottom, the one intended for 

 drawing the air out of the upper part of the tent passing some distance 

 up the trunk of the tree, while the other pipe merely passes a short 

 distance into the tent. 



For circulating the air in the tent various devices have been used, 

 but the one that has given the best satisfaction is known as the 

 Cummin's blower, which was originally intended for forcing air into 

 mines. It consists of an iron fan-wheel, driven with great velocity by 

 means of a series of cog wheels and pinions, the whole encased in an 



