Charge the generator with the required proportions of carbonate and water. The usual proportions are for -

Marble Dust

1 gall, sulphuric acid = 2 galls, marble dust=4 galls. of water; or 2 galls, sulph. acid=5 galls, of marble dust=7 1/2 to 10 galls, of water. If the materials are of inferior quality, it is necessary to vary these proportions, and many manufacturers prefer to use the marble dust rather in excess, since it is cheaper than the acid, than to have the latter in excess. When marble dust is used, the agitator should be turned every few minutes after the dust is put into the alkali-chamber, to prevent the mass from setting and causing the agitator to stick; the marble dust is poured into the water in generator, which was previously introduced.

Whiting

To expel all the gas from whiting it takes in practice about equal weights of acid and whiting. The exact proportion is: 98 lbs. of sulphuric acid and 100 lbs. of whiting. The whiting should be mixed with water to a consistency somewhat thicker than thick whitewash before being put into the generator, if it is in a lumpy condition. When the whiting is in a powdered state, its mixing with water before going into the generator is quite unnecessary and is a disadvantage, it taking extra time and soils the factory. The whiting should be put into the generator dry, and when water is let on to it it is easily mixed to the consistency of batter by means of the agitator, or the whiting may be poured into the water previously introduced.

Marble Dust And Bi-Carbonate Of Soda

Some manufacturers use about one pound of bi-carbonate of soda to every gallon of marble dust. It facilitates the cleansing of the generator after the charge is exhausted to some extent, but is in general of no practical utility, except that the quality and quantity of the gas will be somewhat improved. When added in larger proportions, the gas, of course, will be generated more freely and agitation rendered easier, but it would be too expensive for everyday use.