456 Sir Henry Boscoe [^lay 3, 



gasometers are filled in turn from the stills, the chlorine consumed 

 being taken direct from a gasometer under a regular pressure until 

 it is exhausted ; the valves being changed, the supply is taken from 

 another holder, the emptied one being refilled from the still. 



Manufacture of the Double Chloride. 



Twelve large regenerative gas furnaces are used for heating, and 

 in each of these are fixed five horizontal fire-clay retorts about 10 ft. 

 in length, into which the mixture for making the double chloride is 

 placed. These furnaces have been built in two rows, six on a side, 

 the clear passage-way down the centre of the building, which is about 

 250 ft. long, being 50 ft. in width. Above this central passage is the 

 staging carrying the large lead-mains for the supply of the chlorine 

 coming from the gasometers. Opposite each retort, and attached to 

 the main, are situated the regulating valves, connected w^ith lead and 

 earthenware pipes, for the regulation and passage of the chlorine to 

 each retort. The valves are of peculiar design, and have been so 

 constructed that the chlorine is made to pass through a certain deptli 

 of liquid, which not only by opposing a certain pressure allows a 

 known quantity of gas to pass in a given time, but also prevents any 

 return from the retort into the main, should an increase of pressure 

 be suddenly developed in the retorts. 



The mixture with which the retorts are charged is made by 

 grinding together hydrate of alumina, salt, and charcoal. This 

 mixture is then moistened with water, which partially dissolves the 

 salt, and thrown into a pug mill of the usual type for making 

 drain pipes, excepting that the mass is forced out into solid cylin- 

 drical lengths upon a platform alongside of which a workman is 

 stationed with a large knife, by means of which the material is cut 

 into lengths of about 3 inches each. These are then piled on top of the 

 large furnaces to dry. In a few hours they have sufficiently hardened 

 to allow of their being handled. They are then transferred to large 

 wagons, and are ready to be used in charging the retorts. 



The success of this process is in a great measure dependent — 

 1st, on the proportionate mixture of materials ; 2nd, on the tem- 

 perature of the furnace ; 3rd, on the quantity of chlorine introduced 

 in a given time ; and 4th, on the actual construction of the retorts, 

 I am, however, not at liberty to discuss the details of this part of the 

 process, which have only a commercial interest. In carrying on the 

 operation, the furnaces or retorts, when at the proper temperature, 

 are charged by throwing in the balls until they are quite full, the 

 fronts are then sealed up, and the charge allowed to remain undis- 

 turbed for about four hours, during which time the water of the 

 alumina hydrate is completely expelled. At the end of this time 

 the valves on the chlorine main are opened, and the gas is allowed 

 to pass into the charged retorts. In the rear of each retort, and con- 

 nected therewith by means of an earthenware pipe, are the condenser 



