744 REPORT— 1896. 
hot-air current. <A series of four cylinders is required to procure the necessary 
continuity for the process. 
The chlorine gas is washed with a strong solution of chloride of calcium, 
which completely retains all the hydrochloric acid, and is then absorbed in an 
apparatus invented by Dr. Carl Langer, by hydrate of lime, which is made to pass 
by a series of interlocked transporting twin-screws in an opposite direction to the 
current of gas, and produces very good and strong bleaching powder, in spite of 
the varying strength of the chlorine gas. The hydrochloric acid absorbed by the 
solution of calcium chloride can by heating this solution be readily driven out and 
collected. 
This process has now been in operation on a considerable scale at our works at 
Winnington for several years, with constantly improving results, notably with 
regard to the loss of ammonia, which has gradually been reduced to a small 
amount. The process has fully attained my object, viz., to enable the ammonia 
soda process to compete, not only in the production of carbonate of soda, but also 
in the production of bleaching powder, with the Le Blanc process. 
Nevertheless, I have hesitated to extend this process as rapidly as I should 
otherwise have done, because very shortly after I had overcome all its difficulties, 
entirely different methods from those hitherto employed for the manufacture of 
chlorine were actively pushed forward in different parts of the globe, for which 
great advantages were claimed, but the real importance and capabilities of which 
were and are up to this date very difficult to judge. I refer to the processes for 
producing chlorine by electrolysis. 
During the first decade of this century, Humphry Davy had by innumerable 
experiments established all the leading facts concerning the decomposing action of 
an electric current upon chemical compounds. Amongst these he was the first to 
discover that solutions of alkaline chlorides, when submitted to the action of a 
current, yield chlorine. His successor at the Royal Institution, Michael Faraday, 
worked out and proved the fundamental law of electrolysis, known to everybody 
as ‘Faraday’s Law,’ which has enabled us to calculate exactly the amount of 
current required to produce by electrolysis any detinite quantity of chlorine. 
Naturally, since these two eminent men had so clearly shown the way, numerous 
inventors have endeavoured to work out processes based on these principles for the 
production of chlorine on a manufacturing scale, but only during the last few years 
have these met with any measure of success. 
It has taken all this time for the classical work of Faraday on electro-mag- 
netism to develop into the modern magneto-electric machine, capable of producing 
electricity in sufficient quantity to make it available for chemical operations on a 
large scale; for you must keep in mind that an electric installation sufficient to 
light a large town will only produce a very moderate quantity of chemicals, 
In applying electricity to the production of chlorine various ways have been 
followed, both as to the raw materials and as to the apparatusemployed. While 
most inventors have proposed to electrolyse a solution of chloride of sodium, and 
to produce thereby chlorine and caustic soda, I am not aware that up to this day 
any quantity of caustic soda made by electrolysis has been put on to the market. 
Only two electrolytic works producing chlorine on a really large scale are in 
operation to-day. Both electrolyse chloride of potassium, producing as a by- 
product caustic potash, which is of very much higher value than caustic soda, and 
of which a larger quantity is obtained for the same amount of current expended. 
These works are situated in the neighbourhood of Stassfurt, the important centre 
of the chloride of potassium manufacture. The details of the plant they employ 
are kept secret, but it is known that they use cells with porous diaphragms of 
special construction, for which great durability is claimed. There are at this 
moment a considerable number of smaller works in existence, or in course of 
erection in various countries, intended to carry into practice the production of 
chlorine by electrolysis by numerous methods, differing mainly in the details of 
the cells to be used ; but some of them also involying what may be called new prin- 
ciples. The most interesting of these are the processes in which mercury is used 
alternately as cathode and anode, and salt as electrolyte. They aim at obtaining 
