742 REPORT—1896. 
part, also followed up the subject with that tenacity and sincerity of purpose 
which distinguish him, his endeavours being mainly directed to producing 
chlorine direct from the chloride of calcium running away from his works by mix- 
ing it with clay and passing air through the mixture at very high temperatures, 
thus producing chlorine and a silicate of calcium, which could be utilised in cement- 
making. The very high temperatures required prevented, however, this process 
from becoming a practical success. 
I have already told you what a complicated series of operations Dr. Pick has 
lately resorted to in order to obtain the chlorine from this chloride of calcium. 
Yet the problem of obtaining chlorine as a by-product of the ammonia soda process 
presents itself as a very simple one. 
This process produces a precipitate of bicarbonate of soda and a solution of 
chloride of ammonium by treating natural brine or an artificially made solution of 
salt, in which a certain amount of ammonia has been dissolved, with carbonic acid. 
In their original patent of 1838 Messrs. Dyar and Hemming proposed to evaporate 
this solution of ammonium chloride and to distil the resulting dry product with 
lime to recover the ammonia. Now all that seemed to be necessary to obtain the 
chlorine from this ammonium chloride was to substitute another oxide for lime in 
the distillation process, which would liberate the ammonia and form a chloride 
which on treatment with atmospheric air would give off its chlorine and reproduce 
the original oxide. The whole of the reactions for producing carbonate of soda 
and bleaching powder from salt would thus be reduced to their simplest possible 
form; the solution of salt, as we obtain it in the form of brine direct from the soil, 
would be treated with ammonia and carbonic acid to produce bicarbonate and 
subsequently monocarbonate of soda ; the limestone used for producing the carbonic 
acid would yield the lime required for absorbing the chlorine, and produce bleaching 
powder instead of being run into the rivers in combination with chlorine in the 
useless form of chloride of calcium ; and both the ammonia used as an intermediary 
in the production of soda and the metallic oxide used as an intermediary in the 
production of chlorine would be continuously recovered. 
The realisation of this fascinating problem has occupied me for a great many 
years. In the laboratory I obtained soon almost theoretical results. A very large 
number of oxides and even of salts of weak acids were found to decompose 
ammonium chloride in the desired way ; but the best results (as was to be clearly 
anticipated from thermo-chemical data) were given by oxide of nickel. 
When, however, I came to carry this process out on a large scale, I met with 
the most formidable difficulties, which it took many years to overcome successfully. 
The very fact that ammonium chloride vapour forms so readily metallic chlo- 
rides when brought in contact at an elevated temperature with metals or oxides, 
or even silicates, led to the greatest difficulty, viz., that of constructing apparatus 
which would not be readily destroyed by it. 
Amongst the metals we found that platinum and gold were the only ones not 
attacked at all. Antimony was but little attacked, and nickel resisted very well if 
not exposed to too high a temperature, so that it could be, and is being, used for 
such parts of the plant as are not directly exposed to heat. The other parts of the 
apparatus coming in contact with the ammonium chloride vapour I ultimately 
succeeded in constructing of cast and wrought iron, lined with fire-bricks or 
Doulton tiles, the joints between these being made by means of a cement consisting 
of sulphate of baryta and waterglass. 
After means had been devised for preventing the breaking of the joints 
through the unequal expansion of the iron and the earthenware, the plant so 
constructed has lasted very well. 
Oxide of nickel, which had proved the most suitable material for the process. in 
the laboratory, gave equally good chemical results on the large scale, but occasion- 
ally a small quantity of nickel chloride was volatilised through local over-heating, 
which, however, was sufficient to gradually make up the chlorine conduits. We 
therefore looked out for an active material free from this objection. Theoretical 
considerations indicated magnesia as the next best substance, but it was found that 
the magnesium chloride formed was not anhydrous, but retained a certain amount 
