L, NORMAN SELFE. 
in another condenser, after which the ammonia from the refriger- 
ator and the mother liquors are allowed to re-unite in 4 vessel 
termed the absorber, from which the system takes its name; after 
this it can be returned to the boiler to go through the same cycle 
of operations over and over again. It will thus be seen that this 
is a very simple process, for, besides the several vessels, coils and 
valves, there is no machinery proper required beyond the pump to 
return the liquor from the absorber to the boiler, and even that 
can be dispensed with by ingenious arrangements like the “ Monte- 
jus” whereby the strong liquor is lifted by pressure to a receiver 
and descends to the still by gravity. This class of machinery 
being cheap and the process simple, absorption machines are still 
made and used under certain conditions, and many elaborations 
have been made to secure fractional distillation and dessication 
of the gas, and also by means of exchangers to utilise some of the 
waste heat, but it is perhaps more on account of the greater 
amount of condensing water required, than the greater power 
wasted in the absorption machine, that the compression system 
has replaced it. 
Water, at atmospheric pressure and 60° Fahr., will absorb about 
‘seven hundred times its volume of ammonical gas, and therefore 
the watery vapour that distills over with the gas largely discounts 
the efficiency of the machine, because it not only requires fuel to 
raise it, but a supply of cold water to condense it, and although 
increasing the amount of fuel required for a compression plant 
might not alone condemn the use of the absorption system where 
fuel is cheap, yet in most parts of Australia the requirement of 
‘double the quantity of condensing water would be a serious draw- 
back, and has led to great numbers of them being replaced by 
‘compression machines. 
MECHANICAL COMPRESSORS FOR AMMONIA. 
As soon as the defects inseparable from the absorption syste™ 
were understood, inventors reverted to the work of Jacob Perkins, 
Harrison and Twining, but it was a very different matter 
“compressing a subtle gas like ammonia up to twelve or more 
