66 PROCEEDINGS OF SECTION B. 



ammonia comes first and carbonic acid last. Carbonic acid 

 machines, however, have the advantage of being much more com- 

 pact, since they work at higher pressures, and carbonic acid has 

 the further advantage over ammonia and sulphuric dioxide that it 

 has no offensive odour and is not corrosive ; consequently, for 

 refrigerating on ships carbonic acid machines are now displacing 

 the more efficient ones using ammonia. 



Refrigerating machines are now being employed for a variety 

 of purposes, amongst which may be mentioned the cooling of wort 

 in breweries, the preservation of food on land and sea, ice-making, 

 butter-making, and the manufacture of explosives and chemicals. 

 The Americans have gone further, and in some towns, notably at 

 Louisville, cold is supplied from a central station to the houses and 

 shops of consumers. Liquid ammonia is sent out under pressure in 

 mains buried in the streets, and is admitted as wanted to refrigerating 

 coils on the premises of each consumer. The latter can obtain any 

 amount of refrigeration he pleases by regulating the amount of 

 ammonia admitted to his evaporating coils. The gaseous ammonia 

 returns to the generating station through a second main. 



Another important use for gases is in connection with processes 

 of disinfection. 



For houses, ships and other enclosed spaces, sulphur dioxide 

 and formahn vapour are most commonly employed, and enormous 

 quantities of formalin are now being used for disinfection purposes. 

 For ship use, the method I have brought forward of carrying 

 formalin vapour in a current of cooled and cleaned flue gas to the 

 various parts of the ship will, I hope, be of some service. In 

 orchards extensive use is made of prussic acid generated from 

 cyanide and sulphuric acid, and this gas is now largely used for 

 destroying vermin in houses, and moths and other insects in flour 

 mills, etc. 



While on the subject of disinfection the employment of gases 

 for fire extinction can be touched upon. 



Liquid carbonic acid is now being largely used by the fire 

 brigades all over the world. The pressure of the gas in the cylinders 

 forces the water to the seat of the fire and at the same time charges 

 it with gas which materially assists in keeping away the air from 

 the burning material. 



Carbonic acid gas is also used for ship fires ; but for this purpose 

 the gas itself is projected into the burning hold. Owing to the large 

 quantity of gas required to effectively deal with a fire in the hold of 

 a ship the apphcation of carbonic acid has very distinct limitations, 

 and I venture to believe that the method I have introduced — which 

 consists of displacing the air in the hold by means of cleaned and 

 cooled flue gas, taken from the fimnel of the ship itself, will prove 

 of real service. 



