NITROGENOUS MANURES. 229 



to redness, which lowers the temperature, owing to the heat ab- 

 sorbed by the decomposition of water. 



2. The combustion is stimulated by a current of air to bring the 

 temperature to its initial point. 



The gas produced in this second phase very much resembles gas 

 from a gas generator, called Siemens' gas. The mixture of air and 

 steam is suitably adjusted. Amongst the gasogene plant constructed 

 on this principle mention may be made of Siemens', Schilling's, 

 Powson's, Wilson's and Mond's. 



1. Mould's Process. — Mond was the first to inaugurate in 

 England this new process of extracting ammonia from the products 

 of combustion of coal itself. Coal is burnt in the gas generator in 

 a mixture of air and steam, in such proportions that there are two 

 tons of steam per ton of coal distilled. The temperature of the 

 combustion is lowered to about 500'^ C. (932' F.). This excess of 

 steam favours the production of ammonia ; the third only of the 

 steam which passes through the gasogene is decomposed. The gas 

 producers are rectangular in form and arranged in series. They are 

 1-82 metres in depth and 3*65 metres long. The ash pits fitted 

 with a hydraulic joint capable of resisting 0"10 metre water pres- 

 sure. The air arrives above the level of the ash pit. The gas 

 escapes from the centre of the top of the gas producer. 



The gas which escapes from the gas producer traverses a w^asher 

 with blades. Standard type, in which the ammoniacal salts are 

 dissolved. Then at a temperature of 100'^ C. it passes into the first 

 scrulDber, drenched with a 38 per cent solution of sulphate of 

 ammonia to which a known amount of sulphuric acid has been added. 



The gas contained at its entrance into the scrubber 0"13 per cent 

 of ammonia by volume, it now only contains 0"013 when it issues 

 at a temperature of 80" C. It then enters the condenser 

 containing wooden battles pierced with holes, where they meet 

 a current of water which is heated to 78" to 80' C. (172-4' to 176' E.) 

 in condensing the steam. The gas, purified and cooled, passes to 

 the burners. The hot water obtained passes to a third scrubber, into 

 w^hich a current of cold air is passed, which it saturates with mois- 

 ture, and which brings the temperature to 76° (168'8° F.). That air 

 is then forced into the gas producer. The yields obtained have 

 been 32 kg. (70*4 lb.) of sulphate of ammonia per ton of coal, which 

 is a beautiful result. 



Attempts have been made to produce ammonium chloride 

 direct by introducing hydrochloric acid gas into the furnace or by 

 mixing the fuel with clay impregnated by calcium chloride. The 

 results were not satisfactory. 



Hennin proposes to operate like Mond, but by using high 

 pressure steam slightly superheated and suitably diffused in the 

 mass of the fuel, in the proportion of 0*75 to 1 per ton of coal. 



