1873.] 



On the direct Synthesis of Ammonia. 



281 



uniformly as the pressure of air increases from two to ten per cent, that 

 of the steam, and then less and less rapidly until thirty per cent, is 

 reached, after which the rate of condensation remains nearly constant. 



3. That in consequence of this effect of air the necessary size of a surface- 

 condenser for a steam-engine increases very rapidly with the quantity of 

 air allowed to be present within it. 



4. That by mixing air with the steam before it is used, the condensa- 

 tion at the surface of a cylinder may be greatly diminished, and conse- 

 quently the efficiency of the engine increased. 



5. That the maximum effect, or nearly so, will be obtained when the 

 pressure of the air is one tenth that of the steam, or when about two 

 cubic feet of air at the pressure of the atmosphere and the temperature 

 60° F. are mixed with each pound of steam. 



15. Remarks. As this investigation was nearly completed my atten- 

 tion was called to a statement by Sir W. Armstrong, to the effect that 

 Mr. Siemens had suggested as an explanation of the otherwise anomalous 

 advantage of forcing air into the boiler of a steam-engine, that the air 

 may prevent, in a great measure, the condensation at the surface of the 

 cylinder. It would thus seem that Mr. Siemens has already suggested 

 the probability of the fact which is proved in this investigation. I am 

 not aware, however, that any previous experiments have been made on 

 the subject, and therefore I offer these results as independent testimony 

 of the correctness of Mr. Siemens's views as well as of my own. 



II. " On the direct Synthesis of Ammonia." By W. F. Donkin. 

 Communicated by Sir B. C. Brodie, Bart., F.B.S. Received 

 May 1, 1873. 



The action of induced electricity on mixtures of certain gases has been 

 lately shown by Sir Benjamin Brodie (Proc. Roy. Soc. April 3, 1873) to 

 yield very interesting results. 



An obvious application of his method was to treat a mixture of dry 

 hydrogen and nitrogen in a similar manner as those referred to above, 

 with the view of effecting the synthesis of ammonia ; and Sir B. Brodie 

 kindly allowed me the use of his apparatus for the purpose of the 

 experiment, which was conducted as follows : — 



A mixture of about three volumes of hydrogen with one of nitrogen in 

 a bell-jar over water, was passed through two tubes containing pumice 

 moistened with alkaline pyrogallate and sulphuric acid respectively, then 

 through a Siemens induction-tube, and into a bulb containing dilute 

 hydrochloric acid, The whole apparatus being first filled with pure 

 hydrogen, about half a litre of the mixed gases was sent through the 

 apparatus, the induction-coil not being in action ; the bulb containing 

 the acid was then removed and another substituted, containing an equal 

 volume of the same acid. 



