lOG REPORTS ON THE STATE OP SCIENCE. — 1919. 



the heat units actually received by each individual gas consumer 

 tlu'oughout the Kingdom, and {h) that certain other conditions (herein- 

 after set forth) were assured, it would be more equitable to charge the 

 consumer on a basis of ' heat units ' than on one of ' cubic feet ' 

 supplied. 



(3) The Committee also agrees generally with the Fuel Eesearch 

 Board's recommendations as to (a) the maximum limit of 12 per cent, 

 of inert constituents, and (5) the minimum pressure of two inches of 

 water in the gas at the exit of the consumer's meter. 



(4) The Committee considers that it should be the aim of any national 

 policy in regard to gas standards to ensure (a) to the consumer, and 

 especially to the domestic consumer, a supply of gas suitable to his 

 requn^ements at the lowest cost consistent v/ith reasonable safety, and 

 [b) to the community at large, as great a recovery of valuable by-products 

 in the carbonising process as is consistent with the production of a 

 reasonably safe and usable gas. It certainly ought not to exclude the 

 possibility of (a) distributing through the public mains surplus coke- 

 oven gas or [b) securing, to a safe and reasonable degree, the advantages 

 in regard to reduced costs of production accruing from the modern 

 practice of steaming the incandescent coke produced by carbonising 

 coal in vertical retorts on the continuous system. It by no means 

 necessarily follows, however, that a gas undertaking ought tO' convert 

 all its coke into water gas, as some of them apparently would like to do. 

 It might conceivably be better policy to require gas undertakings, or 

 at least some of them, to produce and supply the community with (a) a 

 straight coal gas obtained simply by carbonising the coal, and (6) a 

 free-burning coke, or semi-coke, fit for consumption in domestic grates. 



(5) From information supplied to the Committee it would appear 

 that, with regard to the quality of the gas generally supplied to con- 

 sumers in days immediately preceding the war, the following figures 

 may be quoted for the average gross calorific values, per cubic foot 

 at 60° Fahr. and 30 in. barometer, of the gas supplied during the year 

 1913 in six of the largest cities of Great Britain : — 



'&"- 



620, 596, 593, 582, 580, and 540 B.Th.Us. 



Whilst it may be freely admitted that calorific value, although always 

 an important one, is by no means the only factor to be considered in 

 selecting a gaseous fuel for any particular purpose, the Committee is 

 of the opinion that the proposal of the Fuel Research Board that in 

 future gas undertakings may be allowed to supply, at their sole dis- 

 cretion, gas of any calorific value between 400 and 500 B.Th.Us., ought 

 to be very carefully scrutinised in all its bearings, especially as it involves 

 a considerable dilution of the old ' coal gas ' by ' water gas,' with conse- 

 quent much higher carbonic oxide and lower methane contents. Indeed 

 the Fuel Research Boaixl holds that * the natural diluent for coal gas 

 is water gas, made either from coke in a separate producer, or in retorts 

 by steaming the hot coke. ' 



(6) The composition of the gas obtainable by carbonising British gas 

 coals at high temperatures either in modern vertical retorts or coke 



