566 U. S. BUREAU OF CHEMISTRY NOTES. [J. I;. I.

recognize the direction in the crystal in which addition of the CH, group, the H,O of crystallization, and the acetyl groups takes place. The substances are too soluble in the liquids ordi- narily used for the study of optical properties by the immersion method to permit accurate determinations of their refractive indices to be made.

Producer Gas for Internal Combustion Engines.-The short- age of gasoline in Great Britain during the war led to extensive investigations for substitutes, among which were ordinary illu- minating gas and producer gas. A report has just been published by the committee appointed to investigate the subject, an .ab- stract of which is given in the English Mechanic (vol. cx, p. 31, 1919). The committee considers that gas traction is as safe as the ordinary form even when unprotected and exposed flexible containers are used. In its newer forms it is well worth consid- eration as an alternative of electric, gasoline or steam traction. Common city gas is estimated to be equivalent to gasoline in the proportion of 250 cubic feet of the former to I gallon of the latter. Presumably, these being English data, the city gas is more largely hydrocarbons than much of the gas supplied to American cities, and the gallon may be the itnperial gallon of ten avoirdupois pounds. It is recommended, however, that gas-bags should be replaced by rigid or semi-rigid containers, whenever a compres- sion plant can be installed, but it is not considered advisable that any existing plant for gas-traction should be abandoned at this time. Figures on cost of compressing, etc., are given, but they are obviously of no value in this country.

In a supplementary article (E. M., same volume, page 45) Mr. David J. Smith, who made many of the experiments in the matter, states that it is possible to run satisfactorily in competi- tion with gasoline tnotor vehicles by producing gas made on the vehicle, using anthracite, coke or charcoal. He states that the cost of running a truck with anthracite at 50 shillings ($11) per ton was equivalent t’o gasoline at 5.4 pence (I I cents) per gallon, th,e commercial rate of the gutiline ‘being taken at zs.6d. (about 60 cents) per galllon. He claims that a producer can be made accord- ing to his designs that will occupy no loading room on the truck, and free access to the equipment is secured. In case of trucks the weight of the equipment for producing the gas does not exceed z per cent. of the weight of the loaded vehicle. The method is applicable to boats and tractors, the small size of the plant rendering it suitable for applications to which formerly producer gas apparatus could not be applied.

H. L.