3io CURRENT TOPICS. [J. F. I.

anode was made by packing into a quartz tube powdered graphite and a halogen salt of the metal to be examined. When the discharge passes, there is a glow on the surface of the anode and a beam comes out from the surface. A fine pencil of this beam of anode rays is separated by letting the whole fall on a tube having in it a hole only .2 ram. in diameter. The small pencil that gets through is then subjected to the simultaneous influence of magnetic and electro-static fields whereby the rectilinear ray is bent into a parabolic form from whose dimensions it is possible to calculate the atomic weight of the atoms in the ray. The form of the parabola is recorded on a pho~ographic plate.

Lithium is found by Mr. Thomson to consist of isotopes having atomic weights of 6 and 7. The line due to the 6 constituent was " sometimes considerably stronger than would be expected from the atomic weight, 6.94." Beryllium gave no sign of having atoms of atomic weight different from 9- Calcium and strontium lay with- out the limit of the resolving power of the apparatus used. " It is, however, certain that one or more of the atomic weights (39, 4o and 4I) ' were present (i.e., when calcium was tried) ; and as all these are already known to exist as isotopes of other elements (39 and 4o potassium, and 4o argon), it is clear that calcium is an instance of a so-called isobar. No previous instance had been known except among the radio-active elements."

It is to be hoped that the word " i sobar" in this sense will be replaced by some other term, since isobar already has quite a different meaning in meteorology.

G. F. S.

Selenium and Tellurium Campounds as Intensifiers of Gasolin. (Am. Chem. Soc. News Serv.)--Authoritative reports from the laboratories of the General Motors Company give infor- mation that by the employment of selenium oxychloride or diethyl telluride the efficiency of a given amount of gasolin can be doubled. The data have been obtained by Midgley and Boyd. The tellurium compound was the most efficient, and is especially advantageous in eliminating the " knock " which is developed when a motor is laboring on a grade. Victor Lenher states that if only one hundred of one per cent. should be used in gasolin, the amount of tellurium required in the present use of gasolin in the United States will be I5O~ tons. In I92o it was ascertained that without further plant equipment the

c o u n t r y could reduce only a little over sixty short tons. It will be necessary to find new sources of tellurium and also of selenium if these materials are to be extensively employed. A very important point will be the sanitary problems, which apparently have not yet been considered. Selenium and tellurium compounds are mostly quite poisonous.

H . L .