Vor.. 2, No. 9
STUDY OF PUPILSERRORS I N CHEMISTRY
769
VIII, we find the tartrate radical presents the greatest difficulty, followed by the acetate radical and by the element aluminum. The valence of oxygen is the easiest to remember, among those included in the 45 formulae considered. Lastly, in Table X I , we are comparing items in the Powers study which are included also in this study. While the absolute percentages are not comparable, as the testing conditions were not the same in the two studies, still there are some interesting comparable points as to relative difficulty of certain tasks. Of formulae common to both investigations, the tartrates are the most difficultto write, while ferrous sulfate is an easy one. In the list of equations common to both studies, the equation for the action between copper and nitric acid is unmistakably the-most difficult: that for the action of sodium on water, also, is difficult: while the equation for the union of oxygen and hydrogen is easy. In gas-volume problems, the pressure problems seem slightly more difficult than the temperature problems. But none of the problems common to the two studies are on the whole as difficult as problems based on the law of multiple proportion.
REVOLUTIONIN MAKING GAS FUEL INDICATED BY WYOMING EXPERIMENT
Gas engineers and gas men generally are watching with considerable interest the experiment of a small gas company in Sheridan, Wyorging, which is using the local lignite deposits, which are mined adjacent t o the city, for the manufacture of coal gas supplied to the residents and industries of Sheridan for heating and cooking purposes. This is believed t o be the first time that lignite has ever heen used successfully in coal gas manufacture to the entire exclusion of other materials, and, if applicable to other gas companies, may result in untold economies by eliminating high freight rates and the necessity of using.high -~ priced gas or coking coal. The use of lignite coal has already made a material difference in coal cost in Sheridan, and the city is benefited by the $2100 per month now being spent there, in addition to the reduced rate in gas which this has helped to bring about, not only owing to the lower price and greater efficiencyaf the coal, but the great saving on freight. Southern Colorado coal used to cast the company $378 per carload for shipment in comparison to the $15 to $18 which it now pays. Writing in the American Gas Association Monthly, H.J. Forward, manager of the Sheridan Gas and Fuel Company, says: "After conducting experiments with lignite coal for three years, I am thoroughly convinced that in the future large quantities of this so-called low grade fuel will be used for gas-making purposes. I believe that gas plant operators, particularly those within a reasonable distance from lignite coal fields, will find it well worth their while t o investigate its possibilities." Mr. Fonvard says that gas supplied to the city of Sheridan from lignite coal will average 535 B. t . u. per cubic foot, which is well within thelegal limits set by most state commissions.
