Oct.. 1935.1 CURRENT TOPICS. 533

usually are more or less heterogeneous and variable in composition and contain . . . considerable quantities of inert or even objec- tionable impurities.” The remarkable influence of an efficient inhibitor is better appreciated when it is realized that one-hundredth of a mol of phenylacridine exerts 92 per cent. inhibiting power and a like proportion of 3,6 dimethyl 1-2-7 diethyl aminoacridine hydro- chloride is 99.8 per cent. effective.

Naturally, the most extensive use of inhibitors will be found in pickling operations where the acid is used to dissolve away scale and oxides and minimum attack on the metal is desired. The same principle is applied in dairies where it is sometimes necessary to dis- solve from equipment a dense lime scale using acid with an inhibitor to protect the metal parts. A more recent application comprises a process for the reactivation of dormant or exhausted oil wells. This involves the pumping of hydrochloric acid down the pipes where it attacks the calcareous formations. An inhibitor prevents the acid from dissolving away the steel casings and iron pumps but does not interfere with destruction of the calcite.

C.

Making Bread from Hydrogen Peroxide instead of Yeast. (Chemical Industries, August, 1935.) At a recent meeting of the American Association of Cereal Chemists L. H. BAILEY and J. A. LECLERC described the use of hydrogen peroxide to replace yeast in breadmaking. It was found that the hydrogen peroxide bread had slightly more crust than the yeast bread, and its moisture content was a little lower. The peroxide bread contained approximately three times as much sugar and soluble nitrogen as the material made from yeast. It likewise contained twice as much water- soluble solids and slightly less soluble starch. The percentages of fat, ash, and total nitrogen in both breads were the same. The peroxide bread possessed as good a grain and better texture than the corresponding yeast bread. The loaf of the former was fully as large as the latter but, and here’s the catch, the flavor of the peroxide bread was poor, as the flavor of ordinary bread is largely due to yeast activity.

L.

Cathode-Ray Oscillograph Engine Indicator.-_( Engineering, Vol. CXL, No. 3632.) The cathode-ray oscillograph has the unique freedom from inertia required for the measurement of pressure changes of high frequency, and the application of the instrument to indicate the process of combustion in an engine cylinder has engaged the attention of the research staff of the Anglo-American

536 CURRENT TOPICS. [J. 1;. 1.

Oil Co. for the past five years. The development work has now reached the stage that diagrams can be taken free from spurious vibration and mechanical or electrical lag at any engine speed, and even when detonation is in progress. It has been used satisfac- torily in the laboratories to determine the combustion character- istics of various fuels in spark ignition engines, and for the deter- mination of ignition characteristics in Diesel engines.

A particular advantage of the instrument lies in the fact that any desired portion of the engine cycle can be selected and magnified on the time base, thus enabling a very close study to be made of such phenomena as ignition lag in Diesel engines and detonation in petrol engines, both of which occur during such a small crank- angle that analysis is practically impossible on the conventional pressure-time diagram. The instrument may also be adjusted to obtain diagrams on a stroke base.

Visual observation of diagrams can be made conveniently, or can be recorded photographically. Such an instrument will doubt- less become a factor in the further development of the internal combustion engine.

R. H. 0.

The Bus of 1940.-A very interesting forecast of the type of bus the public will be riding in in 1940 is given in a paper by R. A. HAUER before the recent meeting of the Midwest Transit Associa- tion in Denver, an abstract of which appears in the Transit Journal for August, 1935. Many important changes will be evident. Fuel costs per ton mile will be less. Engines will have higher thermal efficiency, and improved transmissions will permit the engine to operate at more nearly their economy peak than at present. It is possible that other and more economical fuels may be available. The diesel is showing more promise daily and the development of butane-propane fuel may possibly provide an answer. Either force may parallel developments on gasoline engines. In 1940 pIT3CtiCally

all new buses will have rear-mounted engines and there will doubt- less have been developments along somewhat unconventional lines as to cylinder arrangement, such as division at the middle, with the clutch drive take-off from the center of the crankshaft; a swashplate engine; or a tight V arrangement. The bus of 1940 will be defi- nitely lighter for the same capacity and performance. It will have a low floor, no ramps or steps inside. Long distance buses will be as thoroughly air conditioned as trains, but it is doubtful if air con- ditioning will be attempted in city type buses. Heaters may be located above the windshield with fresh air blown in over them, foul air outlets being located at the rear and near the floor, and of