In such an arrangement, it is desirable, in order to obtain good efficiency in the high-pressure range, to adopt a separate fast running high-pressure turbine. The three-turbine arrangement, consisting of high-pressure, intermediate-and lowpressure turbines geared to the propeller shaft, is specially applicable under such conditions. Assuming such a design to be adopted for an installation of about 5ooo S.H.P. with boiler pressure 5oo pounds, superheat temperature 7oo ยฐ F., feed heating to 35 oยฐ F., and effective air preheating to give a boiler efficiently when fired by fuel oil of about 84 per cent., a careful estimate based on known performance shows that owing to the increased available energy of the steam, a fuel consumption of about .57 pound per S.H.P. would be obtained for turbines only, and .69 pound per S.H.P. including auxiliary machinery.
When the difference in price between fuel oil and Diesel oil is taken into consideration, these being in about the ratio of 3 to 4, and also allowance made for the cost of lubricating oil for the Diesel engine in excess of that for the turbine, it will be seen that these figures are equivalent to about .38 pound of Diesel oil per S.H.P. for turbines only, and .475 pound Diesel oil per S.H.P. for all purposes, including auxiliary machinery, and therefore promise an economy in cost of fuel superior to that obtained with Diesel engines; whilst the first cost of such an installation will be little, if any, greater than that of a geared turbine installation of the usual design with low pressures and moderate superheat, and considerably less than the cost of an oil engine.
To sum up : By practical application of the principles discussed above to the expansion of steam in a turbine, overall thermal efficiencies can be realized which are not inferior to those of internal :ombustion engines.
It will also be seen that by raising the boiler pressure to 2ooo pounds per square inch, the Carnot cycle is closely approached and the maximum possible efficiency obtained consistent with the limits of temperature assigned by the endurance of metals at high temperatures.
Atomic Weight of Antimony.--PHILIP F. WEATHERILL, Of the University of Michigan (]our. Am. Chem. Soc., I924, 45, 2437-2445), has determined the atomic weight of antimony by the analysis of antimony trichloride. The value obtained is I21.748 ยฑ o.ooo86.
J. S. H.