June, I93s.l CURRENT TOPICS. 779

direction. The gases enter through an opening in the drum arranged tangentially and extending from the bottom to a point about a quarter of the depth from the top; they escape through a central pipe. The effect of the double eddy has been shown to be sufficiently marked to neutralize completely and even overcome the centrifugal action due to the swirl of the gases in the horizontal plane in the positions in which it is directly opposed to this action. The result is that the dust accumulates at the top until its mass is sufficient to overcome the pressure of the upward current. When this occurs the dust slides down into the hopper where the bottom current assists its descent. The dust may be removed from the top of the drum by means of the external by-pass. The second feature of this separator is an opening with deflecting vanes in the prolonged outlet pipe or chimney at a point where centrifugal action and eddy currents are carrying the dust away from it, so that any gas passing through it will come from the area which is most free from dust. A third feature is that in the normal arrangement there are two drums, viz., a primary drum and a secondary drum, the latter being integral with the dust collecting hopper. The overall efficiency of the plant was shown by tests to be 96. I per cent. For dust of 60 microns diameter and over the efficiency was 99.5 per cent., and for dust of 40 microns and over it was 99.1 per cent.

R. H. 0.

Rayon from Sugar Cane.-Working in the laboratories of the Bureau of Chemistry and Soils, D. F. J. LYNCH has perfected a process for the manufacture of alpha cellulose from sugarcane bagasse. Bagasse-the refuse from sugarcane mills-offers interest- ing possibilities since there is no problem of collecting this raw material at the factory as there would be in the case of corn stalks. It has already been accumulated in great quantities at the sugar mills and in the past has been useful mainly as fuel. In recent years wall boards have been made from bagasse, but this outlet is limited.

The process uses dilute nitric acid as the pulping agent. This acid is now relatively cheap because of the availability of large quantities of liquid ammonia. The nitric acid process as developed gives higher yields and purer cellulose from bagasse than those obtained from any of the standard commercial pulping methods.

This summer, the nitric acid process is to be tried out in Hawaii on a semi-commercial scale. There is every promise that a high grade cellulose approaching that made from cotton linters will be the result. Should the tests prove satisfactory, additional plants undoubtedly will be built in Louisiana and Puerto Rico.

C.