SCIENCE NOTES.

Digger (Invercargill RSA), Issue 42, 7 January 1921, Page 13

SCIENCE NOTES.

DE-TANNING CHROME LEATHER. A British patent has recently been issued covering a process whereby scrap leather may be de-tanned and the resulting material used for the manufacture of glue and gelatine. The chrome leather is first immersed in a solution of an organic acid, such as phthallic, lactic, tartaric, oxalic, or other organic aoids containingtwo or more hydroxyl groups. The chromium may be recovered from the resulting solution and the de-tanned ipaterial treated in the usual manner for making glue or other similar products. TEST EOR CONCRETE MIXTURE. As the strength oi a coricrete mixture is much afiected by the amount of water contained, the novel apparatus of the United States Bureau of Standards is designed to give an accurate test of the fluidity or flow. A circular table-top mounted on a plunger is raisecl and dropped half-an-inch by a cam on the shaft of a hand-crank. A sample of the mixture, moulded into a truncated cone six inches tall "and eight to twelve inches in diameter, is placed in the centre of the table, and the crank is given fifteen revoiutions. The average diameter to which the sample is spread out is divided by the original diameter and multiplied by 100. The result is the flowability numiber — 150 indicating a strong material for bricks, and 225 one suitable for r,einforced concrete. TUNNEL ATMOSPHERE. The Bureau of Standards in the United States has been requested to undertake an investigation of the atmospheric conditions which would be likely to exig^ in such a tunnel as is projeeted to comSfect Manhattan Island with New Jersey. In this study particular account must be taken of the exhaust gases from motor vehides, in which, as is well known, carbon monoxide is to be found. Road tests have been begun with some eighty motor vehicles of different classes, and the results obtained from these tests differ somewhat from tlxe block tests which have heretofore been conducted. In the near future a series of chamber tests on human subjects will be started and these chambers will be designed to represent cross-sections of the tunnel as it is now designed. Inasmuch as there are similar tunnels under consideration for other cities, the work in question assumes increased importance. IMPROVED STEELMAKING. An improvement of the acid Bessemer steel process which aims to reduce the cost of making steel and to decrease the possibility of low quality steel in the process has been recently invented by a member of the department of mining and metallurgy at the University of Wisconsin. The purpose of the invention is to use basic material for the lining .of the Besseiaer converter instead of the acid lining now used in order to prevent corrosion of the interior of the converter and to reduce the amount of air pressure and engine power now required. With the basic lining, composed of lime, magnesite, dolomite, oxid,e of iron, or the like, the inventor believes it will be possible to use lower pressure and cut down the time of blowing about 30 per cent. To prevent corrosion of the converter bottom the inventor proposes a number of different kinds of linings for various acid Bessemer converts and details the particuuar parts of the converter that require such a basic lining, while the remainder of the converter has an acid lining to resist corrosion by the acid slag. INDUSTRIAL USE OF GAS MASKS. Gas masks of a nose-breathing type with canisters containing special chemicals are used in the digester house of the Forest Products Laboratory, Americ'a, to give protection against sulphur dioxide. These masks enable the operator to make. repairs under conditions otherwise uubearable and soon pay for themselves in time saved. Masks of this type are rep.orted by the Bureau of Mines to hold up against a 5 per cent. concentra-tion of sulphur dioxide for about 15 minutes. When it is realised that five parts of the sulphur dioxide to one million parts of air can readily be detected, and that at a concentration of 150 parts of sulphur dioxide to one million parts of air, the air becomes unbreath. able, some idea jan be gained of the lifc of a canister even under adverse mill conditions. In addition to their use in the sulphite mill, these masks are of great assistance in the bleach room, where they are worn continuously during the mixing of the bleach liquor. Aside from monetary considerations, the , increased oomf ort and safety of the workmen is sufficient argument in favour of the addition of gas masks to the regular mill equiprnent.