Science Siftings

New Zealand Tablet, 30 September 1915, Page 47

Science Siftings

By ‘ Volt.’

Invisible Ink. Invisible ink, which figured in the recent espionage trial, appears to have been known since the early days of . writing, for both Ovid and Pliny give recipes for the preparation of such a fluid, the one from milk, the other from various vegetable juices. In the middle ages many writers mention ‘ magnetic 5 and ‘ magic ’ inks, the action of which some of them averred to be miraculous. To-day such fluids are technically known as sympathetic inks, and there are numerous patents for their manufacture. White-washed Kerbstones. Since the exigencies of war have made it necessary largely to eliminate street lighting in British cities, it has been found, advisable in certain instances to whitewash the kerbs on either side of public thoroughfares so as to make it easier to discern the roadways at night. At Norwich a pneumatic painting-machine carried on a steam waggon has been successfully employed for doing this work. The lime solution is forced through a hose under air-pressure and directed at the kerb. A nozzle especially designed so as to prevent the spreading of the wash beyond certain limits is used. With this equipment the work can be done at Tate of about three miles an hour. Nitrate or Saltpetre. Mr. Herbert Mansfield, B.Sc., F.J.1., writing in the Daily Chronicle, says that few people realise the debt we owe to Chili. For years past she has supplied the whole world with sodium nitrate or 1 Chili saltpetre/ as it is called, a substance which under modern agricultural methods is rapidly becoming indispensable as a manure to the farmer, while at the same time it is the source from which we obtain nitric acid, the basis of practically every high explosive. Chili cannot continue supplying the world with 2,000,000 tons of nitrates every year for an unlimited period. And scientists have for long been anxiously seeking for another source of supply. It is calculated that the resources of Chili will be exhausted by 1923. There is plenty of nitrogen and oxygen in atmospheric air, and the problem which had to be solved was how to make them combine to form nitric oxide, from which nitrates and nitrites could be obtained. Radium and Agriculture. A series of remarkably interesting experiments have been recently carried out in the West of England by certain scientists to demonstrate the extraordinary effect on vegetable growth produced by the addition to the soil of radium-bearing and radio-active materials. It appears that radishes and other root crops are obtained nearly five times as large as those grown in untreated soil at the same time. If this process could be generally adopted by our agriculturists the increase in the prosperity of the nation would be very large. The initial cost of such a system has hitherto stood in the way of its general adoption. But the recent discovery by MM. Detaille and Lafayaise, the two distinguished French chemists of Paris, and Professor Scammell, M.5.C.1., of Hadleigh, Essex, that coal contains radium, which, in the form of ‘ lignaite,’ can be used for the radiumization of the soil, places the process within the reach of evtfry agriculturist in the country. Fruits, flowers, and vegetables can be grown in a much shorter time, in much larger quantities, and of finer quality by the use of ‘ lignaite,’ the cost of the treatment of an ordinary sized garden being very trifling.