HOW RADIUM IS BOUGHT

Dominion, Volume 22, Issue 92, 12 January 1929, Page 24

HOW RADIUM IS BOUGHT

A GRAMME THAT IS NOT WEIGHED Buying a gramme of radium, even if you have the necessary money, is by no means such a simple matter as the purchase of a £12,000 pearl necklace, though the cost is about equal. In the first place it is not weighed.Its value depends upon its “radioactivity,” and this must be measured. This delicate task is always entrusted to some impartial scientific institution, such as the National Physical Laboratory. A sensitive instrument known as an electroscope, which reacts to the gamma rays of radium, is used. It is surrounded by lead screens, which shut out all other rays, and by comparing the effect of the sample to be measured with a standard amount placed at the same distance, its quantity can be calculated to within one-hundredth of a milligramme. A still more delicate test, the “emanation method," will detect and measure the presence of radium in ores or minerals in amounts of 1-100,000,000,000 of a milligramme, but is not necessary for practical purposes. The few rains qf sandy, brownish powder, which are all that appears to the naked eye in a sample of radium sulphate worth many thousands of pounds, cannot,'for obvious reasons, be allowed to be about loose. They are hermetically enclosed with gold solder in platinum containers. These may be of many different shapes or sizes, according to the clinical purpose for which they are required, and are usually made to the specification of the purchaser. Some are very much like an ordinary sewing needle,- either blunt-ended or with a sharp triangular point to enable them to be buried deep- in malignant growths. A tiny cavity, like the bore of a rifle-barrel, runs down the centre of them as a receptacle for the radium. An eye at the outer end, through which a thread can be minimises the risk of loss. For surface application, flat containers fitted with brass, silver, or aluminium filters, by which those rays which are not wanted are absorbed, are used. Very small quantities are sometimes sealed into tiny platinum cylinders, and a varying number of these can be placed, as required, into a silvergilt outer tube, or into the hollow of an empty platinum needle. Although the making of these delicate containers necessarily takes some little time, there is no undue delay once the customer has made up his mind upon what type and size will best suit his special requirements.

A small amount of radium is mined in Australia, but the bulk, of it comes from the Belgian Congo, which it is found in pitch-blende ores, in company with cobalt, copper, and other metals. The mines in Colorado, owing to their small content, cannot now be worked at a profit.