THE EAGLE EYE.

Ashburton Guardian, Volume XLV, Issue 10350, 13 March 1925, Page 2

THE EAGLE EYE.

ON UNREAL SILK AND JAM

DETECTION BY MICROSCOPE. Professor J. C. Sperrin-Johnson, of the Auckland University, addressed the Wellington Rotary Club the other day on “ The Microscope in Commerce. * Professor Sperrin-Johnson said that one of the great fundamentals of modern life was commerce, and m commerce the microscope had many uses. The microscope was a system of lenses, and the first one used was invented by Gallileo, the astronomer. That microscope was so primitive that we laughed at it to-day, but ever since the early seventeenth century improvements had been effected, 10-day the microscope was a wonderful instrument. Its uses, apart from a delightful hobby, included the revealing of the composition of rocks, of plants, the adulteration of food and drugs, and other materials used in commerce, and last, hut not least, the microscope was a wonderful help in elucidating crime. To our microscopical technique we could attach the camera and no trained persons could quarrel as to the pictures they saw. Speaking of the application of the microscope to the textile _ industry. Professor Sperrin-Johnson said that it might be thought that apart from pretty dresses and that sort of thing this was rather prosaic, but it was a really fascinating subject. The analytic powers of the microscope could be applied to discover various adulterations. Under the microscope various kinds' of wool could be distinguished from one another, and there was not the slightest chance of there being any doubt about them. Another textile of animal origin was silk, which came from the mouth of the caterpillar. Under the microscope the characteristic appearance of .silk was utterly different from that of wool.

Real and other Silks. Suppose one bought a material which was supposed to be pure silk and was not. Tease a portion of it and put it under the microscope, and the slightest trace of cotton, jute, artificial silk, or any other material would bo at once distinguished from the silk. There were very few of the articles sold as silk—unless specially guaranteed—that really were silkworm silk. Many were adulterations of silk. It would he almost impossible to tell the difference by the feel, but with a microscope there would be no doubt. The real silk was transparent and had a certain coating. The artificial silk was a plant product, and ho thought it a wonderful product. To the naked eye it appeared to be similar to the real thing, but under the microscope it would be found that the producers had been unable to give it the coating by which the real silk could be distinguished. The slightest dilution could be discovered. Wool never had been synthetically produced. It was too complicated. Chemists cannot make Starch. Professor Sperrin-Johnson touched interestingly on the> adulteration of food and drugs. Synthetic chemists, he said, had done marvels in all departments of their work, but brilliant a» their exploits were, starch had never been made by a chemist, so if we found it in any material we knew it was of vegetable origin. Face powder was supposed to be rice starch. If one tried to use potato starch as face powder it would be rather patchy. The differences between the various vegetable starches were easily seen through the microscope.

Wood Pips in Jam.. Take the case of jam. Any foreign vegetable pulp in jam could be detected easily. If one bought raspberry or plum jam, it would aid the aesthetic taste to have the right colour with the right kind of pips. He believed people in Liverpool used to make a living producing artificial plum stones and raspberry pips from wood. These used to be put into jams which were camouflaged as the better class of jams. Such adulterations could be at once detected with the aid of the microscope. An American writer had classified jams into two. great groups—sophisticated and unsophisticated. The sophisticated contained materials that should not have been there. Because of the certainty with which it revealed adulterations, the photo-micograph was of great importance in legal proceedings.