Poison Detector

Many an employe, going about his tasks in a manufactory where mercury heating is in process, has found himself suffering unaccustomed ailments. His eyes glaze with fever. Dysentery sets in. The dentist cautions him against pyorrhea, for his teeth are loosening. Finally the doctor orders him to give up work for a long vacation in the country and he recovers. What has occurred in such cases is an insidious mercurial poisoning, the result of inhaling mercury vapors escaped from leaking seams in the apparatus. The illness may be a long time coming or a short time. Mercury is cumulative in effect, depending almost entirely upon the quantity of poison absorbed, very little upon the time of absorption.

Scientists in the General Electric Co. laboratories have invented an instrument to register the presence of as little as one part of mercury in 20,000,000 parts of atmosphere. Before the poison is detected by symptoms of illness in drooping employes, a coating of yellow sulphide on a strip of paper gives the signal by turning black (the result of contact between selenium sulphide and mercury). The degree of blackness is photographed by shining a light through the strip of yellow sulphide. If the sulphide has turned dark, less light will penetrate; if black, no light will penetrate. This is recorded on an ammeter legible to every eye.