Document reLdNvXJ5NXXM6n3xapDMBYv0

-65- alxing operation is 1,003,337 partioles, less than ten microns, per cubic foot of air. These partioles are all slightly angular, crystalline in appearance under the Konlmeter microscope and about five microns in else. Many are transparent, glass like. There are a- number of small black specks. H - TALC or ''SOAPSTONE": Pulverised talc or "soapstone" is used as a filler in the manufacture of "hot neck" greases used in the steel mills. According to R. B. Ladoo (U.S. Bureau of Mines Bui. No. 213, 1919) ordinary talc or soapstone is Steatite (hydrous magnesium silicate - H2Mg3(8103)4). In the form of powder, the talc is greyish white. Associate Chemist Frederick Goldman of the U.S, Bureau of Mines, who made a chemical analysis of samples of talc as marketed, reports1 Si02............................ 46,04 per cent CaO............................. 4.39 " " KgO.............................. 26.20 " " Combined Oxides.. s.. 15.64 " " Grease makers usually consider the composition of "soapstone" which they use as aj^ proximately 90$ magnesium silicate and 10$ calcium carbonate. It comes in 90-pound paper bags, 700 bags to a box car. About 7200 pounds are used per batch and one batch is made a day on an average. The "soapstone" is dumped into the mixing kettle by two men with an average service of ten years. This dumping vfaich requires about an hour per batch is a rather dusty operation. One sample taken at face level just after a bag had been dumped had as high as 22,995,840 particles, ten microns orless in site, per cubic foot of air. The average dust produced was 13,064,960 dust par ticles per cubic foot. About 98$ of these dust particles were transparent, crystal line, irregularly shaped plates and rods, in appearance under the Konimeter micro scope. Most of these particles (about 98$) were five microns or less in size, the remainder being ten microns or over; about 2$ were scale-like, semi-opaque, five mi crons or less in size. Physiological Effects Produced By Talo Dusts. About two years ago Dr, W. C. Dreessen, Passed Assistant Surgeon, and J. M. Dalla Valle, Assistant Sanitary Engi neer, United States Public Health Service, made a study to ascertain whether there is a connection between talc dust exposure and the relatively high tuberculosis death rate in Murray County, Georgia, where two talc mills and mines are located. They found (Reprint No. 1669 from the Public Health Reports .Vol. 50, No. 5, Feb. 1, 1935, pages 131-143)* "Physical and roentgenologic examinations were made of 66 men and women who were exposed or had been exposed to talc dust. In the higher dust groups comprising S3 men, 8 were found to have Pneumo coniosis I and 8 to have Pneumoconiosis II or III. Six of the thirteen examined were diagnosed as having Pneumoconiosis I. No advanced stages of the disease were found in this group. In the group exposed to low concentrations of dust, no Pneumoconiosis was found." The final oonclusion of this study was that although Georgia talo appears to be "more injurious than tremolite talc" the high tuberculosis mortality rate in the County "oould not be attributed to the tale industry". Investigators have suggested, however, that for more or less continuous expo sures concentrations of talc or "soapstone" dust should not exceed 15,000,000 par ticles, ten microns or less in site, per cubic foot of air. _I_ - GRAPHITE: Powdered graphite (80$ to 85$ graphitic carbon and 15$ probably magnesium silicate) is used in the manufacture of spring and pressure lubricants. It EMO0154 5