Document 10aLbraLjvqRemdrm57bmZpYo

a- 208 FRANK A. PATTY SAMPLING AND ANALYSIS OP CONTAMINANTS 209 therefore any petrographic method applied to them must depend largely, if4'! r-BncrosfuijLQn^the amount of that substance in the sample. Quartz has four lines entirely, upon refractive indices. Such methods08 do not differentiate bet^fl intense for quantitative measurement. By the use of an quartz and other minerals of the same or similar refractive index, such as feldspars, mica, talc, and some other minerals frequently found associate<C|i!l * - \ ' ar>d a microphotometer for measuring the relative density of unknown and those of the internal standard, quantitative measure- quartz. They are intended to be rough estimates only, and give a maximum .yjpf ^^u^ii^tilfhotory accuracy may be obtained.06 For good results, samples for rather than .a true quartz value. However, in many situations a knowledge-oSffi ^R'j(^ljji^t^|efcground to 200 mesh or smaller, and after the internal standard composition of the minerals from which the dust was generated can be tilt (i^d^'V^alieflythe sample must be further ground and mixed. A special type of advantageously and can give the maximum estimate the status of a true liHfl by ruling out any interfering minerals in the same refractive index range tF'* known not to be present. ""Ni using methanol as a dispersing agent, has been used for : hours. has been the advantageous use of Geiger counter By X-ray Diffraction. Where all of the dust particles are less than 5&BI diameter, the only successful means so far devised of determining the crystalll p^cctp grs^ifor- determining the densities of the lines in the diffraction pattern, in some instances of partial overlapping of lines, and, in free silica content is by means of x-ray diffraction. When x-rays strike an otifi `.''.iliviSitingthe need for an internal standard. some of the rays are diffracted. If the x-rays are monochromatic and a beam parallel rays is directed at a finely powdered pure material, this diffraction;1^ sumes a characteristic and reproducible pattern that can be registered as lineif a photographic film (Figure 11). The rays that pass directly through the pb&i| BACTEmA AND OTHER MICROORGANISMS ^ilv'y^aniphng and evaluation of microorganisms in the atmosphere have yvuilW'iMBflttention in recent years, but the procedures are still in an experi- '.'There are several collection methods that employ the principle of ''T^jf^^Mufch as the air centrifuge,70 the funnel device,71 the slit impinger,12 sampler,78 the sieve device,74 and the exposed agar ^^^^iish method. Simple Folin scrubbers,73 beaded scrubbers,76 and Sii^ffifpPl>ferBTT have also been used, and they give much higher results than `Tr- ^J.jj.l'eJT'.collect the micFo"drganisms` on" a~ sblid~eurfacel The size of the Sftheir tendency to form clusters or clumps have an important bear- |fa|iye collection efficiency of a method. With the scrubbing devices flfelusters are broken up, whereas they may register as one colony lent: Discussions of -these devices including a comparison of their been published.78 ' TsmlJmg media79 have a still greater influence upon results, not only as rd,,3J"p'JHS^SWS&-^r Bgalflac'r,d, H. I. Oshry and H. H. Schrenk, U. S. Bur. Mine,s Rept. Invest. No. 3520, Figure 11. X-ray diffraction patterns of (a) quartz in dolomite, (b) ;'pufS^fi,irc;,^ut| ___________ dutHtance, proviclq a reference mark. Thisi same material; vvhiier in or mixed-with other; matter, will reproduce the same pattern even thoug^P^* other lines may be produced by other constituents in the mixture. The*flW tKen serves as a MiaBjeu3wtTficTion7wH'icF'isThbugfitl,o"depend'upbn structure.67 The density of the lines in the diffraction pattern of any sij^S* "H. L. Boss and F; W. Sehl, Ind.Eng. Chem,, Anal. Ed., 7, 30 (1935). W. D. FSstffl H. H. Schrenk, U. S. Bur. Mines Kept. Invest. No. 3868, 1938. ' '9. "J. D. Hanolvalt, H. W. Rinn and L. K. Freval, Ind. Eng. Chem., Anal. Ed., lSl (1938). -M " and H. H. Schrenk, V. S. Bur. Mines Rept. Invest. No. 3888, 1946. J. Pub. Health, 23, 58 (1933). L^iL^Kigrdna-j. .......... 3^t^fe^praiiibn, O. M. Lidwell, and J. C. Thomas, J. Hyg., 41, 197. (1941). A. Hollaender, B. Caminita, R. W. Kolb, H. F. Fraser, H. du Buy, P. A _ jsenblum, Am. J. Hyg., 40, 136 (1944). , \,t|-' - 1 ,r"" (dj^Buy_and L. R. Crisp, U. S. Pub. Health Repts., 59, 829 (1944). aaKaiipjijg7. TMed'i'Resedrch, 22,- 461 (-1-9-1--0-). Toley, and T. D. Jones, Science, 94, 445 (1941). T. T, Puck, and H. M. Lemon, Science, 97, 51 (1943). |$uy, A. Hollaender, and M. D. Lackey, U. S. Pub. Health Repts., Supplement - N sM. Frobisher, Jr., The Fundamentals oi Bacteriology. 4th ed., Saunders ^^lier' Jtft: * * ' Dunn, and B. H. Caminita, U. S. Pub. Health Repts., 60, 789 (1945). !Us 3 -w- ,