. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. the scientific ac-curacy of true measurement under the microscope, it has theadvantage of permitting a rapid observation of a large number offibers, and a trained analyst can thus test a very large number ofsamples in a day and obtain a true valuation of the quality ofthe pulp tested. Mechanical wood pulp, as might be expected,gives greater variation as to length and coarseness of fiber thanany other kind of pulp; this will be evident from examination ofthe six photomicrographs shown in Fig. 16. The circle
. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. the scientific ac-curacy of true measurement under the microscope, it has theadvantage of permitting a rapid observation of a large number offibers, and a trained analyst can thus test a very large number ofsamples in a day and obtain a true valuation of the quality ofthe pulp tested. Mechanical wood pulp, as might be expected,gives greater variation as to length and coarseness of fiber thanany other kind of pulp; this will be evident from examination ofthe six photomicrographs shown in Fig. 16. The circles herereproduced may be ten times as large, or even larger, whenthrown on the screen, as those shown in the illustration, depend-ing on the adjustments of the lantern, and the sizes of the fiberswill be changed in the same proportion. This procedure hasdisadvantages, in that the stock assumes a different appearancewhen dried, and that the sample is very small. 52. Blue-glass Test.—Another test for comparing the lengthand coarseness of fibers, generally used for a mill-control test. ^iffcficpX-X *x Fig. 17. for uniformity in the manufacture of ground-wood pulp, iswhat is known as the blue-glass test, which may be describedas follows: Referring to Fig. 17, the apparatus consists essentially of aframe B, which contains three or more trays A having clear 32 REFINING AND TESTING OF PlLP §S glass bottoms I, a box F through which the frame slides, anelectric light C, a tin reflector D, a magnifying glass E, and ashade H. A circular hole, about 3^ inches in diameter, overwhich the magnifying glass is placed, is cut in the top of the underneath this hole, a piece of blue glass G is sunk intothe bottom of the frame. A piece of ground glass J is placedbetween the light C and the examining chamber K, for the pur-pose of diffusing the light from the bulb C. To operate, verydilute stock is poured on the glass trays, which are moved alongunder the magnifying glass. The stock i
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpaperma, bookyear1921
