QUANTITATIVE ANALYSIS BY MEANS OF THE MICROSCOPE 211 
may be made it is essential that the globules of metallic mercury 
shall never be so large that they become flattened and thus not 
perfect spheres. In determining the diameter of the spheres 
proceed exactly as described above, always making several 
measurements of the sphere diameters. From the average of 
the data thus obtained, calculate the weight W = (# X 0.5236) 
X 13 - 59 - 
In estimating the percentage of the different fibers entering 
into the composition of a given sample of paper, it is customary 
in most commercial paper-testing laboratories to guess at the 
per cent of a given fiber without comparison with standards and 
without counting the fibers, the usual practice being for several 
analysts to “ guess ” at the comppsition independently. These 
men in time become very expert and their findings will generally 
check within i per cent. In the opinion of the author, com¬ 
paring with known standards, using the comparison microscope 
or comparison eyepiece is quicker and gives a more reliable 
approximation.' 
Herzog ^ has suggested a microscopic method for the quan¬ 
titative estimation of the different fibers in fabrics, or for the 
per cent of different colored fibers in a fabric. Stated briefly, 
the process is as follows: A tiny piece of the fabric is imbedded 
in paraffin (M.P. 60°) by repeated dipping. After cooling, 
sections about o.i to 0.2 millimeter are cut by means of a razor 
or microtome knife. One of the sections is transferred to an 
object slide, warmed until the paraffin melts and is tipped back 
and forth to evenly distribute the fiber fragments. A drop 
of balsam is placed upon a cover glass and lowered upon the 
preparation. The entire number of each different fiber is then 
ascertained by counting, using a net eyepiece micrometer. 
Having thus found the relative proportion of the fibers, their 
absolute size is next determined by measurements of length 
and thickness, or since the thickness of the section cut is 
known and the average diameter of different fibers is also well 
established, actual dimensional measurements may not be re¬ 
quired. The weight is calculated by multiplying the absolute 
1 Herzog, Z. Chem. Ind. KoL, I (1907), 202. Z. Text. Ind., 1906, No. 4. 
