Scientific American Supplement, No. 821 | Page 5

understood the horny substance
resembling hair, with the difference that the former has no marrowy
tissue. The covering pellicle of the wool fiber consists of flat, mostly
elongated leaves, with more or less corners, lying over each other like
scales, which makes the surface of the fiber rough; this condition,
together with the inclination of curling, renders it capable of felting
readily. Pure wool consists of a horny substance, containing both

nitrogen and sulphur, and dissolves in a potash solution. In a clean
condition, the wool contains from 0.3 to 0.5 per cent. of ash. It is very
hygroscopical, and under ordinary circumstances it contains from 13 to
16 per cent. humidity, in dry air from 7 to 11 per cent., which can be
entirely expelled at a temperature of from 226 to 230 degrees
Fahrenheit. Wool when ignited does not burn with a bright flame, as
vegetable fiber does, but consumes with a feeble smouldering glow,
soon extinguishes, spreading a disagreeable pungent vapor, as of
burning horn. By placing a test tube with a solution of five parts caustic
potash in 100 parts water, a mixture of vegetable fibers and wool fibers,
the latter dissolve if the fluid is brought to boiling above an alcohol
flame, while the cotton and linen fibers remain intact.
The solubility of the woolen fibers in potash lye is a ready means of
ascertaining the percentage of wool fiber in the paper. An exhaustive
analysis of the latter can be performed in the following manner: A
known quantity of the paper is slowly dried in a drying apparatus at
temperature of 230° Fahrenheit, until a sample weighed on a scale
remains constant. The loss of weight indicates the degree of humidity.
To determine the ash percentage, the sample is placed in a platinum
crucible, and held over a lamp until all the organic matter is burned out
and the ash has assumed a light color. The cold ash is then moistened
with a carbonate of ammonia solution, and the crucible again exposed
until it is dark red; the weight of the ash is then taken. To determine the
percentage of wool, a sample of the paper is dried at 230° Fahrenheit
and weighed, boiled in a porcelain dish in potash lye 12° B. strong, and
frequently stirred with a glass rod. The wool fiber soon dissolves in the
potash lye, while the vegetable fiber remains unaltered. The pulpy mass
resulting is placed upon a filter, dried at 212° Fahrenheit, and after the
potash lye has dripped off, the residue, consisting of vegetable fiber and
earthy ash ingredients, is washed until the water ceases to dissolve
anything. The residue dried at 212° Fahrenheit is weighed with a filter,
after which that of the latter is deducted. The loss of weight
experienced is essentially equal to the loss of the wool fiber. If the
filtrate is saturated with hydrochloric acid, the dissolved wool fiber
separates again, and after having been collected upon a weighed filter,
it may be weighed and the quantity ascertained.
The weight of the mineral substances in the raw paper is ascertained by

analyzing the ash in a manner similar to that above described. The
several constituents of the ash and the mineral added to the raw paper
are ascertained as follows: Sufficient of the paper is calcined in the
manner described; a known quantity of the ash is weighed and thrown
into a small porcelain dish containing a little distilled water and an
excess of chemically pure hydrochloric acid. In this solution are
dissolved the carbonates, carbonate of lime, carbonate of magnesia, a
little of sulphate of alumina, as well as metallic oxides, while silicate of
magnesia, silicic acid, sulphate of lime (gypsum) remain undissolved.
The substance is heated until the water and excess of free hydrochloric
acid have been driven off; it is then moistened with a little hydrochloric
acid, diluted with distilled water and heated. The undissolved residue is
by filtering separated from the dissolved, the filter washed with
distilled water, and the wash water added to the filtrate. The
undissolved residue is dried, and after the filter has also been burned in
due manner and the ash added, the weight is ascertained. It consists of
clay, sand, silicic acid and gypsum.
The filtrate is then poured into a cylinder capable of holding 100 cubic
centimeters, and furnished with a scale; sufficient distilled water is then
added until the well-shaken fluid measures precisely 100 cubic
centimeters. By means of this measuring instrument, the filtrate is then
divided into two equal portions. One of these parts is in a beaker glass
over-saturated with chemically pure chloride of ammonia, whereby any
iron of oxide present and a little dissolved alumina fall down as deposit.
The precipitate is separated by filtering, washed, dried at 212°