By Dr. BOWMAN.
Every chemist knows that cotton is chiefly composed of cellulose, CHO, with some other substances in smaller quantities. This, although the usual opinion, is only true in a partial sense, as the author found on investigating samples of cotton from various sources. Thus, while mere cellulose contains carbon 44.44 per cent. and hydrogen 6.173, he found in Surat cotton 7.6 per cent. of hydrogen, in American cotton 6.3 per cent., and in Egyptian cotton 7.2 per cent. The fact is that along with cellulose in ordinary cotton there are a number of celluloid bodies derived from the inspissated juices of the cotton plant.
In order to gain information on this subject, the author has grown cotton under glass, and analyzed it at various stages of its life history. In the early stage of unripeness he has found an astringent substance in the fiber. This substance disappears as the plant ripens, and seems to closely resemble some forms of tannin. Doubtless the presence of this body in cotton put upon the market in an unripe condition may account for certain dark stains sometimes appearing in the finished calicoes. The tannin matter forms dark stains with any compound or salt of iron, and is a great bugbear to the manufacturer. Some years ago there was quite a panic because of the prevalence of these stains, and people in Yorkshire began to think the spinners were using some new or inferior kind of oil. Dr. Bowman made inquiries, and found that in Egypt during that year the season had been very foggy and unfavorable to the ripening of the cotton, and it seemed probable that these tannin-like matters were present in the fiber, and led to the disastrous results.
Although the hydrogen and oxygen present in pure cellulose are in the same relative proportions as in water, they do not exist as water in the compound. There is, however, in cotton a certain amount of water present in a state of loose combination with the cellulose, and the celluloid bodies previously referred to appear to contain water similarly combined, but in greater proportion. Oxycellulose is another body present in the cotton fiber. It is a triple cellulose, in which four atoms of hydrogen are replaced by one atom of oxygen, and like cellulose forms nitro compounds analogous to nitro glycerine. It is probable that the presence of this oxycellulose has a marked influence upon the behavior of cotton, especially with dye matters. The earthy substances in cotton are also of importance. These are potassium carbonate, chloride, and sulphate, with similar sodium salts, and these vary in different samples of cotton, and possibly influence its properties to some extent. Then there are oily matters in the young fiber which, upon its ripening, become the waxy matter which Dr. Schunk has investigated. Resin also is present, and having a high melting point is not removed by the manipulative processes that cotton is subjected to.
When this is in excessive amount, it comes to the surface of the goods after dyeing.