Towler, John. The Silver Sunbeam. Joseph H. Ladd, New York: 1864. Electronic edition prepared from facsimile edition of Morgan and Morgan, Inc., Hastings-on-Hudson, New York. Second printing, Feb. 1974. ISBN 871000-005-9
|Commercial sulphuric acid, spec. grav., 1.843 at 60 Fahr.,.||24 fluid ounces|
|Commercial nitric acid, spec. grav., 1.457 at 60 Fahr.,.||8 fluid ounces|
|Water,||7 fluid ounces|
The vessels used in the preparation of pyroxyline may be large porcelain or glass evaporating-dishes, sitting closely in the cover of a water-bath, maintained at a temperature of 150° Fahrenheit. Each dish is furnished with a pane of glass, fitting upon it as a lid or cover. Let the water-bath be first raised to the indicated temperature; then pour the sulphuric acid into one of the dishes, add to this the water, and mix intimately by stirring with a glass rod with a rounded end; finally pour in the nitric acid, and perform the same operation to insure an intimate mixture. The temperature of this mixture will rise from 15 to 20 degrees above the point required. Remove the dish, therefore, from the bath until the temperature falls to 150°. The temperature can be lowered by stirring the mixture with cold stirring-rods or spatulas of porcelain or glass. Whilst the acids are cooling the cotton can be divided into about a dozen lots, and each lot must be gently separated into a loose condition. As soon as the proper temperature has been attained, the dish is reinstated in its position in the water-bath, and the cotton is introduced one lot at a time, so that each is carefully pressed down beneath the surface by the glass rod. As soon as all the cotton has been introduced and completely covered by the acid mixture, the lid is placed on the dish for six or eight minutes.
The thermometer used on such occasions for ascertaining the temperature of the water or mixed acids, must be strongly made, so that the bulb can be moved about in the fluid with some degree of briskness without any liability to break; it is furnished with a hinged back, which allows the lower portion to be reflected on itself, and the bulb and the lower part of the stem to be exposed. Such thermometers are manufactured for the chemist, and can be purchased at the photographic establishments.
The acids are now poured into another dish close by, allowing the largest portion to drain off, and preventing the cotton from falling out at the same time by the cover which is retained in its place. The dish containing the pyroxyline is then quickly immersed in a large tub of water, and the cotton is well stirred about so as to part with the largest portion of its acidity; it is then taken out with a pair of glass rods and plunged into fresh water in another tub, and again thoroughly washed. After this operation the pyroxyline is placed in a wooden chamber through which a current of water is kept running for twenty-four hours or more, or at least until every trace of acidity has been removed. During this time the agglutinated or adherent portions are carefully separated, so that the stream of water can more easily act upon each fiber. When blue litmus paper is no longer turned red by the water as it proceeds from the cotton, the latter is taken out, again carefully separated and placed in thin patches on sheets of paper in the sun to dry; or it may be dried on zinc plates, being part of a hot-water bath, whose temperature is maintained at about 120° Fahrenheit. At this temperature pyroxyline will not explode. In the hot days of summer, however, it can be dried quite efficaciously when placed out in the sun.
Pyroxyline, when exposed to the air, absorbs moisture; it undergoes decomposition, too, in an air-tight vessel, if light reaches it; the products of decomposition being nitric acid, peroxide of nitrogen, and probably other compounds. It has not yet been thoroughly ascertained by what means it can be preserved in a normal condition permanently; absence of moisture and of light have been found to assist in this preservation.
If a specimen of pyroxyline by keeping manifests an acid reaction, it is advisable to wash the cotton in several waters, as before, and again to dry it. To neutralize the cotton by an alkali, or a carbonated alkali, is scarcely to be recommended, because they both have a tendency to decompose it; and especially if any trace of these should be left in the fiber, decomposition is likely to ensue in the drying.
No. 2. Formula for the Preparation of Pyroxyline.
|Commercial sulphuric acid, spec. grav., 1.843, at 60° Fahr.,.||18 ounces,|
|Commercial nitric acid, spec. grav., 1.43, at 60° Fahr.,.||14 ounces|
Proceed with these ingredients in all other respects as with those in Formula No. 1.
No. 3. Formula for the Preparation of Pyroxyline.
|Commercial sulphuric acid,||40 ounces,|
|Pure nitrate of potassa,||20 ounces|
As soon as the mixture of acid and nitre has been thoroughly mixed, and almost cool, the cotton is introduced in small portions and well stirred. In about a quarter of au hour the whole mixture is thrown into a large tub full of water; in this way the pyroxyline is freed as much as possible from the acid; after this it is washed in warm water, and finally in a running stream, as in Formula No. 1.
No. 4. Formula for the Preparation of
|Sulphuric acid,||4000 grains.|
|Pulverized pure nitrate of potassa,||2000 grains|
Place these in a glass vessel provided with a close-fitting cover, and stir them intimately together with a glass rod. Next add 150 grains of fine cotton-wool, in small flocks at a time, and immerse them thoroughly with the glass rod. When all the cotton has been introduced, close the vessel and set it aside for ten or fifteen minutes. After this, the pyroxyline is withdrawn by means of a pair of glass rods, and well washed, as before recommended, and dried.
In all these formulas the acids, when once used, can not be employed a second time; by distillation, the nitric acid that has not been decomposed might be obtained and used over again, if other combinations and decompositions did not result from the application of so high a temperature. In general the mixture is regarded as useless, and thrown away.
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