Part 6 (1/2)
Theoretically,[A] therefore, 1 part of cellulose should forun-cotton Practically, however, this is never obtained, and 16 lb fro The enerally 1 to 3, or 25 per cent nitric acid to 75 per cent sulphuric acid
[Footnote A: (594 x 1)/324= 183]
[Illustration: FIG 11--TANK FOR DIPPING COTTON]
[Illustration: FIG 12--THE COOLING PITS]
The dipping is done in cast-iron tanks (Fig 11), a series of which is arranged in a row, and cooled by a streaallons, and the cotton is dipped in portions of 1 lb at a time It is thrown into the acids, and the workman moves it about for about three minutes with an iron rabble At the end of that ti, just above the acids, fixed at the back of the tank, where by ently squeezes it, until it contains about ten tihs 10 lbs) It is then transferred to earthenware pots to steep
[Illustration: FIG 13--COTTON STEEPING POT]
~Steeping~--The nitrated cotton, ithdrawn fro an excess of acids, is put into earthenware pots of the shape shown in Figs 12 and 13 The lid is put on, and the pots placed in rows in large cooling pits, about a foot deep, through which a strea These pits for house The cotton reht hours, and hest temperature desirable, but the cooler the pots are kept the better At the end of forty-eight hours the chemical reaction is complete, and the cotton is or should be wholly converted into nitro-cellulose; that is, there should be no unnitrated cotton
[Illustration: FIG 14--HYDRO-EXTRACTOR]
~Whirling Out the Acid~--The next operation is to re the contents of two or three or1,000 to 1,500 revolutions per minute The hydro-extractor consists of a machine with both an inner cylinder and an outer one, both revolving in concert and driving outwardly the liquid to the chae pipe The wet cotton is placed around the inner cone The cotton, when dry, is ree tank of water, and the waste acids are collected in a tank[A]
[Footnote A: Care un-cotton does not fire, as it does sooes to remove it after the machine is stopped It occurs more often in damp weather Dr Schupphaus, of Brooklyn, USA, proposes to treat the waste acids fro to them sulphuric anhydride and nitric acid The sulphuric anhydride added converts the water liberated fro~--The cotton has now to be carefully washed This is done in a large wooden tank filled ater If, however, a river or canal runs through the works, a series of wooden tanks, the sides and bottoms of which are pierced with holes, so as to allow of the free circulation of water, should be sunk into a wooden platfors the surface of the river in such a way that the tanks are i the time that the cotton is in the water a workman turns it over constantly with a wooden paddle A stream of water, in the form of a cascade, should be allowed to fall into these tanks The cottonsoht, at once carries the cotton beneath the surface of the water This proceeding is necessary because the cotton still retains a large excess of strong acids, and when ives rise to considerable heat, especially if mixed sloater After the cotton has been ashed, it is again wrung out in a centrifugal machine, and afterwards allowed to steep in water for some time
[Illustration: FIG 15_a_--THE BEATER FOR GUN-COTTON]
~Boiling~--The washed cotton is put into large iron boilers with plenty of water, and boiled for some time at 100 C In some works lead-lined tanks are used, into which a steam pipe is led The soluble impurities of unstable character, to which Sir FA Abel traced the liability of gun- cotton to instability, are thereby removed These impurities consist of the products formed by the action of nitric acid on the fatty and resinous substances contained in the cotton fibres The water in the tanks should be every now and again renewed, and after the first few boilings the water should be tested with liter found to be acid
[Illustration: FIG 15_b_--WHEEL OF BEATER]
~Pulping~--The idea of pulping is also due to Abel By its means a very much more uniform material is obtained The process is carried out in an apparatus known as a ”Beater” or ”Hollander” (Fig 15, _a, b_) It consists of a kind of wooden tank so shape, in which a wheel carrying a series of knives issloped up so as to al wheels This part of the floor, known as the ”craw,” is a solid piece of oak, and a box of knives is fixed into it, against which the knives in the revolving wheel are pressed The beater is divided into two parts--the working side, in which the cotton is cut and torn between the knife edges in the revolving cylinder and those in the box; and the running side, into which the cotton passes after passing under the cylinder The wheel is generally boxed in to prevent the cotton fro its revolution The cotton is thus in constantbetween the knives in the revolving cylinder and those in the box fixed in the wooden block beneath it The beater is kept full of water, and the cotton is gradually reduced to a condition of pulp The wheel revolves at the rate of 100 to 150 times a minute
[Illustration: FIG 16_a_--POACHER FOR WAshi+NG GUN-COTTON]
[Illustration: FIG 16_b_--PLAN OF THE POACHER]
[Illustration: FIG 16_c_--ANOTHER FORM OF POACHER]
When the gun-cotton is judged to be sufficiently fine, the contents of the beater are run into another very si 16, _a, b, c_), in which the gun-cotton is continuously agitated together with a large quantity of water, which can be easily run off and replaced as often as required When the material is first run into the poacher from the beater, the water hich it is then mixed is first run away and clean water added The paddle wheel is then set in motion, and at intervals fresh water is added There is a strainer at the bottom of the poacher which enables the water to be drawn off without disturbing the cotton pulp After the gun-cotton has been in the poacher for soe mesh sieve in the current for a h and partly be caught upon the sieve, and an average sample will be thus obtained The sample is squeezed out by hand, bottled, and taken to the laboratory to be tested by the heat test for purity It first, however, requires to be dried This is best done by placing the sa it under a hand-screw press, where it can be subjected to a tolerably severe pressure for about three minutes It is then rubbed up very finely with the hands, and placed upon a paper tray, about 6 inches by 4-1/2 inches, which is then placed inside a water oven upon a shelf of coarse wire gauze, the te kept as near as possible to 120 F (49 C), the gauze shelves in the oven being kept about 3 inches apart The sample is allowed to remain at rest for fifteen minutes in the oven, the door of which is left wide open After the lapse of fifteen minutes the tray is removed and exposed to the air of the laboratory (away fro at some point within that time rubbed upon the tray with the hand, in order to reduce it to a fine and uniforre 249)
If the gun-cotton sample removed from the poacher stands the heat test satisfactorily, the machine is stopped, and the water drained off The cotton is allowed so out byThe poachers hold about 2,000 lbs of material, and as this represents the products ofoperations, a very uniform mixture is obtained
Two per cent of carbonate of soda is sometimes added, but it is not really necessary if the cotton has been properly washed
~Coun-cotton, in the state in which it is removed from the poacher, contains from 28 to 30 per cent of water In order to remove this, the cotton has to be coun-cotton is packed in boxes containing 2,500 lbs of dry material In order to ascertain how much of the wet cotton must be put into the press, it is necessary to deter 2,000 grains upon a paper tray (previously dried at 100 C) in the water oven at 100 C for three hours, and re-weighing and calculating the percentage of water It is then easy to calculate how un-cotton must be placed in the hopper of the press in order to obtain a block of coht Various forun-cotton is sent out either as solid blocks, compressed discs, or in the forht cases The discs are often soaked in water after compression until they have absorbed 25 per cent of moisture
[Illustration: FIG 17--OLD METHOD 100 PIECES]
[Illustration: FIG 18--NEW METHOD ONE SOLID BLOCK]
At the New Explosives Coun-cotton are pressed up under a new process, whereby blocks of gun- cotton, for use in sube charges of coun-cotton have hitherto been built up fro 17), as it has been ies in a proper un-cotton was the invention of Mr A