892 COLLODION 



When the coke is ready to be taken from the oven, the engine and ram are placed 

 opposite to the end of the oven, and three wagons of coal are placed over the three 

 openings at the top. The coke is then pushed out by the ram, this operation occupying 

 about two minutes. A jet of water is at once applied to the coke whilst it is being 

 spread out on the floor. At the same time the lower doors are closed, and the coal 

 dropped into the oven, the apertures through which the coal passes being immediately 

 covered up by sliding doors. The coal is levelled in the ovens by means of rakes 

 passed through the opening of the upper doors. The upper doors are then closed. 

 The time occupied from the moment the doors are opened to their being sealed up 

 again is eight minutes. These ovens have been found, by a large number of experi- 

 ments to yield only 2 per cent, short of the actual quantity of fixed carbon contained 

 in the coal used. 



The workings of the ovens at Thorncliffe, Chapeltown, gave the following compara- 

 tive results : 



Per cent, of coke for Per cent, of coke 

 washed coal for unwashed coal 



Common Oven 45 . . .54 



Coppee Oven . ... 59 ... 68 



The high per-centage of carbon yielded by the Coppee oven is probably chiefly due : 

 1st. To the delicate manner in which the admittance of air to the ovens can be 

 regulated. The temperature of the common oven is comparatively low when the 

 combustion of the coal commences, and some time is occupied before the coal is in a 

 state of combustion. During this time a considerable quantity of air is allowed to 

 enter the oven, and carbonic acid is formed. This naturally takes up a large propor- 

 tion of the carbon in the coal, which is thus removed almost before the coking pro- 

 cess begins. When, however, the temperature of the oven in being refilled is very 

 high, as in the Coppee system, it is not unlikely that the free carbon, being thrown 

 off quickly, will unite with the air and form the oxide, taking up no more carbon 

 than if, by the introduction of a larger quantity of air, carbonic acid were formed. 



2nd. To the very small space allowed in the oven for the movement of the burning 



3rd. To the care with which leakages are provided against. 



The quickness with which coke is manufactured by the Copp6e system is doubtless 

 due to the rapid combustion caused by the action of the constantly-maintained high 

 temperature of the side, top, and bottom of the ovens, up the enclosed thin upright 

 layer of coal. 



Such is a sufficient general description of this new method of coking coal. For 

 further particulars as to the cost of erection, working expenses, utilisation of gases, 

 and other matters, the reader is referred to a paper read by Mr. Emerson Bainbridge 

 before the North of England Institute of Mining and Mechanical Engineers, and 

 published in their 'Transactions' 1873, p. 81. 



Messrs. Breckon and Dixon have patented a coke-oven in which the heat of the 

 ignited products of combustion is utilised by circulating through flues beneath the floor 

 of the ovens. It is said that by thus heating the floor, the process of coking is greatly 

 facilitated. 



In the so-called anchor-ovens the entire charge of coke may be drawn out in one 

 mass, by means of an iron instrument termed an anchor, thus saving a considerable 

 amount of labonr. 



COXES. A name given to tin plates which have been prepared with coke. 



COLCOTHAR OP VITRIOL (Eouge dAngleterre,~ST.; Bothes Eisenoxyd, Ger.), 

 the antiquated name of oxide of iron. It is the brownish-red peroxide of iron, pro- 

 duced by calcining sulphate of iron at a strong heat, levigating the resulting mass, 

 and elutriating it into an impalpable powder. A better way of making it, so as to 

 complete the separation of the acid, is to mix 100 parts of the green sulphate of iron 

 with 42 of common salt, to calcine the mixture, wash away the resulting sulphate of 

 soda, and levigate the residuum. The best sort of polishing powder, called jewellers' 

 rouge, or plate-powder, is the precipitated oxide of iron prepared by adding solution 

 of soda to solution of copperas, washing, drying, and calcining the powder in shallow 

 vessels with a gentle heat, till it assumes a deep brown-red colour. 



COXiD BLAST. See IKON and HOT BLAST. 



COLLIDIWE. A volatile base discovered by Anderson in bone oil, and subse- 

 quently found in shale naphtha. 



COLLODION. M. Malgaigne communicated to the French Medical Journals 

 some remarks on the preparation of gun-cotton for surgical purposes. Several French 

 chemists, at the suggestion of M. Malgaigne, attempted to make an ethereal solution of 

 this compound by pursuing the process recommended by Mr. Maynard in the American 



