Such are the different processes at present follow ed by the practical bleachers in Great Britain. After each of them, whether boiling or bucking in an alka line solution, immersion in oxymuriate of lime, or steeping in sulphuric acid, the goods must be care fully washed in pure water, either by machinery or otherwise, till all the materials employed are com pletely washed out of them. Upon this much of the economy and success of bleaching depends. It is likewise of great advantage to free the goods from the water which they contain after each washing, be fore subjecting them to the next operation. For this purpose, Bramah's press is employed in almost all the large bleaching-houses, and constitutes one of the greatest improvements introduced of late years.
Cotton .is a kind of down which fills the seed pods of various species of plants, paiticulatly the Gossypi um herbaceum, hirsutum, and arboreunt, from all of which it is extracted in considerable quantity for the purposes of manufacturers. This substance was known to the ancients, and made by them into thread and cloth. Cotton cloth appears to have been ge nerally worn in Egypt and the neighbouring coun tries at a very early period ; and no doubt the plant was cultivated in India and China for similar pur poses before the time at which the history of these nations, as far as we are acquainted with it, com mences. Pliny gives a short description of the gos sypium which grew in Upper Egypt, which is suffi cient to show us that it was the same with our cotton plant. " Superior pars /Egypti in Arabiam vergers gignit fruticem, quern aliqui gossipion vocant, plures nylon, et ideo line inde facts xy/ina. Parvus est, si • milemque barbatte nucis defers frustum, cujus ex interiore bombyce tango netur. Nec ulla cunt eis in candore mollitiave prteferenda." (Plinii, Natur. Hist. Lib. xix. c. 2.) The byssus mentioned in the same chapter was probably likewise a species of cot ton ; though the account of it given by Pliny is not sufficiently precise to enable us to make out the point with certainty.
Since the discovery and colonization of America and 'the West Indies, and our great connection with East India, cotton has become a very common article of clothing in Europe. The manufacture of cotton cloth in consequence has increased prodigiously, and in Great Britain constitutes one of the great branches -of manufacturing industry. As it does not go through the complicated processes of flax and hemp, and is naturally (for the most part at least) of a lighter colour, the art of bleaching it is much more easy and less expensive. The processes are nearly
the same as those for linen ; but it will be requisite to go over them shortly, in order to point out the difference in the proportions of the ingredients em ployed, and some other little circumstances which ought to be generally known.
1. The first, or fermenting process, is the same for cottons as for linens. This must be the case, be cause the weaver's dressing, which it is the object of the process to remove, is the same in both cases.
2. But there is a difference in the second process, which consists in exposing the goods to the action of alkaline leys.
Cotton goods are generally exposed to the action of lime diffused through water, so as to constitute what is called milk of lime. The liquid is heated to the temperature of 200°, and the cloth is kept in it from four to six hours. Two or three alkaline pro cesses will be required after this, and the quantity of potash which ought to be used should amount to of the weight of the goods. When the applica tion is to be made at twice, the first of the opera tions should have iths, and the second iths of the whole potash. If three processes are to be gone through, the first and second should have iths each, and the third .ths of the potash.
When heavy cottons are bleached, either boiling or bucking 'may be employed, as described under the head of linens. When the cotton fabrics are light, or contain dyed colours, boiling is generally preferred, and the proportion of alkali diminished one-third, while a quantity of hard or soft soap, equal to the diminution of the alkali, is added to the ley.
8. The third, or oxymuriatic process, is nearly the same for cottons as for linens. The quantity of oxy muriate of lime used, should amount to hth or hth of the weight of the cotton cloth to be bleached. This quantity is divided among two or three operations, an oxymuriatic process following each alkaline process. When three operations are to be performed, the first must have Aths, the second and the third Atha of the whole oxymuriate of lime. When only two operations are to be performed, the first should con tain two-thirds, and the last one-third of the whole. The duration of each steep should be from six to twelve hours, but not longer. If wincing through the solution be preferred, a stronger liquor may be used, and the operation may be finished in fifteen or twenty minutes.