3GG BLEACHING 



however, has proposed the use of acetic acid, or of a sour bran liquor, as substances 

 which are absorbed by the cotton and render it capable of absorbing colour or solu- 

 tions. The matter which prevents the moistening has not been thoroughly examined. 

 It is found to be soluble in alcohol or ether, and some of it in turpentine : it is there- 

 fore called a resinous, waxy, or fatty body. It is dissolved by alkalis, and thrown 

 down by acids in strong solutions. The alcohol solution leaves thin yellowish scales, 

 which may be dissolved in acid, or even in much water. But information concerning 

 it is indistinct. For a long time the process commenced by removing this resin by 

 means of alkali. It is called scouring. 



b. The whole colouring-matter is not soluble in alkalis, but it becomes so after 

 being altered by the action of chlorine, or by insolation or croft-bleaching. It is not 

 even capable of being bleached, or at least but slowly, unless it be previously acted 

 on by alkalis. The amount of colour is much less with cotton than linen. The 

 former is so white naturally, that washing and bleaching might be dispensed 

 with, were it not for the substances which, during its manufacture, come in contact 

 with it. if the gum were removed which prevents the moistening. The alkaline solution 

 from the raw linen, when precipitated by acids, throws down a nearly black resinous 

 mass, and the total loss of weight is very great. 



c. The weaver's dressing is composed chiefly of farinaceous, glutinous, or gelatinous 

 substances, starch, flour, or size. They are usually allowed to become sour before 

 using. They are all dissolved by water or alkaline solutions, including lime. When 

 the dressing gets dry, the hand-weaver occasionally renders his warp-threads more 

 pliant by rubbing some cheap kind of grease upon them. Hence it happens that the 

 cloth which has not been completely freed from this fatty matter will not readily im- 

 bibe water in the different bleaching operations ; and hence, in the subsequent pro- 

 cesses, these greasy spots, under peculiar circumstances somewhat like lithographic 

 stones strongly attract the aluminous and iron mordants, as well as the dyostuffs, 

 and occasion stains which it is almost impossible to discharge. The acids act dif- 

 ferently upon the fatty matters, and thence remarkable anomalies in bleaching take 

 place. When oil is treated with the acetic or muriatic acid, or with aqueous chlorine, 

 it evolves no gas, as it does with the sulphuric and nitric acids ; but it puts these 

 substances into a condition in which they cannot be dissolved by a strong boiling lye 

 of caustic soda. Carbonic acid is said to have a similar action with oil. 



d. Both cotton and linen contain a little fatty matter, which is removed in the same 

 manner as the resinous. Some of it comes from the mode of treating the warp, which 

 is occasionally greased for weaving. This prevents, like resinous matter, the thorough 

 saturation by solutions which are not alkaline, and soap, soda, or potash may bo used 

 to remove it by solution. Lime makes an insoluble soap, and is therefore not suited 

 to the operation. If, however, lime has been used, the insoluble soap may be removed 

 by treating with carbonate of soda, which forms a carbonate of lime, and leaves the 

 fat in combination with the alkali. The carbonate of lime is then removed by an acid. 

 This is, however, an indirect method ; and the mode universally used is to decompose 

 the lime-soap by an acid, and remove the lime, leaving the fat in the cloth ; then to 

 wash out the fat by an alkali, or by soap and alkali mixed, as is the custom almost 

 everywhere. The soap used is in great measure a resinous one, for cheapness, and it 

 is mixed with carbonate of soda. 



e. When the hand-weavers' grease continues in contact for a night with the copper 

 dents of his reed, a kind of cupreous soap is formed, which is sometimes very difficult 

 to remove from the web. Lime-water does not dissolve it ; but dilute sulphuric acid 

 carries off the metallic oxide, and liberates the margaric acid, in a state ready to be 

 acted on by alkalis. 



/. When cloth is boiled with milk of lime, the grease which is uncombined unites 

 with that alkaline earth, and forms a calcareous soap, pretty soluble in a great excess 

 of lime-water, and still more so in caustic soda. But all fats and oils, as well as the 

 soaps of copper and lime, cease to be soluble in alkaline lyes when they have remained 

 a considerable time upon the goods, and have been in contact with acetic, carbonic, 

 or muriatic acids, or chlorine. These results have been verified by experiment. 



g. Cotton goods are sometimes much soiled, from being sewed or tamboured with 

 dirty hands ; but they may easily bo cleansed from this filth by hot water. 



A. Any ferruginous or earthy matters which get attached to the goods in the course 

 of bleaching are readily removable, if not allowed thoroughly to penetrate the cloth ; 

 but the fine ferruginous clay found in suspension in water is very difficult to wash off, 

 and it probably cannot, by any means, be removed from printed goods without spoiling 

 the colours. 



t. In all these operations it is needful to consider the most important substance of 

 all the fibre. Each of the operations may weaken or destroy it, if managed unwisely. 

 Caustic lime may be allowed to act for a long time on cloth without any injury, but 



