BLEACHING 391 



7. Boiled with soda -ash for ton hours; 110 Ibs. used. 



8. Washed and spread out on the green, or crofted. 



9. Boiled again in soda as before. 



10. Crofted for three days. 



11. They are then examined: the white ones are taken out; those that are not 

 finished are boiled and crofted again. 



12. Next, they are scalded in -water containing 80 Ibs. of soda-ash, and washed. 



13. The chloride of lime is then used at Twaddle, or 1002-5 specific gravity. 



14. Washed and scalded. 



15. Washed and treated with chloride of lime. 



16. Soured, for four hours, with sulphuric acid, at 2 Twaddle, or 1010' specific 

 gravity. 



17. Washed. 



If cloths lighter than sheetings are used, the washing liquids arc used weaker. The 

 great point is to observe them carefully during the process, in order to see what 

 treatment will suit them best. 



It will be seen that the process of bleaching linen is still very tedious ; and although 

 it may be managed in a fortnight, it is seldom that this occurs regularly for a great 

 length of time. The action of the light introduces at once an uncertain element, 

 ;is this varies so much in our climate. If, again, linen bo long exposed to the 

 air in a moist condition, it is apt to become injured in strength. To shorten the pro- 

 cess, therefore, is important ; and if no injurious agents are introduced, a shortening 

 promises also to give increased strength to the fibre. It has not been found possible 

 to introduce chlorine into linen-bleaching at an early stage, as in the case of cotton ; 

 and the processes for purifying it without any chlorine, render it so white that un- 

 skilled persons would call it as white as snow. The chlorine is introduced nearly at 

 the end of the operation, after a series of boilings with alkalis, sourings, and ex- 

 posures on the grass. If introduced at an earlier stage, the colour of the raw cloth 

 becomes fixed, and cannot be removed. The technical term for this condition is ' set.' 

 Mr. F. M. Jennings, of Cork, has patented a method which promises to obviate 

 the difficulty. The peculiarity consists in using the alkali and the chloride of alkali 

 at the same moment, thus giving the alkali opportunity to seize on the colouring- 

 matter as soon as the chloride has acted, and thereby preventing the formation of an 

 insoluble compound. He prefers the chlorides of potash or soda. His plan is as 

 follows : 



1. He soaks the linen in water for about twelve hours, or boils it in lime or alkali, 

 or alkali with lime, and then soaks it in acid, as he uses soaps of resin in other mix- 

 tures the alkalis being from 3 to 5 Twaddle, 1015--1025' specific gravity. 



2. Boils in a similar alkaline solution. 



3. Washes. 



4. Puts it into a solution of soda, of 5 Twaddle, 1025 1 specific gravity, adding 

 chloride of soda until it rises up to from 6-7 Twaddle. It is allowed to remain in 

 this solution for some hours, and it is better if subjected to heating or squeezing be- 

 tween rollers, as in the washing-machine. 



5. He then soaks, sours, and washes. 



6. Ho then puts it a second time into the solution of alkali and chloride. 



7. Then washes, and boils again with soda. Those operations, 6 and 7, may bo 

 repeated until the cloth becomes almost white. 



The amount of exposure on the grass by this process is said to be not more than 

 from one-half to one-fourth that required by the usual method, or it may be managed 

 so as entirely to supersede crofting. 



Chevalier Claussen has opened up the filaments of flax by the evolution of gas from 

 a carbonate in which the plant is steeped, and at the same time bleached by chloride 

 of magnesia, but this has not been successful. 



BLEACHING OF SILK. 



Silk in its raw state, as spun by the worm, is either white or yellow of various 

 shades, and is covered with a varnish which gives it stiffness and a degree of elasticity. 

 For the greater number of purposes to which silk is applied, it must bo deprived 

 of this native covering, which was long considered to be a sort of gum. The 

 operation by which this colouring-matter is removed is called scouring, cleansing, 

 or boiling. A great many different processes have been proposed for freeing the silk 

 fibres from all foreign impurities, and for giving it the utmost whiteness, lustre, and 

 pliancy ; but none of the new plans has superseded, with any advantage, the one 

 practised of old, which consists essentially in steeping the silk in a warm solution 

 of soap ; a circumstance placed beyond all doubt by the interesting experiments of 



