428 Miscellaneous Intelligence, 



then the cloth replaced for half an hour without a<ritation : the cloth 

 is then to be placed on the wheel, the bath heated, the cloth passed 

 throu^li, and then taken away and passed through cold water. 



iii. Milling. This is to be done at common temperatures, with 

 a solution of 1 part of soap in 20 parts of water for 20 parts of 

 cloth by weight. 



iv. Brightening. The brightening of deep blues is done by 

 plunging the cloth for twenty-five or thirty minutes in water con- 

 taining one three-hundredth of its volume of ammonia. As this gives 

 too grey a hue to clear blues, an acid water consisting of 5 parts of 

 cream of tartar dissolved in 10 parts of water and added to 1000 

 parts of water, is prepared for them. This is heated by steam, and 

 the cloth passed through it for twelve or fifteen minutes, after 

 which it is washed in running water. 



A kilogramme (about '2\ lbs.) of cloth dyed blue in this man- 

 ner costs IJ francs, whilst dyed with indigo it would cost more than 

 double. Prussian blue thus applied on wool resists the action of 

 cold water, of air, the sun, friction ; has the characters of a good 

 solid colour, and more lustre than indigo. 



The commissioners proved by their own experiments that the 

 pertartro-sulphate of iron is a very proper agent for the transference 

 of oxide of iron to wool, and may be in this respect employed with 

 great advantage in many dyeing operations. 



M. Raymond also remarks a peculiar change in the mechanical 

 properties of wool occasioned by chlorine. When passed through 

 a bath of that substance in solution, the wool becomes silky and 

 loses its property of felting ; a change which, though it might be 

 advantageous sometimes, would occasionally be very inconvenient 

 and injurious. — Revue Ency. xxxix. 779. 



§ II. Chemical Science. 



1. Electro-chemical Theory of Combination. — One part of this 

 theory, according to certain persons, supposes that elements capable 

 of combining are in opposite states of electricity ; that when they 

 combine, the electrical attractions draw them together, and that in the 

 act of combination these electricities mutually neutralize each other. 

 The discharge of the electricity has been considered as the source 

 of the heat and sometimes light evolved, as in combustion. This 

 view involves the difficulty, that after the electricities are neutralized 

 the attraction supposed to depend upon them still continues. 

 Upon this, M. Fechner remarks, that the difficulty no longer exists 

 if it be supposed that there is a separation of electricity equivalent 

 to a discharge before the particles come into actual contact. On 

 this view chemical light and heat are not the consequence of the 

 union of different electricities, but of their separation. When two 

 combining particles are found within the distance of molecular 

 attraction they will always remain in opposite states of electricity, 



