M. TECHNOLOGY. 545 



Fahr., and one part of soluble glass ; plunge the wool into 

 the mixture, stirring it about for a few minutes by hand; 

 then rinse it in cold or tepid water, and it will be found com- 

 pletely white and without smell. The wool after this opera- 

 tion remains perfectly soft, and loses none of its qualities, 

 even when left for several days in the solution of the silicate, 

 and then washed in hot water. 



Sheep may also be washed with the same preparation, care 

 bein; taken to cover the eves of the animals with a bandage, 

 as also to perform the washing with the solution instantane- 

 ously, and to remove the surplus with tepid water. In the 

 case of combed wool this should be first steeped in the above 

 solution, and afterward in another, having eighty parts of 

 water, at about 100 Fahr., and one part of soluble glass. 

 4 D.October 19, 1872, 242. 



CONVERSION OF INDIGO-BLUE INTO INDIGO-WIIITE. 



It is well known that if, in any manner, one equivalent of 

 hydrogen be added to indigo-blue or commercial indigo, the 

 former becomes changed to a substance known as indisro- 

 white; and that if yarns be impregnated with this, without 

 being previously mordanted and exposed to the atmospheric 

 air, the indigo-white loses one equivalent of hydrogen by the 

 absorption of one equivalent of oxygen, and is again trans- 

 formed into indigo-blue, the fabric or yarn becoming a genu- 

 ine blue color. This transformation of indi^o-blue into in- 

 digo-white, according to Professor Bottger, can be made very 

 readily by boiling the finely powdered indigo with a solution 

 of stannous hydrate of tin in caustic soda. G (7, xxxi., August 

 3,1871,308. ' 



BORAX FOR DRYING OIL AND TARNISH. 



The use of borax as an agent for causing the rapid drying 

 of varnish and of oil colors has become extensive ; and one 

 method of its application consists in taking one hundred parts 

 of water, twelve parts of shellac, and four parts of borax, and 

 melting them at a gentle heat in a copper vessel, with con- 

 tinued stirring. The vessel is then to be covered, and the 

 liquid allowed to cool ; after which it is to" be kept in well- 

 closed bottles. This furnishes an excellent varnish, jnvinor a 

 beautiful and durable lustre, and is perfectly secure against 



