M. TECHNOLOGY. 535 



analogous results. As to the influence of the different condi- 

 tions in which the solution of the mordant is applied, Mr. 

 Havrez found, first, that lime dissolved in the water acts like 

 a diminution of the mordant ; second, that the presence of 

 free acid in small quantity does not prevent dissociation, but 

 reduces the amount of alumina absorbed by the wool ; third, 

 that most diluted solutions of alum, at the highest tempera- 

 ture, and by their long-continued action, produce the most 

 extended dissociation and fix the most alumina. Besides, the 

 ratio of the quantity of wool operated on to that of the alum 

 applied is of greater influence than the proportion of the 

 solvent to the alum. 



In summing up, Mr. Havrez maintains that the elements 

 of the mordants, separated by dissociation, are gradually and 

 very unequally absorbed by the wool, so that the whole 

 process appears as a kind of dialysis, in which the wool acts 

 the part of the porous body. Bull. Acad. Royale des Sciences, 

 JBruxelles^ 3farch y 1872. 



NEW MODE OP FEINTING GOODS. 



Mr. Vial presented to the Academy of Sciences, in Paris, a 

 new method of printing upon fabrics by means of metallic 

 precipitation. An illustration of the process is seen if we 

 take a piece of linen, cotton, or silk fabric, and soak it for a 

 time in a solution of nitrate of silver. After exposing this 

 to the air for a short time for the purpose of partially drying, 

 if we place above it a coin, or a casting of zinc, lead, or cop- 

 per, the nitrate will be decomposed in places where contact 

 has been effected and the silver immediately precipitated in 

 the form of a black powder, representing the image upon the 

 coin in its minutest details, and in a faithful, distinct, and in- 

 delible manner. Every time the coin is placed upon the 

 moist cloth the impression will be repeated instantaneously 

 and perfectly, this not being the result of the application of 

 color, but a chemical phenomenon exhibited by the simple 

 contact of the salt and the metal, whatever be the delicacy 

 or extent of the point of contact, and the deposition of the 

 silver is made with such intensity as to strike almost entire- 

 ly through the material. 



Simple washing with water will remove from the cloth the 

 undecomposed salt. The tint of the impression may be va- 



