84 Mr. Colquhoun on the Life and Writings [Feb. 



gent bleachers who did not follow their business as a mere 

 routine. M. Caillau at St. Quentin, Descroisilles at Rouen, 

 Bonjourat Valenciennes, and Welter at Lille, all men of consi- 

 derable eminence, who could join science with art, introduced 

 the benefits of the new system into various parts of the empire. 



But there are many other processes in the arts besides that of 

 the simple bleaching of dingy cloth, in which the removal of 

 certain colouring matters is advantageous, and which were of 

 course susceptible of great improvement from the application of 

 Berthollet's discovery. One of the earliest and most important 

 of these was first suggested by our chemist himself: it relates 

 to that process in calico printing which is technically known by 

 the appellation of brightening. When a piece of calico is dyed 

 with madder, the portions meant to be preserved white are 

 found to have contracted a dull red coloured stain ; because, 

 although colouring matters in general cannot form a permanent 

 union with cloth except through the intervention of some mor- 

 dant, they have often an immediate affinity for the cloth of such 

 strength, as requires considerable labour for their complete 

 removal. The old process for removing such discoloration was 

 to boil the cloth in a mixture of bran and water, and then to 

 expose it to the action of air and moisture for a period of from 

 one to six, or even eight weeks together. This was generally a 

 successful, but always a most tedious, operose and costly 

 system. But the delay, the labour, and the expense, were 

 very greatly reduced by M. BerthoUet discovering that 

 a very dilute solution of chlorine destroys colouring matters 

 which are attached to the cloth only by their immediate 

 affinity, while it produces no material alteration on such as are 

 held in combination with it through the agency of a mordant. 

 The new process of brightening by chlorine was of course imme* 

 diately and universally adopted in all the calico print fields in 

 France, and has now become part of the ordinary routine of that 

 business. 



But we are still far from having enumerated even the principal 

 uses to which the bleaching property of chlorine was found 

 applicable. By means of it, BerthoUet was enabled to instruct 

 his countrymen in an expeditious and, at the same time, a most 

 accurate method of ascertaining the relative permanency of 

 colouring matters when in combination with cloth. By means 

 of it, Descroisilles brightened turkey red, by destroying the 

 brown colouring matter which contaminates and conceals the 

 beauty of that dye : by means of it, M. le Baron de Born gave a 

 beautiful white to the yellow colour of animal wax, while Ber- 

 thoUet destroyed the green colour of vegetable wax, and gave it 

 the closest resemblance to the bleached wax of de Born : by 

 means of it, M. Chaptal succeeded in removing the stains from 

 old books and prints : by means of it, Loysel bleached coloured 



