THE HAMILTON ASSOCIATION. 53 



of sunlight and the atmosphere. For a long time Holland was the 

 centre of the bleaching industry, and this was the case to so great 

 an extent that goods were sent from all parts of Europe to that 

 country to be bleached. 



The process there employed consisted in thoroughly cleaning 

 the goods and then exposing them to the action of the atmosphere 

 for a longer or shorter period as circumstances required. The time 

 consumed in this process extended over from four to six and even 

 eight months. The inconvenience of this delay was so great as to 

 lead to the establishment of bleaching plots, as they were called, in 

 Scotland and Ireland. The methods adopted by the managers of 

 these plots were similar to those practised in Holland, but the time 

 necessary for transportation from one country to the other was saved. 

 These processes continued as the only ones in use until the discovery 

 of the bleaching properties of chlorine, about the close of the last 

 century. As a result of this discovery the time occupied in bleach- 

 ing was very materially reduced, so that now the process of bleaching 

 scarcely requires as many hours as it formerly did months. 



The discovery of the bleaching properties of chlorine marks a 

 decided advance in the art of bleaching ; but although this is quite 

 true, yet it was soon found that chlorine, while quite suitable for 

 certain classes of materials, was wholly unsuitable for others on 

 which it seemed to act in such a way as to destroy their texture and 

 seriously impair their usefulness. In the bleaching of such materials 

 as are injured by the action of chlorine, sulphur dioxide is now 

 employed. 



It is with these two bleaching agents, chlorine and sulphur 

 dioxide, and the chemical reactions brought about by them, which 

 result in bleaching that I propose to deal in this paper. 



The source from which chlorine is obtained for bleaching 

 purposes is bleaching powder, but as this is an artificial product it 

 may be as well to give the original source of chlorine. 



Chlorine, on account of its chemical activity, is never found 

 free in nature, but in combination with some of the metals in the 

 form of chlorides, of which the most plentiful is common salt, a 

 compound of the metal sodium and this gas. The gas is obtained 

 from the salt by mixing it with finely powdered manganese dioxide, 

 and then adding sulphuric acid to the mixture. In the preparation 

 of bleaching powder the gas thus obtained is brought in contact 



