150 A. Fedler — Bleaching action of light on colouring matters. [No. 2, 



The general results shown in the foregoing seven tables may be 

 fairly accurately summarized in the following small table. 



General results of experiments on the bleaching action of Sunlight on 



Colours. 







In 







In Dark- 



Diffused 



In Sun- 





ness. 



Day- 



light. 







light. 





Solution of colours exposed to air. Solution unboiled... 



Un- 

 bleached 



Un- 

 bleached 



All 

 bleached 



„ „ „ „ boiled ... 



>> 



1 >, 



Partial 

 bleach- 

 ing. 



„ in vacuo „ 



)) 



JJ 



Un- 

 bleached 



Colourson cotton-wool in atr,in ordinary hygrometric state 



i) 



„ 



Bleached 



,, ,, in vacuo ... 



>i 



M 



Partial 

 bleach- 

 ing. 



„ on uebestus in air, in ordinary hygrometric state 



>> 



sj 



Bleached 



„ „ in vacno 



» 



if 



Un- 

 bleached 



The following general conclusions appear to follow from the above 

 experiments taken in conjunction with a number of others which can- 

 not be described in detail : — 



1. Organic colours, both in solution in water or on dyed fabrics 

 inorganic or organic, exposed freely to the action of air in the presence 

 of the usual atmospheric conditions of moisture, etc., are practically 

 unacted on in darkness even wheu exposed to these conditions for nearly 

 three years. 



2. Organic colours in the conditions mentioned in 1, are also 

 practically unaffected by diffused daylight opposite a north window, 

 even for the same period of nearly three years. 



3. Oi'ganic colours in the conditions mentioned in 1, when exposed 

 to the direct rays of the sun are all bleached, but with varying rapidity. 



4. In the absence of air (moisture, etc.) strong sunlight, even for 

 a period of three years, has practically no bleaching action on organic 

 colours either in solution in water or used as dyes on inorganic fabrics. 

 In the case of organic fabrics partial bleaching occurs. 



5. It hence follows from 4 that the bleaching is not due to any 

 action of light alone or to any volatility of the colouring matters. 



