150 A. Pedler —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 Dark¬ 
ness. 
In 
Diffused 
Day¬ 
light. 
In Sun¬ 
light. 
Solution of colours exposed to air. Solution unboiled... 
Un¬ 
bleached 
Un¬ 
bleached 
All 
bleached 
,, ,, ,, ,, boiled ... 
>> 
1 „ 
Partial 
bleach¬ 
ing. 
,, in vacu3 „ 
i> 
Un¬ 
bleached 
Colours on cotton-wool m air, in ordinary hygrometric state 
it 
Bleached 
yy yy III YfilCHO ••• • •• ••• 
J> 
» 
Partial 
bleach¬ 
ing. 
„ on asbestus in air, in ordinary hygrometric state 
a 
Bleached 
yy yy 111 VaCUO • • •• • ••• 
>9 
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 when 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. Organic 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. 
