ON THE ABSORPTION OF LIGHT BY TURBID SOLUTIONS, 187 



XXII. Colorimetry. — Part V. On the Absorption of Light 

 by Turbid Solutions. By James Bottomley^ D.Sc. 



Bead before the Physical and Mathematical Section, April 27th, 1880. 



Media containing colouring-matter may be divided into 

 two classes^ transparent and turbid. It might be consi- 

 dered that in their behaviour with regard to light they 

 were wholly dissimilar. But the question arises, Is not the 

 difference between transparency and turbidity one of degree? 

 Experience in the laboratory brings under our notice cases 

 where matter is so finely divided as not to be separable 

 from fluids by filtration, and showing but slight tendency 

 to settle as a precipitate ; and in some cases we have liquids- 

 which are apparently transparent, and yet are considered 

 to hold solid matter in suspension. May not such examples 

 be intermediate between solutions and cases where ex- 

 tremely fine particles are uniformly diffused through some 

 transparent medium ? If, then, we consider the passage 

 from transparency to turbidity a continuous one, and if 

 for a transparent fluid we have established some law of ab- 

 sorption of light, may not the same law be applicable to a 

 turbid solution ? The subject seemed to me interesting 

 both as a scientific inquiry and on account of its application 

 to quantitative analysis. 



Suppose we have diffused through a liquid some finely 

 divided solid matter ; the action of such a turbid solution 

 on light will be twofold : it disperses light and it absorbs 

 light. By reason of the first action we are made aware of 

 the colour of the turbidity ; by reason of the second any 



