42 TRANSLATIONS AND SELECTED ARTICLES. 
ON THE COLOUR OF WATER. 
BY W. BEETZ.* 
It is only in recent times that explanations based upon actual ex- 
periments have been given of the colour of water in the sea, in lakes, 
and in rivers; it was previously thought sufficient to conceal the 
entire ignorance of a daily-observed phenomenon by hypothesis. 
Bunsen was the first to state, and establish experimentally, the simple 
proposition that “ chemically pure water is not, as commonly assumed, 
colourless, but naturally possesses a blue colour.’’ He observed this 
coloration on looking at a piece of white porcelain through a column 
of water two yards long. He explained the brown to black coloration 
of many waters, especially of North German inland lakes, as arising 
from an admixture of humus; the green colour of the Swiss lakes, 
and, still more so, the siliceous springs of Iceland, as arising from the 
colour of the yellowish base, and of the siliceous sinter surrounding 
the springs, and which is caused by traces of hydrated oxide of iron. 
Wittstein, by careful chemical investigations, has quite recently shown 
that the green colour also derives its origin from organic admixtures. 
According to him, the less organic substance a water contains, the less 
does its colour differ from blue. With the increase of organic sub- 
stances, the blue gradually passes into green, and from this, as the 
blue is more and more displaced, into brown. Water is softer the 
nearer it is to brown, and harder the nearer it is to blue; this does not 
arise from a greater or less quantity of organic substance, but of 
alkali, on which, again, the proportion of dissolved organic substance 
depends. This alkali dissolves the organic substance in the form of 
humic acid. Ifa water does not contain much humic acid, this is not 
caused by a want of humic acid in the ground, but by the fact that 
this ground did not give to the water an adequate quantity of alkaline 
solvent material. 
From these results we may consider the question settled as to why, 
on chemical principles, some waters are blue, others green, and others 
brown. I may be permitted to make a few remarks on some physical 
phenomena which have been observed on coloured waters. 
Formerly water was almost universally classed among those bodies 
which have a different colour in transmitted, to that which they have in 
* From the Phil. Mag. for September, 1862. 
