lUOl’OKT OF COIKMICAL LAliOliATOUY 
Exaniinalion 
of White Nile 
water from 
various points 
Cause of 
clarification 
Ilillet Nuer, which is at about the centre of the marshy district, these two amounted to 
53 parts per million {xee table of analyses on paije 393). Notwithstanding this high proportion 
of alkali (both exist as carbonates or bicarbonates), the tendency of which is to keep the clay 
and other finely divided matter in suspension, the water, at least on all the occasions on 
which observations have so far been made, is more or less clear, with floating particles. 
This effect is obviously due to the very large amount of organic matter, which has a 
flocculating effect on the suspended matter similar to that of calcium and magnesium 
compounds. (Net', below, the note on the clarifying effect of iron in this connection,) It is 
interesting to note that as the river flows north, although the slope is slight and the stream 
therefore sluggish, the water gradually becomes more turbid. This effect is evidently due 
to tile reassertion of the influence of the alkali carbonates ; clay formed by the gradual 
decomposition of the material of the river bed and other finely divided matter are taken up, 
and the river again becomes “ white.” 
-\t the end of .Vugust, 190b, which was the termination of the rainy season, 
^Ir. Goodson, on his return from Gondokoro, collected samples of the White Nile water 
at a number of points, and made observations on the appearance and behaviour of the 
water at the time. His notes were as follows : — 
Gondokoro.—The water at this point contained considerable suspended matter of a 
reddish colour similar to that of the Illue Nile in flood, but much less in 
quantity. When this material had subsided the water remained opalescent 
from the presence of clay. 
Bor. — Practically clear. 
Shauibe. — Whiter was practically clear when taken from the river, but soon turned 
yellow and a small amount of sediment was deposited. 
Lake No. — Colourless and practically clear. A small amount of suspended matter was 
noted. This quickly settled and turned brown. 
Ivodok.—Similar to the water at Lake No, but was more yellowish and contained more 
suspended matter. 
El Dueim. — Only slightly yellowish in colour. Clear, with a very few particles in 
suspension. These turned brown and settled quickly. 
Geteina.—No longer clear. The water was distinctly opalescent from the presence of 
suspended clay, and had the usual appearance which characterises the 
W’hite Nile water near Khartoum. 
It is interesting to note that the clay was taken up when tlie river was moving so 
slowly that no appreciable current could be detected. At this season the Whiite Nile is 
held up by the waters of the Blue Nile to such an extent that the river above Khartoum, 
and up and beyond El Dueim, has, as has already been noted, more the character of a lake 
than of a stream. The effect of the sodium and potassium carbonates in bringing into 
suspension the tine particles of clay, etc., is thus all the more clearly apparent. 
The fact was noted that the water at Shambe was colourless when taken from the 
river, but that it became turbid and deijosited a yellow sediment when exposed to the air. 
This is obviously due to the presence of a soluble salt or salts of iron, the existence of 
which in the ferrous condition was made possible by reason of the presence of the large 
amount of dissolved organic matter and consequent lack of oxygen. On exposure to air 
this iron becomes oxidised and deposited as ferric hydroxide, probably more or less 
combined with organic matter. There aj^pears to be no doubt that the precipitation of 
this iron aids very materially in the clarification of the water which takes place between 
the Sudd region and Geteina. 
