Joty—The Inner Mechanism of Sedimentation. ool 
9. Solutions of bodies which are not ionised, such as sugar, 
produce little or no effect. 
10. In acidified K,SO, solution settlement is much faster than 
in alkaline K,SO,, and in alkaline MgCl, or BaCl, settlement is 
faster than in acid MgCl, or BaCl,. It would appear from this that 
a change of sign of the suspended particles is brought about in 
these cases. ‘The acidifying of the solution probably renders 
the particles electro-positive; addition of alkali renders them 
electro-negative. In the first case they are acted on by the 
radicle of the salt (in the experiment SO,”); in the second by the 
_metal (in the experiments Mg” or Ba’’). In each case, therefore, 
the experiment is in accord with Hardy’s results on colloids. 
11. Picton and Linder found that the coagulative effects of salts 
of the same group as regards valency were additive, while with 
successive additions of quantities of salts of different valencies 
they were not additive. I find that among equi-coagulative quan- 
tities, the addition of MgCl, to BaCl, produces a greater effect than 
the addition of MgCl, to NaCl. The “inhibitory” effect noticed 
by Linder and Picton, p. 67 (/oc. cit.), would therefore appear to 
be present in some degree. 
12. In sea-water there are in approximate gram-molecules 
and gram-equivalents per kilo. the following principal salts :— 
Gram-molecules. Gram-equivalents. 
NaCl, 0-472 0-472 
MeCl,, 0-040 0-080 
MgS0O,, 0-014 0028 
CaSO,, 0-009 0-018 
K.S0,, 0-005 0-010 
It will be found on comparing these figures that, on the square 
and cube law, the MgCl, is present in distinctly greater coagula- 
tive strength than the NaCl; that the MgSO, is only a little greater 
in strength, taking its inferior ionisation into account; and, on the 
assumption ofa coefficient of ionisation for CaSO, not much inferior 
to that of the NaCl present, it also is of superior coagulative 
' strength. 
We find in comparative experiments on separate solutions of 
salts made up to the above strengths that MgCl, and CaSQ, are 
the most active in precipitating suspension; next follows MgSO,, 
