192 
With transmitted light they were all equally clear and of the 
same colour. 
With powerful incident light Ila was somewhat turbid but, on 
shaking, without a silky lustre; the others were always turbid ina 
steadily increasing degree and always exhibited an increasing silky 
lustre. 
Placed in a 5 mm. wide cuvette between crossed nicols through 
which passed Na-light la gave on stirring with a glass rod a very 
faint luminosity. With 115 the luminosity was very bright and 
regular and quickly disappeared when stirring ceased. With IIc a 
strong flashing took place, not regular however; dark and luminous 
schliers passed through the field, which again disappeared slowly ; 
Hd and Ile exhibited this phenomeon still much stronger. Even 
without stirring the entire field was filled with dark and luminous 
schliers, which on stirring changed places. It made the impression 
as if a part was gelatinised. Also macroscopically the schliers in 
the cuvette were very plainly visible and when emptying the cuvette 
gelatinous, little lumps were present which, however, on dilution 
with water disappeared and dissolved evenly. The viscosity of the 
heated sols, particularly of Ile, was plainly greater than that of 
the unheated sol. *) 
On examining under the ultramicroscope *) with cardioid-condenser 
[Ia exhibited many small strongly luminous ultramicrones with little 
or no difference in longitudinal or latitudinal dimension. 
IIA exhibited, beside these more circular and very luminous par- 
ticles, very slender, faintly luminous long needles in the background. 
With IIe these slender bluish-luminous needles are more predo- 
minant, the whole field is filled with them and the bright luminous 
round particles have mostly disappeared. 
[Id also yielded many of these slender needles both very small 
and larger ones. Whereas, however, in the previous sols the particles 
1) Two days after these experiments, the viscosity of these sols was determined 
with an Osrwarp viscosimeter. The results were (temp. 20°). 
Flow Relative viscosity 
in seconds as compared with water 
water 93,0 1,00 
lla 167,0 1,80 
IIb 194,2 2,09 
[Ic 209,0 2,25 
Id 248 2,64 
[le 663 1,18. 
2) Zeiss apochromatic V, compensation ocular 18. 
