98 
extraction of the product by carbon disulphide at low temperatures. 
The substance was, therefore, rapidly put into a small ERLENMEYER- 
tlask, carbon bisulphide was poured upon it, the air driven out by 
carbon dioxide, and the flask shaken for some time at room-temperature. 
This treatment was repeated several times, till no sulphur was any more 
extracted ; the carbon bisulphide was then washed out by a mixture of 
dry alcohol and ether, the product finally washed with absolute ether 
and carefully dried in an atmosphere of carbon dioxide. For the 
purpose of analysis a weighed quantity was put into a Rosr- 
crucible, which in its turn was hung inside a nickel crucible, and 
carefully roasted with access of the air; afterwards it was ignited 
in a current of dry hydrogen. All the determinations were made by 
means of a micro-balance. 
Analysis: 12,33 m.Gr. of the greenish black sulphide gave 4,26 
m.Gr. Ru; calculated for RuS,: 34,69°/, Ru; found: 34,55 °/, Ru. 
Because in the oxydation of this sulphide, as will be demonstrated 
below, there is formed a substance containing four atoms of sulphur, 
while simultaneously sulphur is set free, this high content of sulphur 
is perfectly in agreement with the whole chemical behaviour of the 
greenish black sulphide’), which has the character of a ruthenium 
persulphide. 
§ 4. We must now first review the properties of the red-violet 
solution, which is formed by oxydation of the green solution described 
above. Its refractive index appeared to be practically identical with that 
of pure water; moreover, besides the TyNparr-effeet and the Brownian 
movement, it manifests in a particularly beautiful way the phenomenon 
of electric cataphoresis: the dispersed particles possess, in contra- 
distinction to those of the green colloidal solution, a positive charge. 
Although the solution is very stable, and may even be concentrated 
on the water-bath without coagulation, it can be flocculated by 
the addition of electrolytes, — be it only slowly. The pure solution 
was mixed with a small quantity of solutions of NH,C/, CaCl, 
Fe, Cl,, KySO, and Na,HPO,. Already after a day some precipitate 
was formed from each of these liquids, and the intensity of their 
colour diminished. If more of the electrolytes be added, the precipitate 
formed first again disappears, but after twenty-four hours a certain — 
quantity is again deposited. After a couple of days the colour of the 
liquid has completely disappeared, and all of the dispersoid has been 
flocculated. Most rapidly this takes place, when phosphate is added, 
') It may be remarked here, moreover, that on heating this sulphide at the 
open air at 120° C., also SO» is formed; the sulphur seems to be partially more 
loosely bound than the remaining part of it. 
