100 
RuS,O,, +40 = Ru(SO,), + 2S0,, 
which was completely checked and confirmed by the deter- 
mination of the oxygen liberated from the permanganate used and 
absorbed by the substance, as well as by the quantitative measurement 
of the amount of sulphuric acid formed. For this latter quantity is 
equal to the total amount of acid found, minus the acid added for 
the volumetric analysis, plus the quantity of acid used during the 
titration with KMnO,. 
Analysis: A quantity of the colloidal solution, containing 2,30 
mGr. of ruthenium (= 0,0225 milli-mol. Rw) was titrated with 10 
1 
ecm. of a 35 normal solution of sulphuric acid and 4,9 eem. KMn0, 
of 0,09 normal, — if a normal solution be calculated as one con- 
taining 0,4 mol p. Liter, equivalent to 0,09 mGr. atom  p. cem. 
Therefore, totally 0,0882 mGr. O, corresponding with 40 to 1 Ru 
were used. As there are used at the same time 2,65 cem. H,SO, 
of the strength mentioned above in this reaction, 7,385 ccm. sulphuric 
acid remain. As 38 eem. of +; normal NaQOH-solution were 
necessary in the subsequent titration, and for 7,85 ecm. H,SO, 
only 29,4 of this MaOH-solution were necessary, it follows tbat 
0,043 milli-mol. H,SO, are formed in the reaction by oxydation of 
the sulphur. For every atom fw there are thus formed 2 molecules 
A,SO,, which data, with respect to the quantity of O absorbed in 
the process, demonstrate clearly the correctness of the equation just 
mentioned. . 
§ 5. Thus, while the original greenish black sulphide appeared 
to be RuwS,, this is transformed by vigorous absorption of atmospheric 
oxygen into the reddish violet compound RuwS,O,,, with simultaneous 
splitting-off of free sulphur, according to the equation: 
RuS, + 50, = RuS,O,, + 28, 
while the compound formed is afterwards further oxydized by the 
potassium permanganate according to the equution: 
RuS,O,, + 40 = Ru(SO,), + 2H,Q,. 
The red colloid is, therefore, by no means to be considered as 
the final oxydation-product of the greenish black sulphide, but it 
represents an intermediate stage on the way leading finally to 
ruthenium sulphate. This fact too could be contirmed by special reactions : 
a. Strong mitric acid oxydizes the red coloured solution at low 
temperatures slowly, but on heating more rapidly, to a solution 
which appears to contain free sulphuric acid. 
b. A solution of potassium permanganate makes the colour of the 
