Potassium Permanganate and Sulphuric Acid. 



107 



the available oxygen of the permanganate. The remaining 

 39 per cent must have gone with the precipitated oxide or 

 have remained in solution as a higher sulphate. That but 

 little of the higher sulphate did remain, however, is shown by 

 comparison of A with B, in which after thirty-five days the 

 liquid was entirely bleached. The gas finally set free in B 

 amounted to 64*4 per cent of the available oxygen of the 

 permanganate, and the remainder, 35*6 per cent, would be 

 enough to throw down about 90 per cent of the entire amount 

 of manganese in the permanganate in the degree of oxidation 

 of Mn0 2 . It is noteworthy that the stronger acid, 50 per 

 cent [1:1], still held some of the higher oxide in solution 

 until the end, and that the acid of 25 per cent [1 : 1] allowed 

 the decomposition to pass to completion in thirty-five days, 

 while the smaller amounts of acid, 1^*5 per cent [1 : 1] and 

 6 - 25 per cent [1 : 1], brought about in forty-four days decom- 

 position amounting respectively to 42 per cent and 17 '5 per 

 cent respectively. 



Table IV. 



Percentage Time elapsed. 



f , C 



H 2 SOj[l:l] 1 day, 2 days, 3 days, 4 days, 



Percentage 



> of K 2 Mn 2 8 



5 days, decomposed. 



10 



20 

 30 



40 



50 

 60 



'70 



Color 



Color 



Color 



Color 



Color 



unchanged, 

 ii 



unchanged, 

 ti a 



unchanged, 

 ii it 



unchanged. 



Slight 

 sediment. 



Color 



unchanged. 



Slight 



sediment. 



unchanged. 



Slight 



sediment. 



Slight 



scum . 



Color 



unchanged. 



Slight 



sediment. 



u i: 



u ii 



a ii 



Reddish 

 tinge. 

 Slight 



sediment. 



Reddish 



tinge. 



ii ii 



11 « 



Tinged with 



Reddish 



Reddish 







reddish 



. brown. 



brown. 







brown. 







it it 



11 11 



Reddish 



Reddish 



Red 







brown. 



brown. 



brown. 



Color 



Color 



Reddish 



Sherry 



Reddish 



redder. 



redder. 



brown. 



brown. 



olive. 



a a 



ii i. 



Sherry 



Reddish 



Reddish 







brown. 



olive. 



olive. 



103-6 



107-4 

 106 9 



139-2 



157-4 

 158-9 

 161-1 



It seemed to be desirable in this connection to make the 

 experiments detailed in Table IY, in which note is made of 

 changes in color and formation of precipitates in 100 cm 3 por- 

 tions of liquid containing 10 cm 3 of decinormal permanganate 

 and varying proportions of acid during five days' standing, 



