186 
DR. GLADSTONE ON CIRCUMSTANCES MODIFYING 
the red salt ; it appears also that the deepest colour is obtained on mixing either ferric 
nitrate with sulphocyanide of potassium, or ferric sulphocyanide with nitrate of pot- 
ash ; whilst the mixtures containing compounds of acetic, sulphuric, and hydrochloric 
acids are intermediate in colour in regular order. Mercury also seems to exert the 
most powerful affinity for sulphocyanogen in whatever way they are brought toge- 
ther. This suggests the conclusion that the amount of sulphocyanide of iron in a 
mixture of salts does not depend on the manner in which the different substances 
were at first combined. The experiment above described was incapable of affording 
a quantitative demonstration of this, as a perfectly pure and definite sulphocyanide of 
iron was not obtained ; but the following arrangement was made to put it to a rigid 
test. Two solutions were made; the first by mixing together 50 grain measures of 
ferric nitrate, and 12‘5 gr. meas. of sulphate of potash; the second by mixing50gr. meas. 
of ferric sulphate, and 12'5 gr. meas. of nitrate of potash; so that each contained one 
equiv. of ferric oxide, three equivs. of potash, three equivs. of nitric acid, and three 
equivs. of sulphuric acid. To each was added 6*25 gr. meas., that is. To equiv. of sulpho- 
cyanide of potassium. The colours resulting in the two cases were so nearly identical, 
that the first diluted to 1770 gr, meas. just equalled the second diluted to 1820 gr. 
meas. Another 6‘25 gr. meas. of sulphocyanide of potassium were added to each. 
The two solutions appeared now identical in colour; they certainly did not differ by 
1 degree in 80. The amount of sulphocyanide of potassium in each was then doubled: 
the resulting colours could not be distinguished from each other. It appears, there- 
fore, that it makes no difference whether there be mixed in solution 
Fe, O3, SNOs-f 3(KO, S03)-|-3KS, Cy or Fe^ O3, 3S03+3(K0, NO*) -h3KS, Cy. 
The influence of the mass of one of the substances that 'produce the coloured salt . — 
The influence of mass has yet to be considered quantitatively. For this purpose two 
mixtures were prepared, each containing 25 gr. meas. of the ferric nitrate, and 6*25 gr. 
meas. of the sulphocyanide of potassium solution. They were both diluted so as to 
occupy 880 gr. meas. The one was kept as a standard of comparison ; with the other 
additional portions of sulphocyanide of potassium were mixed ; and as that increased 
the colour, it was diluted till brought to an equality with the standard solution. 
Original solution. 
Additional sulpho- 
cyanide of potassium. 
Dilution 
required*. 
Original solution. 
Additional sulpho- 
cyanide of potassium. 
Dilution 
required*. 
880 gr. m. 
6*25 gr. m. 
390 gr. m. 
880 gr. m. 
125 gr, m. 
2680 gr. m. 
880 gr. m. 
13'75 gr. m. 
680 gr. ni. 
880 gr. m. 
200 gr. m. 
3310 gr. m. 
880 gr. in. 
20 gr. m. 
880 gr. m. 
880 gr. m. 
275 gr. m. 
3690 gr. m. 
880 gr. m. 
27‘5 gr. m. 
1070 gr. m. 
880 gr. m. 
387*5 gr. m. 
4200 gr. m. 
880 gr. ni. 
33*75 gr. m. 
1250 gr. m. 
880 gr. in. 
500 gr. m. 
4510 gr. m. 
880 gr. m. 
32*5 gr, m. 
1780 gr. in. 
880 gr. m. 
612*5 gr. m. 
4720 gr. m. 
880 gr. rn. 
90 gr. m. 
2300 gr. m. 
880 gr. ni. 
775 gr.m. 
4990 gr. m. 
Beyond this the experiment could not be carried, although evidently no termina- 
tion of the action of additional sulphocyanide had been arrived at. 
* This includes the water in which the sulphocyanide of potassium was dissolved. 
