180 A. B. MACALLUM. 
hydrogen sulphide is more active than the diammonium salt, 
and that none of the polysulphides of ammonium have any 
action whatever on iron in its “ masked” form. These experi- 
ments have been controlled by others made with these reagents 
upon solutions of potassium ferrocyanide.!| Ammonium sul- 
phide, when mixed with a solution of the latter salt and the mix- 
ture kept at a temperature of 30—50°C. for one or more days, 
will liberate the iron from its combination and precipitate it as 
sulphide, the amount so liberated depending on the strengths 
of the solutions forming the mixture, on the temperature and 
on the time during which the reaction is allowed to goon. A 
lower temperature will suffice when the time is prolonged. 
By paying due attention to all the conditions, it is possible to 
liberate, as sulphide, all the iron of such solutions. In this 
ammonium hydrogen sulphide is more active than diammonium 
sulphide, the amount of the sulphide formed being a measure 
of the activity of either reagent.” These experiments have, in 
all cases, given results which correspond with those obtained 
with the two sulphides upon the chromatin of isolated cells, 
but it was not possible in the latter case to estimate the effects 
as definitely. I found that of two slide preparations of isolated 
cells, one made with ammonium hydrogen sulphide, the other 
with diammonium sulphide, the former as a rule gave the 
1 T have not found any reference to the action of ammonium sulphide on 
solutions of ferrocyanides in the literature of chemistry, although, on the pre- 
sumption that some such reference exists, I made diligent search for it. 
2 The results of one experiment upon this point may be mentioned. The 
glass-stoppered cylinder a contained 10 c.c. of a 10 per cent. solution of 
potassic ferrocyanide and 10 ¢.c. of ammonium hydrogen sulphide made from 
an ammonia solution of 0°96 sp. gr., while to a similar cylinder 4, with like 
quantities of the same solutions, 10 ¢.c. of dilute ammonia were added. At 
the end of twenty-four hours’ stay in a warm oven with a temperature of 
40° C., the precipitates were filtered off with iron-free filters, washed with 
water containing hydrogen sulphide in solution, dissolved in dilute sulphuric 
acid solutions, and, after care had been taken to reduce all the iron to the 
ferrous condition, the amount of the metal in each case was estimated by 
titration with a standardised permanganate solution. Results: the precipi- 
tate in a contained 0:0113 grm. iron, while the iron of the precipitate in J 
amounted to 0:0025 grm. 
