The Chemistry of Powder and Explosives - Sciencemadness Dot Org

MERCURY FULMINATE 409
HgSA + NaCN + NaNCO + 2NaOH >
HgSO4 + NajSO, + 2NaNCS + H2O
This reaction is restrained by a large excess of thiosulfate, and
even more effectively by potassium iodide. A moderate excess of
thiosulfate is commonly used, and an amount of potassium iodide
FIGURE 94. Mercuiy Fulminate Crystals for Use in Primer Comi)o,>ition
(30X).
equal to 10 times the weight of the fulminate, and the titrathm
for acidity (methyl orange indicator) is made as rapidly as possible.
After that, the same solution is titrated with iodine (starch
indicator) to determine the amount of unused thiosulfate and
hence, by another method, the amount of actual fulminate in the
sample. Speed is not essential in the second titratiun, for the
iodine value docs not change greatly with time as does the alkalinity.
Blank determinations ought to be made because of the