000 gram
"Baric chloride" required (1) 50.0 c.c. 100.0 c.c.
" " (2) 50.0 " 100.0 "
More than 5 grams of nitre must not be used in an assay; and, since the
requisite amount of nitre considerably exceeds that sufficient to
oxidise the sulphur, not more than 0.5 gram of unoxidised sulphur should
be present in the portion of the sample weighed up for determination.
When the amount of sulphur present is not known within reasonable
limits, the test portions may be tried with a drop of baric chloride
solution instead of sulphuric acid, so that the diminishing quantity of
precipitate may give warning of an approach to the finishing point.
~Determination of Sulphur in Blende.~--Weigh up 1 gram of dried and
powdered blende, and mix and fuse with 5 grams of nitre in the manner
described. Place the dish and its contents in the titrating-dish,
extract with water, add 10 grams of sodium acetate and 10 c.c. of acetic
acid, remove and wash the platinum-dish, and dilute to 500 c.c.; boil
and titrate. In the example, duplicate determinations required (a)
32.0 c.c., (b) 32.25 c.c., giving an average of 32.1 per cent. of
sulphur.
~Determination of Sulphur in Chalcopyrite~ (Yellow Copper Ore).--Take 1
gram of the finely-powdered sample, and 5 grams of nitre. Sprinkle a
little of the nitre in a small Wedgwood mortar, place the ore on it, and
cover with 2 or 3 grams more of the nitre.
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