| Sodic chloride added | 0 gram | 5 grams | 10 grams | |
| "Baric chloride" required | 20.0 c.c. | 20.0 c.c. | 19.7 c.c. | |
| Ammonic chloride added | 0 gram | 5 grams | 10 grams | |
| "Baric chloride" required | 20.0 c.c. | 20.0 c.c. | 19.5 c.c. | |
| Calcic chloride added | 0 gram | 1 gram | 2 grams | 5 grams |
| "Baric chloride" required | 20.0 c.c. | 20.0 c.c. | 19.2 c.c. | 19.0 c.c. |
| Zinc chloride added | 0 gram | 1 gram | 3 grams | 5 grams |
| "Baric chloride" required | 20.0 c.c. | 20.0 c.c. | 20.0 c.c. | 20.0 c.c. |
| Ferrous chloride added | 0 gram | 1 gram | 3 grams | 5 grams |
| "Baric chloride" required | 20.0 c.c. | 19.7 c.c. | 19.5 c.c. | 19.0 c.c. |
| Ferric chloride added | 0 gram | 1 gram | 3 grams | 5 grams |
| "Baric chloride" required | 20.0 c.c. | 20.0 c.c. | 20.0 c.c. | 20.0 c.c. |
| Copper chloride added | 0 gram | 1 gram | 3 grams | 5 grams |
| "Baric chloride" required | 20.0 c.c. | 20.0 c.c. | 20.0 c.c. | 20.0 c.c. |
| Potassic Nitrate added | 0 gram | 1 gram | 5 grams | 10 grams |
| "Baric chloride" required | 20.0 c.c. | 20.0 c.c. | 20.0 c.c. | 19.0 c.c. |
| Potassic Nitrite added | 0 gram | 1 gram | 5 grams | |
| "Baric chloride" required | 20.0 c.c. | 20.0 c.c. | 20.0 c.c. | |
| Sodic phosphate added | 0 gram | 1 gram | ||
| "Baric chloride" required | 20.0 c.c. | 22.5 c.c. | ||
| Sodic arsenate added | 0 gram | 1 gram | ||
| "Baric chloride" required | 20.0 c.c. | 20.5 c.c. |
In the absence of ferric salts, phosphates and arsenates count as sulphur.
In two series of experiments for determining the effect of varying amounts of sulphur in the form of ferrous sulphate, we obtained the following results:—In the first series the assay solution was prepared in the manner we have described for Pyrites; and in the second series, by fusion with nitre.
| Sulphur added | 0.050 gram | 0.100 gram | 0.200 gram | ||
| "Baric chloride" | required | (1) | 5.0 c.c. | 10.0 c.c. | 20.0 c.c. |
| " | " | (2) | 4.7 " | 10.0 " | 20.0 " |
| Sulphur added | 0.500 gram | 1.000 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. Rub up together, and transfer to a small porcelain dish; clean out the mortar with the rest of the nitre, and add to the contents of the dish. Cover with a piece of platinum foil, and heat gently with a Bunsen burner till the nitre melts and the stuff shows signs of deflagrating; remove the heat, and allow the action to go on by itself for a minute or so, then heat over the Bunsen burner for 10 minutes. Cool; transfer the whole to the titrating-dish; boil with 500 c.c. of water; remove the small dish and foil; add sodic acetate and acetic acid, and titrate.
For example, 1 gram required 34.5 c.c. of "barium chloride" (standard = 1.005 gram S), which is equivalent to 34.7 per cent. sulphur. The theoretical percentage is 34.8.
Determination of Sulphur in Chalcocite (Grey Copper Ore).—Proceed as in the last experiment but, since the action with nitre is more moderate, no special precautions need be taken on heating. A platinum dish may be used.