Neither are these Sulphur colors often used on silk, although methods have been devised for employing them in special cases. All the animal fibres, however, and silk especially, are very easily “tendered,” and indeed destroyed, by heating in an alkaline solution. And so it is very easy to spoil a skein or piece of silk by dyeing it, in the usual manner, with these dyes, dissolved as they must be in the strongly alkaline sodium sulphide. The presence in the bath of glucose (corn syrup, molasses, etc.), or of glue or gelatine, helps greatly to protect these fibres from the action of the chemicals. But even when dyed with great care, using glucose, and dyeing the goods for but a short time in a bath strong in color but weak in alkali, the results are not very satisfactory, so far as shade and lustre are concerned. They have the advantage, however, of being extremely fast to washing, more so, even, than the Salt colors. In general, however, silk should be dyed with the Acid colors for ordinary work, and with the Salt colors when fastness to washing is required. The Sulphur colors should be reserved for cotton and linen. On mercerized cotton and artificial silk these dyestuffs take easily and well, when dyed in cold or lukewarm baths. The lustre, however, of the finished goods is apt to be less than when Salt colors or Basic colors are used. DYEING DIRECTIONS For cotton and linen, measure out the color and dissolve it in hot water to which has been added twice its amount of sodium sulphide (crystals) and a quarter or third the amount of soda ash. (In all these formulæ washing soda may be used in place of soda ash—only in quantities almost twice as large.) It is advisable, though not absolutely necessary, to add also to the dye-bath one or two tablespoonfuls of Turkey red oil—a kind of liquid soap made by treating castor oil first with sulphuric acid and then with soda. This prevents the formation of a dark scum on the surface of the dye-liquor, which is likely to cause streaks in the finished goods, hard to wash out. Into the dye-liquor immerse the well-wetted goods, and heat them, turning them constantly, and keeping them as far as possible away from the air and under the level of the liquid. Just before the boiling point is reached take out the goods, and add salt in the proportion of, say, two spoonfuls of salt for every teaspoonful of dyestuff used. Stir till the salt is all dissolved, put the goods back, and continue to turn them as before, keeping the goods down under the liquor and not allowing it to boil.