For this colour the common boiling is enough, the silk is alumed the same as for fine scarlet, washed and twice beetled. Thus prepared, two ounces of cochineal are given to it, with the same precaution as usual, but no composition nor tartar. Being worked moderately warm, in working it must be expeditiously turned; after a quarter of an hour the liquor should be brought to boil, when the turning need not be so expeditious, but it should, nevertheless, be continued for two hours. After being washed the silk is dipped in the vat, more or less strong, according to the shade required. Washing and drying are done in the same manner as for blues and greens, and in general for all colours _dipped_ in the vat, namely, a small quantity at a time, in order that the silk may be kept open to the air, and that the greening of the vat may pass correctly and equally to blue. For some shades archil forms a part of this dye. For other _violets on silk_ see Chapter III. _Observations on_ CRIMSON _and_ SCARLET _upon silk_. Crimson upon silk is produced at Norwich, London, and many other places, by using a much larger quantity of cochineal than that which is directed by Macquer: for in some cases, as much as a guinea a pound, has, it is said, been paid for dyeing silk crimson at Norwich. Archil has been used, likewise, in crimson, and the time of boiling is not so long. In some shades a little of the composition and tartar may be admitted, but in a small degree. It should be stated, however, that _scarlet upon silk_, is often done by annatto and safflower. _Observe_, that although we have given the preceding processes for crimson and scarlet, yet many others might be mentioned. What has been said in regard to _dyeing scarlet on woollen_, (page 85.) should also be carefully attended to, particularly relative to the conversion of scarlet into crimson by alum, soap, and the alkalies. And though we have given directions for the preparation of a _nitro-muriate of tin_, yet pure _Muriate of tin_ is now very often used for dyeing silk red. MR. M'KERNAN, gives us the following process for preparing it: Take of fine muriatic acid, of the specific gravity of 1.120, two quarts; add by degrees, one ounce at a time, of feathered tin, for twenty-four hours. Put the vessel in a sand heat and bring it gently to boil, observing to add more tin as that in the acid becomes dissolved. There should be some tin left undissolved when the liquor is cold, thus indicating that the acid is perfectly neutralized by the tin. Bottle for use. _On dyeing silk_ GREEN. This colour is composed of _blue_ and _yellow_. It is with difficulty produced on silk, because the blue vat is liable to spot and give a party colour, an inconvenience to which green is more liable than blue, and more perceptible. The boiling of silk for greens is the same as for common colours.