i66

DYEING AND CALICO PRINTING .

blue, the second method is exclusively employed. It appears that wool hasa great affinity for Prussian blue when that compound is set free by heat froma solution of ferro-cyanhydric acid. The wool is therefore placed in a bath ofa solution of prussiate mixed with a suitable quantity of royal blue spirits—amixture of sulphuric, hydrochloric, and nitric acids. If the red prussiate beused the nitric acid is omitted as needless. The so-called prussiate of tin, ortin-pulp, is chiefly used as an ingredient in printing steam-blues on cotton.It is formed by mixing protochloride of tin and yellow prussiate. The lattershould be separately dissolved in one half the water, the tin salt mixed withthe other half, when both are poured together and allowed to settle. Thefollowing formulas for preparing tin-pulp for steam-blues are in actual use, andwill give an insight into its composition:—

Ordinary White Tin-Pulp.

No. 1.

No. 2.

No. 3.

Yellow prussiate of potash*

4 lbs.

8 lbs.

9 lbs.

Muriate (protochloride) of tin at 120° Baume

2 qts.

5 qts-

6 qts.

Water .. .. .

6 gals.

10 gals.

10 gals.

Yield of pulp..

2 gals.

4 gals.

6 gals.

The prussiate is first dissolved in one half of the water, the muriate of tinthen mixed with the remainder of the water; the two solutions are then mixedtogether and well stirred, to break up the precipitate into a fine pulp, theyare thrown upon a filter, or washed by decantation, and then drained down tothe given bulk.

Blue Tin-Pulp,

Nine lbs. of prussiate of potash, 5 gallons hot water, 3 quarts of solution ofbichloride of tin at ioo° B., 5 gallons of cold water. The two solutions aremixed, well stirred up with about 12 gallons of water, and then drained downto 6 gallons. In mixing dark steam-blues it frequently happens that largequantities of hydrocyanic acid are developed from the hot colours, and some-times men working over the pans or mugs are stupefied or sickened by thesmell. There should therefore always be good and efficient ventilation ; butin any serious case the sprinkling of liquid ammonia, and the inspiring ofammonia and alcohol mixed, as well as the immediate removal of the menaffeded into the open air, should be resorted to.

Among the methods in use for the production of Prussian blue by printing isthe following:—The tissue is first passed through a bath of stannate of soda,next into a bath of very dilute sulphuric acid rinsed well in water and dried,and there is then printed on it a mixture of yellow and red prussiate of potash,prussiate of tin, tartaric and oxalic acids, and sal-ammoniac. ^ The tissue issteamed and afterwards washed. Silk is dyed with Prussian blue by mor-danting with a warm mixture of nitrosulphate of iron and bitartrate of potash,or, instead of the latter, protochloride of tin. The tissue or yarn is rinsed inwater, and dyed by means of being passed through a solution of yellowprussiate slightly acidified with hydrochloric or sulphuric acid. Cotton is dyedblue also by this last method.

* We retain here the names by which in adtual practice these chemicals are known,although these names are not the most scientific.