The above experiments showed that the cloth, when boiled with the strongest eolutiona either of carbonate of soda or caustic soda, dyed up deeper and redder in the madder bath than when boiled with the weaker solutions, and proved that whatever the proportion of aoda used it is not able to remove that principle in the cotton fibre which attracts the dye in a madder bath. This result was completely confirmed by experiments made on the large scale, taking 2800 lb. cloth, and 50 lh., 100 lb., 150 lb., 200 lb. soda ash (without reain) for four aeparate trials.
If, in any of the foregoiog experiments, a little resin aoap was added to the aoda boil, it waa found that after chemieking, souring, and washing, the cloth no longer dyed in a madder bath, but became merely auperficially soiled and tinged of a delicate pink shade. The reain soap, added to the soda, seems therefore not only to diaaolve off better the free fatty acids; but alao to diseolve off that waxy, resinous, or albuminous principle which attracta the dye of the madder bath, and which a boiling in soda alone does not affect.
3. Iu order to determine the best proportion of reain to employ, the following trial was made. Cloth which had been previously limed, soured, and washed, waa divided into four fenta, and each was boiled aeparately for 12 hours with the following eolutions of resin and soda in 1 gall. water :— a. 1 oz. soda, oz. resin.
c. 2 oz. soda, 2 oz. resin.
b. 2 oz. soda, 1 oz. resin. d. 4 oz. aoda, 3 oz. resin.
The fente were then boiled for 1 hour in a solution of 2 oz. soda per gall. water, waahed, chemicked, aoured, waahed, and dyed with madder. Results : a waa a pretty good white, b and c were the beat white, d was brownish, not a good white. These were corroborated by experimenta made on the large scale with 2800 lb. cloth. If 50 lb., 60 lb., 62 lb. reain were used, the dyed white was good, while the use of 75 lb., 80 lb. and more resin gave a dirtier and browner white after dyeing.
The final operationa of the madder-bleach, viz. Squeezing, Opening, and Drying may now be discusaed.
Squeezing.—The squeezing rollers or "equeezers,'' for expressing the greater part of the water retained by the piecea from the final washing, are repreaented in Fig. 350. Thia machine consists of a pair of hard wooden bowls or rollers A A, generally of birch or aycamore, about 18 in. or more in diameter, and about 18 in. in length ; sometimes the bottom bowl ia made of highly com pressed cotton. Compound levers, weight, and screws B B and C aerve to regulate the presaure of the bowla againat each other ; the latter are driven by cog-wheels connected with shafting, or preferably by an attached independent small engine. The pair of bowls are usually aet over a small water
trough D D, through which the piece passes before entering the nip. Through this machine also, two lengths of piecea generally pass at the same time, not spirally, aa in the washing machinea, but each getting only a single nip. One of the principal drawbacka in this squeezer is the com paratively rapid destruction of the bowls, the attendant inconvenience of atoppage, and the expenae of renewing or turning up the bowie in a lathe.
The above form of equeezer ia being rapidly auperseded by the more durable one introduced by Wm. Birch. The elasticity of the rollers, so indiapensable when the cloth atrand is spread out in a flat layer of necessarily uneven thickness, becomea superfluous when the atrand is confined in a narrow groove, in which the layer of cloth must needs arrange itaelf evenly. This grooved form ie the one adopted by Mr. Birch, the rollers being of brass, a material far more durable, of cuurse, than wood or other elastic substances. Thia form of roller has further the very important advantage that the even layer of cloth thus obtained in it permits a reduced pressure to be used, since all the parts of the layer are evenly affected and do not, as in the above-mentioned squeezer, necessitate au over-pressure for the thick central part in order to get some little for the thin sides.
For thin material, however, Birch's machine is not adapted, unless two or three pieces can he run together, since there must be at least inch thickness of material to form a pulpy cushion at the bottom of the groove, otherwise the cloth will be cut. Fig. 351 represents this improved machine. T is a water trough through which the piece passes as it cornes from the final washing, passing thence between the two brass rollers R R, the upper one of which simply rests on the lower ono with its own weight. The use of these rollers is to express the excess of water, and to prevent its being carried round by the velocity of the squeezing rollers themselves. From these rollers, the piece passes over the wooden roller D, and enters the deep groove of the roller A, at the bottom of which it is pressed by the disc roller B; S is the spring for exerting the pressure of the diso roller in the groove ; P and DI are pulley and driving belt.