41
No. 3 clouds at 175°, and gelatinizes at 192° (80°,89° C.); the cloudiness disappears on cooling, andis entirely prevented by an excess of alumina in thesolutions. According to the experiments of Koch-lin Schonoh, it appears that the activity of the redliquor is not wholly dependent upon the amount ofaluminium acetate which it contains, since a portionof the salt is converted into a basic sulphate whichcombines with the triacetate and constitutes the truemordant.
When used by the calico-printer the red liquor isthickened with gum or some other suitable material,and with it the design is impressed upon the clothby a wood block, or by any other means; on sub-sequently submitting the goods to the drying-bath,acetic acid is partly volatilized, and the aluminousbasic compound remains perfectly combined withthe cloth.
It is immaterial, as to the effect on the texture,and the beauty of colour produced on the cloth,whether 100 lbs. of alum be decomposed by 125 or75 lbs. of acetate of lead, since the aluminium acetateacts by giving up its base to the fibre of the cloth,and this is effected as well when a basic sulphate ofthe earth is present as when it is wholly in the formof a sesquiacetate. Eunge differs from this view;by his experiments he endeavours to show that thequantity of acetate of lead should be always 120 lbs.to every 100 lbs. of alum, and that even the amountof water employed affects the quality of the product.He based equal weights of cotton fabric in eafch ofthe following solutions, made by adding—•
100 lbs. of alum,
75 lbs. of acetate of lead, and
280 lbs. of water together, agitating the mixture, andfiltering ;
Secondly, by dissolving—
300 lbs. of alum in
448 lbs. of water, and adding
120 lbs. of acetate of lead in powder, agitating themixture, and filtering off the clear liquor asabove.
The fabrics being allowed to remain in an equalmeasure of these solutions for the same time, anddried at the same temperature, were washed withequal quantities of hot water; the washings fromthe cloth mordanted in the first solution containedmuch alumina, while only very slight traces wereindicated by the washings from the cloth steeped inthe second solution. He did not, however, take intoaccount the neutralization of a part of the sulphuricacid by carbonate of soda, which, by bringing basic
salts into action, materially changes the reactionwhich takes place during drying, and undoubtedlyfixes a much larger amount of alumina in the fabricthan would otherwise be the case. And although aportion of this alumina may be washed out afterdrying, it is questionable whether the advantage ofusing so large a proportion of lead acetate is notcounterbalanced by the greatly increased cost. Theusual addition of carbonate of soda, to the extent ofabout one-tenth of the alum employed, acts advan-tageously in the manufacture of red liquor, when alow proportion of sugar of lead is used, by unitingpartly with the sulphuric acid, and producing a basicsulphate, as well as acetate of alumina, as mentionedabove.
Crace Calvert states, from practical observations,that a sulphacetate of alumina is to be preferred,as giving the most satisfactory results. lie considersthat a mordant of such a composition is the bestadapted for fixing the colours, on account of theexcess of alumina in such a solution, above thosewhich contain, besides the aluminous salts, salts ofthe alkalies, which are inert in the uses for whichred liquor is manufactured.
The preceding he prepares by mixing together—
453 lbs. of ammonia alum,
379 lbs. of lead acetate, and1132 lbs. of water;
or,
or,
383 lbs. of aluminium sulphate,
379 lbs. of lead acetate, and1132 lbs. of water;
453 lbs. of alum, and a quantity of solution of acetate oflime, amounting to 158 lbs.;
333 lbs. of aluminium sulphate, with the same amount ofacetate of lime solution.
On agitating the foregoing mixtures, decompo-sition takes place; sulphate of lead or of lime isthrown down, and a sulphacetate remains, with anequivalent of ammonium sulphate from the ammoniaalum. Instead of alum, many printers now usealuminium sulphate—
Ar 2 ‘(S0 4 ) 3 + 18H s O;
or,
Al 2 0 a 3S0 3 + 18II 2 0;
in the fabrication of this mordant, which is muchmore economical, as the solution of this salt, broughtto the standard strength, or 1-085 spec, grav., con-tains more alumina than the ordinary red liquor ofthat strength, as the following analyses show:—
Alumina,...
Acetic acid,.
Sulphuric acid,.
Ammonia and w-ater,
Formula.
(NH 4 ) s S0 4 .
Formula.
A1 v ‘S0 4 2C 2 H 3 0 2 +(N1I 4 ) 2 S0 4 .
Mordant A.
Mordant 11.
Mordant C.
Grs. Oz. Grs.
Grs. Oz. Gw.
Grs. Oz. Grs.
3680-0 = 3 368
1830-0 = 4 80
3239-0 = 2 365
3369-8 = 7 307
3570-0 = 8 170
1281-7 = 2 406
2642-5 = 6 37
2800 0 = 6 175
3017-0 = 6 392
674-1 = 1 236
930-0 = 2 35
653-1 = 1 215T
Ar 2 *S0 4 ,4C 2 H 3 0 2 .
Mordant J>.
Grs. Oz. Grs.
2104-4 = 4 4143679-2 = 8 3791661-6 = 3 352