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DYEING AND CALICO PRINTING.

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The mordanted and aged cloth is passed into weak and hot solutions of theabove-named substances, with the view of fixing thoroughly the mordant inthe cloth and removing any excess that may have been used, without allowingit to fix itself on the white parts. By the introduction of these dung-substi-tutes and improved vats a great saving of time, labour, and expense has beeneffected. On the Continent bran is also used as a substitute for dung. Itcontains a large amount of alkaline and alkalino-earthy phosphates, while,moreover, the ligneous particles and other organic matters insoluble in watergive this substance some resemblance to dung in its mechanical action. Ithas the great advantage of not containing colouring matters, and is therefore,for light shades, preferable to dung. From 50 to 60 litres of bran are used tosome 3000 litres of water. The salt known as dung-substitute, chiefly made ^

and used in this country, is either phosphate of soda and lime or the arseniateof these bases. From 50 to 80 grms. to the hectolitre of water are used.

There is a difference of opinion as regards the good results obtained bythese substitutes; experience proves that in the case of the best dung sub-stitutes a final turn in cow-dung before dyeing is advantageous, it beingbetter for the mordanting oxide that it should go into the beck in a partlysaturated state than in a state of the highest activity. In a majority of casesthe colours will be more solid, brighter, and faster when the combinationbetween the mordant and the colouring matter is slow and gradual than whenit is rapid. Generally we may state, that with the same mordant, the dungsubstitute gives rise to the production in the dye-beck of far deeper shadesof colour than when cow-dung is used. This is readily explained by themore complete saturation of the mordants, when the substitute is used, andthe consequently smaller proportion of mordant detached from the cloth. )

The following substitutes for finishing off the fixation of the mordants havebeen proposed:—Ammoniacal gas (M. Wessorling) for purples, alkalinebicarbonates, silicate of soda. This last substance has almost entirelytaken the place of dung, and since experience teaches more and more theprecise conditions how and where to apply it, it has even come into use whereits utility was most doubtful. Its mode of action is essentially saturating; itfixes all the alumina of the mordant by causing its precipitation in and onthe fibre before it has time to become detached. The following brief de-scription of the mode of applying the silicate in madder work will give thereader some idea of its use, with the observation that the prescriptions in thisinstance, and likewise as regards all mordants and other matters of this kind,although they be fit for actual use on the large scale, are not to be consideredas given for pra&ice, it being a well-known fa< 5 t that every manufacturer has toconsider his own peculiar arrangements and situation as well as the style of workhe cultivates. The goods pass in two minutes’ time through two troughs ortanks, the contents of which are heated to 50 0 —122 0 F., and each containing— >

for goods mordanted for brown and red, black and red, brown only, red only,and rose upon a white ground—2800 litres of water and 85 litres of silicateof soda at io° B. (sp. gr. i’075). When only mordanted for purple and black,black only, and purple only, the contents of the tank are—2800 litres of waterand 60 litres of silicate of soda of the above-named strength. If it happenthat by this treatment the colours are too deep after dyeing (a small patternmay be easily tried, of course, in the dye-beck), the goods should be dunged