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DYEING AND CALICO PRINTING.
into its component parts, viz., glycerin and fatty acids. The oil so modifiedis adapted for Turkey-red dyeing. The textile fabrics saturated with theseacids are dipped in a solution of carbonate of soda,* and then exposed tothe action of the air, or air and steam, in a warm room : after this treatmenthas been repeated a sufficient number of times the goods are passed througha solution of nut-galls, then into a solution of a salt of alumina, and nextthrough warm chalk water. They are next washed, dyed by being boiled fortwo or three hours in a bath to which madder-root or garancin has been added;lastly, the brilliancy of the colour is brought up by boiling in a strong soapsolution. Up to this day no thoroughly satisfactory explanation of thereal effedt of the application of the oil in this process has been given, andsince it is an acknowledged faCt that no Turkey-red can be obtained withoutthis application, we do not enter into any speculative discussions on thissubject, but simply give a detailed account of the operations just indicated,with the observation that the processes are varied by different manufac-turers according to their own experience. The goods, first properly bleached,are padded in an emulsion made of the oil f and of an alkaline carbonate : theolive-oil applied for this purpose has the characteristic property of readilyyielding a permanent emulsion when shaken up with an alkali. The mode oftesting the oils for this purpose consists in beating up i pa^rt of oil with from36 to 40 parts of soda-lye containing about \ per cent of dry caustic soda.If, after standing for some five or six hours, the mixture is found to be homo-geneous, without any sign of a separation of the oil, it is admitted as of,fit quality. This Gallipoli oil is prepared from rather unripe olives, which aresteeped for some time in boiling water before being pressed. This treatmentcauses the oil to contain a large proportion of extractive matter.
In France the best and ripest olives yield, as is well known, a small quantityof oil spontaneously without pressure ; gentle pressure is next applied, andlastly the pressed cake is placed in boiling water for a couple of hours, andon being then pressed again, yields what is locally known as huile d'enferused for soap-making, and burning in lamps, and is very suitable for the purposeof mordanting Turkey-reds.
According to M. Persoz any oil may be rendered easily emulsive ( tournante )by beating up therewith two yolks of egg per litre. This statement does nothold good for the drying oils, since this was purposely tried several years agoby the elder M. Previnaire, at Ghent, who found that neither linseed, hemp-seed, nor poppy-oil would answer the purpose, not even when previously beatenup with yolk of eggs. This is confirmed by Professor Mulder’s extensiveresearches on drying oils, which, according to him, belong rather to the classof substances producing caoutchouc than to the true fatty oils. Accordingto the experiments made by M. E. Schwartz the action of the alkalies, prefer-ably carbonates, or even bicarbonates, is not simply to form an emulsion, butalso to predispose the oil for the peculiar changes it has to undergo afterwards.It is considered by many manufacturers necessary to add sheep- or cow-dung
* The reader will no doubt be struck with discrepancies in the details of the process ashere laid down, but there is scarcely any dyeing operation in which so many variations occur,all, however, tending to one general result.
t In Europe generally an inferior kind of olive-oil is used, but in the East (India, Persia),where the natives still produce the finest and fastest reds, many kinds of oil are used—form-stance, fish-oil, lard, and other fatty matters—very successfully.