OUR YORKSHIRE LETTER

Otago Witness, Issue 2600, 13 January 1904, Page 8

OUR YORKSHIRE LETTER

(From Our Special Correspondent.) BRADFORD, November 13. SULPHUR IN WOOL.

Sheep dips containing a lot of free sulphur should be entirely discarded, and cheep farmers sj ould use only those sheep dips whioli are known to be properly and scientifically compounded One sf the annoying things that is ap' to be present in all wool is a certain proportion of sulphur. It may not be present in a very large quantity, but whenever it is in evidence, it loads to complications and trouble of various sorts. At the start, perhaps the- first thing to determine is whether there is sulphur precezit at all or nob, and this can be done by means of the following simple tests. Take a solution of oxide ot lead dissolved in neutral acetate of lead solution, dilute it, and rake it to the boiling point, and; then place the wool to be tested in this dilute boiling solution. It will he noticed that the wool will first turn tc a brown colour, and then finallj to a black, and the lcasoc for this is that the lead of the solution has combined with he sulphur of the wool in the form of a lead sulphide, and this has become a precipitate upon the wool fibre. The combination forme a black lead sulphide, and ithis sulphide will not be produced unless eulphur is present, so that it is possible to use this teat if it is desired to determine whether a fibre is really wool or not. A wool treated thus will show the black precipitate, while if the fibre is eilk or some other material, no such, preoipitate will form, because eulphur is not a chemical that is found on -any other textile fibre than wool. It may vary from 1 to 4- per cc-nt. in wools, and so can eauso trouble if it is not removed.

It jiight- be thought that sveh a small proportion of sulphur as the above could cause no appreciable difficulty in the finishing and wool treatment processes, but such is a serious mistake. The fact is that whr-n culphur appears on the wool fibres, and is not removed, it is bound to lead to trouble,, annoyance, and difficulty. In the dyeing of wool* it is well (known that if sulphur is present there ie liable to be great difficulty with light shades and colours. In cases of this kind it is impossible to use metalli dye kettles, because, the sulphur on the wool will combine with the metal of the kettle to form a dark-coloured precipitate that will cause more or Ics3 variation in the shade of the colouied fibre, according to the proportion of sulphur present and the kind of metal in the containing vessel. Tremble of this description is suie to result when the neutral dye kettle ie used, and if copper or lead is the metal in the kettle. It will be noticed that the same result praoticallj follows in this case as followed in the test above described for the detection of sulphur in the wool. The trouble in both cases arises from the formation and precipitation of a dark-coloured sulphide upon the fibres of the wool. The trouble is most marked where the colour or shade is delicate, and the sulphur is present in the larger proportions. Practically similar results are caused from similar conditions in the wool mordanting operation, unless care and caution are exercieed. It too much of the crystals of tin are used in the mordanting treatment o f a wool from which the sulphur has not been removed, the result will bo that the sulphur of the wool will combine with the excess of tin in the mordant, and a metallic eulphate will again Ix produced which will precipitate on the fibres of the wool in the form of a dark-coloured material, which will turn the wool brown ir colour. This, of course, will :ause> infinite trouble if the

wool i 3 one ihat has fo te dyed a light shada or colour. In fact, In order to dye li'jht and delicate shades it '3 practically necessary by earns moans or other to remove the sulphur from the- wool before the drying is undergone. In order to remove the sulphur which is found on wool fibres a chemical process is necessary. ThLj pioeess can be employed without any injury to the wool fibre as far as practical purpopos are concerned, yet it might be well to state that to remove absolutely all trace* of the sulphur by chemical means has been found impossible to accomplish without resulting in some serious detriment and injury to the structure of the v. 00l fibre. Thus fact is one that make? this whole matter one of importance and far-reaching in its consequences. It is eloubtful if dyers fully appreciate the need of care and treatment in this particular respect, and colours off shade, and lacking in brilliance and effectiveness, may frequently bo due to laxity a-nd neglect in this particular.

Ifc is possible to reduce- (he proportion of sulphur present in the wool to about onehalf of 1 per cent, by chemical treatment, and when the proportion is so low it practically has no effect and cannot combine with metals in containing vessels or in mordanting liquors, and so form, eulphides which lead to "variations in colour and shade. In order to reduce the sulphur io this proportion the plan is to steep the avool for a day in a dilute bath of mi'k of lime. After this treatment for 24 hours, the wcol is acidulated with hydrochloric seid, and the process is completed by means of a thorough and perfect wa c hing and ihising in. clear, clean water. Thus the sulphur is reduced to a mimimum, and little difficulty need be feared in its after treatment in colouring or finishing.