Page:Cyclopaedia, Chambers - Supplement, Volume 1.djvu/632

 DYE

D Y S

might appear wonderful is, that all the boiling in the world will never diflodge any of the colour from the ituft", or occa- fion its being received into the water again. It might be fuppofed that this was wholly owing to the par- ticles of f;ilts, which had been imbibed into the fluff in its prior preparation ; that thefe attracting the particles of the co- lour to the ftuff, while the water of the Dye had none of them to caufe fuch an attraction in it, they did not remain in it. But this appears not to be the cafe, but that the fluff will at- tract the colour, whether it be previoufly prepared, or the preparation and the dyeing be all one act ; fincc the dyers fome- times dye fcarlet at once in this manner, only plunging the fluff into a dye made of cochineal, a folution of tin mixed in a large quantity of water, with a fmall quantity of fal armo- niac and cream of tartar. AH thefe ingredients are mixed to- gether before the fluff is put in ; yet after it has boiled about an hour and half, all the colour is in the fluff, and the liquor is become colourlefs as water. The event is the fame in the dyes made of woad and of indigo for the dyeing blue, and in- deed in the greater part of other colours ; but as the ingredi- ents of thefe are not fo pure as the cochineal, and there are ufually many heterogene particles among them, the liquor does not become fo wholly colourlefs in thefe, as in the cafe of the fcarlet. But the dyers, who well know that fo long as there is any colour left in the liquor, (6 long the fluff will be profi- ted by remaining in it, always take fmall quantities out of it, and examining it by pouring it gently down againft the light, they know when it is that the fluff has received all the tin- cture it can, by there being no more colouring matter fufpend- ed in the Dye.

Experience fhews, that all colours do not attach themfelves with equal readinefs to the fluff, or remain equally firmly uni- ted to it. Woad, indigo, cochineal, kcrmes, and many other colours, never reach farther than the furface of the fluff. The liquor of the Dye penetrates indeed perfectly through the body of it, but the colouring particles flopping at the furface be- come entangled there, and never penetrate, at lead: not in any great quantity, to the central part, which remains either quite white, or only very flightly tinged. This however only happens to fuch fluffs as are thick, and of a very clofe tex- ture : others are coloured throughout. And this is only the cafe in regard to fome Dyes, not to all forts, fmce the moft of the wood colours penetrate wholly through the fluff" be it ever fo thick, and colour it equally every-where. Whence it feems probable, that the colouring particles of the woods are either more minute and fine, or much more intimately blend- ed with the water, than thofe of cochineal, indigo, and fuch others as do not penetrate beyond the furface. It might feem flrange, that the fluffs which are thus readily coloured on the furface, fhould not afterwards, by the conti- nued boiling of the water, have the colouring particles car- ried farther down into the body, as the water continu- ally penetrates the whole from each furface to the center, and might naturally be expected to carry a part of the colouring particles in along with it. But if we confider the whole pro- cefs from the beginning, we find that the colouring particles are ftrongly attracted by the fluff, and fcarce at all by the water. Whence they almoft immediately leave the water, and attach themfelves to the firft part of the ftuff they come in contact with, which is its furface; and when once fixed there, it is no wonder that the particles of water, ever fo long palling by them, do not attract or take them away from this furface, as they muff do in order to carry them in ; fmce we have before had proof, that their attraction to the water is greatly weaker than that to the fluff. And the difference be- tween the wool and the cotton, the one receiving, and the other not receiving at all the coloured particles in its natural ftate, or with the fame impregnation by means of which the other does, feems refolvable into the fame principle, that tho' the attraction in wool be much greater in regard to the co- loured particles than that of the water, and therefore it robs the water of them ; yet the attraction in cotton being ltfs than in water, the colouring particles remain in the water without any tendency to attach themfelves to the cotton. In dyeing, the ingredients ufed for the colours are well known to be of very different kinds. Some of them are fuch as com- municate a colour, which will a long time refift the injuries of the air, and thefe are therefore called the good or {landing colours ; and there are others which the bare expofition to the air will deflroy or deface in a very little time, thefe are there- fore called the falfe or fading colours. In what manner is the action of the air upon thefe laft to be explained ? Does it take away, or carry off from the fluff', the very particles of the co- lours ; or does it only break and deflroy that beautiful and regular texture of each particle on which the colour depends ? The dyers very often have recourfe to feveral ingredients, in order to produce one colour ; and reafon feems to urge, that one of thefe falfe or fading colours might be rendered lafting by

mixing it with a permanent one: the dyers are alfo of th' opinion. But it is neverthelefs a wholly erroneous o " for repeated experiments have proved, that one of thefe fal? colours fades as foon, when it is mixed with a Sanding or 1 ft ing colour, as when it is ufed alone. There are but few ~ lours on which this experiment can be tried, fo as to c to a regular deciiion. One of the principal is the mixinfe"! blue and a yellow, for the producing a green. In t hj s expe- riment, if the blue and the yellow be both landing or perma- nent colours, the fluff will perfectly hold its colours, and Ki c " ceed alike, whether it be ^teffiflft blue, and afterwards yell low ; or firft yellow, and afterwards blue. But if one of the two colours be a falfe or fading colour, it is found that the green produced by the mixture will not ftand, tho' the other be ever fo good or permanent a colour.

There is a {horter way of trying the permanence of many co- lours of this kind than that of expofing them to the air, fmce in boiling only five minutes in a pint of water, in which there has been diffolved half an ounce of alum, they will lofe as much colour as they would have done by being expofed two days to the air in fummer. Some colours require different me- thods of trial, but this ferves for almoft all. The fhades of blue yellow, red and green, purple and green, are the fineft co- lours to experiment thefe things upon, as the fame previous preparation or impregnation of the ftuff ferves for both, and both depend upon blue for their bafis, the purple bein^ made of blue and red, and the green of blue and yellow. It fhould not feem furprifmg, if the fluff be firft dipped into a Dye of a Handing blue, and afterwards into a fading red' or yellow, to turn it green or purple, that the aflion of°the air, or boiling in alum water, fhould carry off thofe falfe colours, which had only been applied to the fluff after it was before fa- turated with a flanding colour. But it might be expe8ed, that when the fluff was firft impregnated with them, and af- terwards had the blue added upon them, that either the blue muff be the colour that went off, or that they muff, all re- main. But, in effect, nothing of this difference is found, but the blue remains, while the fading colours go off, however or in whatever manner or order they are applied. Mem. Acad.


 * Scienc. Par. J737.

DYKE- Reeve, a bailiff or officer, that has the care and over- fight of the Dykes and drains in deepening fens, fcfe. We find mention made of this officer anno 16 and 17 Car 2 c 11

DYSENTERY fCyc/.) — In this diforder, fome, after bleeding and vomiting, give their patients fmall dofes of calomel once a day, till their breath begins to be tainted ; the purging being moderated by opiates, glutinous food, drink, and anodyne glyfters, which is the more neceffary, as the guts in this cafe are eafily irritated. Medic. Eff. Edinb. abridg. Vol. 1. p. 72. The vitrum antimonii ceratum has been found a moft efficaci- ous remedy in this diftemper. See the article Vitrum rfhti- tnanu ceratum.

Repeated dofes of ipecacuanha, and of rhubarb with calomel, with opiates in the evening, have alfb been found fuccefsf'ul. Medic. Eff. Edinb, abridg. Vol. x. p. 65. where it is obfervedj that aftringent medicines, without gentle revulfions and eva- cuations, generally retard the cure.

Ipecacuanha and thefimarouba have often had great effects in this diftemper. See Jujfieu in Mem. Acad. Scienc. ann. 1729. This gentleman fays that the fimarouba may be compared to, and fubftituted for the macer of the antients, which is by fome fuppofed to have been a fpecific in this diftemper. See the ar- ticle SlMAROUBA.

Jo. Ge. Henr. Kramerus affures us, we may depend on the fame effect in the cure of a Dyfsntery, from the decoction of common millet feed, called St. Ambrofe's fyrup, as is promifed from the fimarouba by Mr. Juffieu. Med. Eff. Edinb. Dr. Killner tells us of two people, who were cured of an epide- mic Dyfentery by violent drubbing. Ait. Acad. Nat. Curiof Vol. 4. Obf. 113.

DYSESTHESIA, in medicine, is ufed for a difficulty of, or fault in fenfation. Blancard, Lex. Med. in voc.

DYSEPULOTICA, in medicine, great ulcers beyond cure. Id. ibid.

DYSOREXIA, in medicine, a want of appetite, proceeding from an ill difpofition, or diminifhed action of the flomach Id. ibid.

DYSPEPSIA, in medicine, a difficulty of digeftion in the flo- mach and guts. Id. ibid.

DYSPHONIA, in medicine, a difficulty of fpcech from an ill difpoficion of the organs. Id. ibid.

DYSPNOEA, in medicine, a difficulty of breathing wherein the breath is drawn often and thick, occafioned by the fluf- fing of the lungs. Id. ibid. See Asthma, Cycl. zndSuppl.

DYSTHANATOS, a word ufed by the antient writers fome- times to fignify any difeafe which occafions a painful and flow death, and fometimes for the perfcm dying in fuch a lingring manner.

E.