DYEING. 



211 



Of Mor. 



danu. 



ker me- 

 thodtof pre- 

 paring it. 



in a state of combination by the acetic than by the sul- 

 phuric acid, and is therefore at greater liberty to attach 

 itself to the stuff and the colouring particles. Lastly, 

 the acetic acid being volatile, gradually separates itself 

 from the earthy basis, and thus leaves the alumine to 

 act with full energy as a mordant, without affecting 

 the colour of the colouring matter. 



212. Dr Bancroft mentions, that an acetate of alu- 

 mine may be prepared more cheaply, by dissolving 

 white lead, not adulterated by carbonate of lime, in 

 strong vinegar, and then adding to the solution a pro- 

 per proportion of alum. He found also, that litharge, 

 dissolved in vinegar, instead of white lead, was equally 

 useful for decomposing alum. The pyroligneous acid, 

 as it was formerly termed, may be substituted very ad- 

 vantageously for vinegar, to dissolve the oxide or car- 

 bonate of lead ; and the acetate of lead thus formed, 

 united with the empyreumatic oil which comes over 

 along with the acid, may be employed instead of the 

 common acetate of lead, for decomposing alum. It has 

 also been recently discovered, that lim, dissolved in 

 the pyroligneous, or other acetic acid, may be employ- 

 ed with still greater advantage for decomposing alum, 

 and forming the acetate of alumine. See Philosophy 

 of Permanent Colours, vol. i. p. 366. 



213. The solution of tin usually employed by the 

 dyers, and which they term spirit, is prepared with a 

 very dilute nitric acid, called in the language of the 

 shops, Single Aquafortis. In this state, nitric acid is 

 capable, at its ordinary degree of concentration, to dis- 

 solve about one-eighth of its weight of tin previously 

 reduced to a granulated form, by pouring it, when 

 melted, into water briskly agitated with a bundle of 

 small rods. From one to two ounces of sea salt are 

 commonly added for each pound of acid, though eome 

 prefer the muriate of ammonia (til ammoniac). The 

 acid is diluted with half its bulk of water, to moderate 

 the energy of its action with the tin : a circumstance 

 which seems to be of the utmost importance to the pro- 

 per preparation of the mordant. The solutions of tin 

 which are made most slowly, and with the least de- 

 composition of the acid, have been found to answer the 

 purpose best ; probably, as Dr Bancroft observes, be- 

 cause the tin is less calcined, or oxygenated, and the 

 solution is thus enabled to retain a larger proportion of 

 nitrogen. Two ounces of granulated tin are usually 

 allotted to every pound of aquafortis ; the tin l>eing 

 added in minute portions, and at separate intervals, to 

 prevent the solution proceeding too rapidly. The quan- 

 tity of water which is employed to dilute the acid 

 thould be carefully noted down, in order thst a suit- 

 able allowance may be made for determining the pro- 

 portion of the metallic oxide contained in a given quan- 

 tity of the eolation, which is generally one-fourteenth 

 part of the whole. 



214. Other preparations of tin have been proposed 

 nd employed as mordants. Hellot took eight ounces 

 of nitric acid mixed with an equal quantity of water, 

 and dissolved in it gradually half an ounce of very 

 white sal ammoniac, two drachms of pure nitre, and 

 afterwards half an ounce of granulated tin. Scheffer 

 dissolved one part of tin in four parts of nitro-muriatic 

 acid. Macquer dissolved three parts of tin in eight 

 parts of nitric acid, with which he mixed one part of 

 tal ammoniac and six parts of water. Pcerner put an 

 ounce and a half of sal ammoniac into a pound of nitric 

 acid mixed with a pound of water, ancf in the liquor 

 he dissolved two ounces of tin. Guliliche mixed a 



VOL. VIII. PART I. 



pound of fuming nitrous acid with a pound of water, 

 and two ounces of sal ammoniac, and this liquor he sa- 

 turated with as much tin as it could dissolve, adding 

 it by small quantities at a time. After many trials, 

 Berthollet found, that the solution which gave the most 

 beautiful colour with cochineal, both in wool and silk, 

 and which could also be preserved the longest without 

 being changed into a gelatinous precipitate, was pre- 

 pared by dissolving in nitric acid of the specific gravi- 

 ty 1.24, (water being 1,) one-eighth of its weight of 

 muriate of ammonia, adding by small portions an eighth 

 of its weight of tin, and afterwards diluting the solu- 

 tion with a fourth of its weight of water. 



215. Dr Bancroft has examined, with great care, and 

 at no small expence, the different salts of tin, and the 

 effects which they produce as mordants. We shall use 

 the liberty of giving an abstract of the results of his 

 experiments. Cochineal, with a solution 9 tin by mu- 

 riatic acid, only dyed a beautiful crimson or rose co- 

 lour ; and with a solution of that metal by a mixture of 

 tartar and muriatic acid, a beautiful scarlet. The same 

 colouring matter produced, with tin dissolved by a mix- 

 ture of muriatic and pyroligneous acid, a dark crimson. 

 Cochineal, with tin calcined by the long continued ac- 

 tion of sulphuric acid, dyed a salmon colour ; and with 

 a recent solution of tin, it produced a reddish salmon 

 colour, inclining a little to crimson. Tin dissolved by 

 the pure acid of tartar, dyed with cochineal, on cloth, 

 a very lively and beautiful scarlet, inclining a little to 

 orange. A similar colour was produced by water sa- 

 turated with cream of tartar, in which granulated tin 

 had been kept six weeks. Tin may be readily dissol- 

 ved by pure citric acid, and more slowly by lemon 

 juice. The solution, freshly prepared, dyes with co- 

 chineal a very beautiful scarlet. If it were not too 

 costly, says Dr Bancroft, this solution would deserve 

 the preference of every other for dyeing that colour. 

 Tin dissolved by the pyroligneous acid, produced with 

 cochineal a colour between scarlet and a rose colour. 

 Phosphoric acid produced a permanently transparent 

 and colourless solution of tin, which, with cochineal, 

 dyed a bright yellowish scarlet. Tin dissolved by fluo- 

 ric acid, produced with cochineal a very bright scarlet. 

 Tin dissolved by a direct mixture of pure nitric and 

 muriatic acids, in equal proportions, the former of the 

 specific gravity of 1.5, and the latter of 1.17, produced 

 with cochineal, and the common allowance of tartar, a 

 very bright lively scarlet. A similar solution, with an 

 addition of sulphuric acid equal to one-fourth of the 

 nitric, yielded only a salmon colour ; the oxide of tin 

 having been precipitated from the common dyers' spi- 

 rit by soda, and afterwards dissolved by sulphuric acid, 

 was incapable of dyeing, with cochineal, any colour 

 more elevated than orange. 



2 ifi. Dr Bancroft ascertained, that a muriate of tin, 

 containing only half the quantity of the metal which 

 the acid is capable of dissolving, operated even more 

 successfully in dyeing scarlet, than an equal quantity 

 containing twice as much tin ; and he therefore con- 

 cludes, that nearly one half the tin which the scarlet 

 dyers commonly dissolve with aquafortis, and a little 

 sea salt, is wastefully employed; a fact, he adds, which, 

 considering the increased price of tin, may, by proper 

 attention, produce a saving of very considerable im- 

 portance. He found also, that the same quantity of 

 tin dissolved in muriatic acid, combined with about 

 one-fourth of its weight of oil of vitriol, forming what 

 he calls a murio-sulpnate of tin, produced excellent ef- 



Of Mor- 

 dants. 



Dr Baa. 



croft's expe- 

 riments 

 with diffe- 

 rent sate of 

 tin. 



Murio-tul- 

 pliateoftfa. 



