MORDANTS.

527

Nitrate of Tin, called also, from its principal use, “ Scarlet Spirits” and“ Bowl-Spirits,” because prepared in large stone-ware bowls. The namenitrate of tin, it must be remembered, is applied in some distri&s to per-saltsof tin prepared with mixtures of nitric and hydrochloric acid, in which thelatter largely predominates. The name, however, in the woollen regions ofYorkshire, and especially in the Halifax and Bradford districts, is exclusivelyapplied to the compound we are now describing. Its preparation is a matterof some nicety. A known quantity of the liquid which we have mentionedabove under the name of single aquafortis, or dyers’ aquafortis, standing at32 0 Tw., is placed in a capacious and perfectly clean bowl, and the finest grain-bar tin, in the rod, i.e ., not feathered, is dissolved therein, in the proportion of1 lb. of metal to 8 lbs. of the acid. The number of rods put in at first is varied,according to the temperature and the make of the acid. If the weather be neitherhot nor cold, and the acid of an average quality, some four or five rods are placedin each bowl, and allowed gradually to dissolve. After a time, if the operationis successful, the liquid is said to “ turn,”—that is, to assume a deep amber ororange colour. When this point is once attained, all that is required is tofeed in by degrees the remainder of the tin that has been weighed out, takingcare that the adtion neither dies out from want of material nor becomes toofierce. No bubbles of red- or orange-coloured gas ought to be formed. If theprocess is unsuccessful, the liquid will sometimes remain colourless, likewater, for two or three hours, and then suddenly become thick and turbid,without development of the amber colour. Under other circumstances, espe-cially if too much tin has been added at the outset, orange-coloured fumes ofnitric oxide are thrown off, and the tin, instead of dissolving, is deposited inan insoluble condition. In these cases the spirit is said to have “ turned itsback ” on the operator, and is hopelessly spoiled. In cold weather as manyas eight or ten rods may be entered at once without fear of accident; butwhen the temperature is high, two, or even one, may be quite sufficient, andit is sometimes needful to keep down the adtion by placing the bowl in acurrent of cold water. Sometimes, in hot weather, this spirit may be advan-tageously started with a small handful of clean, dry, feathered tin ; rods beingafterwards gradually added, when the spirit is once fairly in course of forma-tion. The operation is greatly facilitated if, at the outset, half a pint ofnitrate of tin, from a former making, is added to the aquafortis.

If properly made this spirit is a deep amber liquid, of from 58° to 66° Tw.,and contains about 2\ ounces of metallic tin to the pound. It is not an articleof commerce, being always made on the spot on account of its instability. Onlong standing it deposits its tin in a yellowish gelatinous mass, and becomesunfit for use.

Curiously enough, some persons have denied the very existence of thispreparation, though known and used in every dye-house in Yorkshire wherecochineal shades are produced. Almost the only author who admits itsexistence is J. Ordway (“ Chemical Gazette ”).

Nitrate of tin is chiefly used for grounding scarlets and other cochinealshades upon wool and worsted goods of all kinds. It is sometimes alsoemployed in cotton-dyeing, especially for the cotton warps of coburgs,delaines, and other mixed goods.