TARTAR AND ARGOLS.

549

Another portion of the solution may be mixed with a solution of nitrate ofsilver. A white curdy precipitate indicates the presence of a chloride, pro-bably common salt.

A third portion of the nitric acid solution of the sample is mixed with am-monia, and oxalate of ammonia is added. If, on stirring the mixture andallowing it to stand for a few minutes, a white precipitate is produced, lime ispresent. A small amount of lime is of course naturally present, due to tar-trate of lime. If the precipitate produced is plentiful, sulphate or carbonateof lime has been added.

Red argols are less frequently sophisticated. Both these compounds areextensively used in dyeing; the white kind for scarlets, crimsons, and othergrain-colours ; red argol is used for certain blacks and other dark shades.

White argol, dissolved, filtered, and re-crystallised, is known as grey tartar,and on still further purification it becomes white tartar. The tartars are usedin dyeing pinks, maizes, &c.

Liquid tartar, otherwise known as protartar spirits, is prepared as follows:—

Mix—Grey tartar or white argol. io lbs.

Sulphate of soda, crystals. io ,,

Dilute sulphuric acid, at go 0 Tw. 6 quarts.

Then add water sufficient to let down the whole to iy° Tw. This liquid isemployed by some dyers for “ levelling ” certain colours, especially anilineblues, upon woollen and worsted goods.

Tartaric Acid, obtained by the decomposition of the tartrates, is exten-sively used both in dyeing and printing. Sometimes it is sophisticated withbisulphate of potash. To detedt this fraud a small quantity of the sample isheated to redness upon a slip of platinum foil, or in a small platinum capsule.If bisulphate of potash is present a white fused mass will remain, but if thesample is genuine nothing will be left. Tartaric acid is sometimes used ingrain-dyeing. In printing it serves for a discharge on Turkey reds and dipblues, and in steam greens and blues it is used to decompose the yellowprussiate of potash.

A solution of tartaric acid in water is sometimes sold under the curiousname of “ essence of tartar.” Not unfrequently this “ essence ” is weightedwith sulphuric acid, which may be dete&ed by acidifying with pure hydrochloricacid, and adding chloride of barium in solution. A white precipitate showsthe presence of sulphuric acid, added either as such or as a sulphate.

Since the grape-disease first made its appearance, and since the accom-panying rise in the price of argols, tartars, and tartaric acid, a number ofcompounds have appeared in the market under such names as tartar substi-tutes, pro-argols, pro-tartars, &c. These bodies profess either to economiseor totally to replace the real substances. Some of these contain argol ortartar in various proportions ; others are mere mixtures of common salt,oxalic, acetic, and sulphuric acids, alum, &c. These substitutes may in somecases prove satisfa&ory. Certain dyers, for instance, are in the habit of usingargol, where nearly any acid would answer the end required. In such instancesthe substitutes may give satisfa&ion. But where the distin&ive properties ofthe bitartrate of potash are really needed, these pro-argols can only lead todisappointment. Some makers, however, prudently recommend that a certain