The majority of the recipes for carmine, which are frequently sold at a high price, differ but little from the above; acid potassium tartrate is used instead of the oxalate, but the latter is to be preferred because of the slight solubility of the tartrate. It is important not to use too strong decoctions of cochineal, and to add only small quantities of alum. The clear liquid is placed in shallow glass dishes. After a few days the nature of the deposit should be examined: if a considerable quantity of a red precipitate has formed, the liquid is poured off into other dishes, in which carmine again separates during the following days, and usually of a brighter colour than the first. For example, 125 grammes of cochineal are boiled with 5 litres of water during fifteen minutes, 30 grammes of very finely powdered alum are added to the boiling liquid, which is again boiled for a few minutes, allowed to clarify and cool. The greater part of the carmine is then obtained in a few hours, but the liquid still separates carmine after several days. According to another formula 500 grammes of cochineal are boiled with 30 litres of water, 60 grammes of cream of tartar are added, then 30 grammes of alum, boiling is continued for several minutes, and the liquid then allowed to cool. Carmine may be obtained in a very short time by means of tin solution. The process is similar to that just given. The liquid which would be set aside for the spontaneous deposition of the carmine is, however, returned to the pan, and a solution of pure stannous chloride added in drops, so long as the solution is still clearly red. The carmine separates at the bottom of the pan; the liquid drawn off, even when it appears almost colourless, produces a further small quantity of carmine in a few days. According to J. J. Hess, a brighter carmine is obtained when the fat of the cochineal is previously extracted by ether or benzene. Proposals have often been made to deepen the colour of prepared carmine; this must be done with the greatest care, for it is very easy to produce a less handsome instead of a finer pigment. The carmine is moistened with distilled water containing about 5 per cent. of ammonia solution. Carmine readily dissolves in ammonia. This property may be applied to test its purity, pure carmine should dissolve without residue in 5 to 6 times its quantity of ammonia. Any considerable residue denotes an intentional addition of some adulterant. Starch, vermilion, and cheaper lakes are used for this purpose. The red solution obtained by treating carmine with the above quantity of ammonia may be used as a red ink. This solution can also be used to purify carmine; when it is allowed to stand in an uncorked bottle for some time the ammonia escapes, and the greater part of the carmine is deposited as a very fine powder.