A large quantity of the B. sent into market has more or less common salt added, for the purpose of preserving it. For use within a week or two, the proportion of common salt employed is about an oz to 2 lbs. of B., though, where it has to be kept for some time, as much as 1 oz. of salt to 1 lb. of butter is used. The incorporation requires to be carefully and dexterously done, so. that the resulting material may be uniform; and the better plan is to add only a portion of the salt at a time, and to knead and re-knead the B. till the whole is thoroughly mixed. When the less amount of salt has been employed, the result is powdered B., and the larger quantity yields salt butter. Much of the latter is closely packed In small wooden firkins or kits, and occasionally in stone ware, and sent into market. Great care must be taken to have these kits, and indeed to have every vessel used in the preparation, as clean or sweet as possible. Constant rins ings with cold water, and scaldings with boiling water, are resorted to Attention must likewise be paid to the air of the apartments in which the operations ate carried on, as a tainted air is very injurious.
The adulterations liable to be present in B. are an undue proportion of salt and water, and these run up occasionally to upwards of 33 per cent, or one third of the total weight. Another adulteration is the presence of lactate of zinc, derived from the milk being placed in zinc pails and basins, from the impression that by sonic imaginary electrical influence an increase in the amount of cream will be the result; bat though this is not attained, yet the milk tending to form lactic acid, the latter attacks the zinc vessel, and forms lactate of zinc, which dissolves in the milk, and thereby contaminates it, imparting an unpleasant taste, and, when present in larger quantity, leading to violent spasmodic vomiting. When B. is allowed to get old, it becomes rancid and tastes and smells disa greeably. To some extent an acid is formed, called butyric acid (q.v.). For the use of B. in diet, see Foot) and Ntrrumon • •