When wash is distilled in the ordinary simple or pot still, the first part to come over consists of the very volatile matters,--more volatile than alcohol even,--that is, the ethers mixed with some alcohol. This is known as the fore-shot or first runnings, and is collected separately. When the spirit coming over possesses no objectionable odor, the second stage has begun. This running would be of the alcohol proper, getting weaker and weaker, however, as the running continues and this would be caught separately as long as it is of sufficient strength. At last would come the weak spirit containing much fusel oil. It is to be understood, however, that there is no defined line between these divisions. They graduate one into the other. The first and last runnings in the old practice were mixed together and distilled with the next charge. When a strong spirit was required, rectification would be repeated several times. It is customary, however, with the improved modern apparatus, to produce at the outset spirit containing but little fusel oil and at least 80 per cent of alcohol. This is then purified and concentrated in the above manner and afterwards reduced with water to the required strength. Another cause of the offensive flavor of the products of distillation is the presence of various acids, which exist in all fermented liquors; they are chiefly tartaric, malic, acetic, and lactic acids. The excessive action of heat upon liquors which have been distilled by an open fire has also a particularly objectionable influence upon the flavor of the products. The first operation in the process of rectification is to neutralize the above-mentioned acids; this is effected by means of milk of lime, which is added to the liquor in quantity depending upon its acidity; the point at which the neutralization is complete is determined by the use of litmus paper. In the subsequent process of distillation, the determination of the exact moments at which to begin and to cease collecting the pure spirit is very difficult to indicate. It must be regulated by the nature of the spirits; some may be pure 20 or 30 minutes after they have attained the desired strength; and some only run pure an hour, or even more, after this point. The product should be tasted frequently, after being diluted with water, or a few drops may be poured into the palm of the hand, and after striking the hands together, it will be known by the odor whether the spirit be of good quality or not; these two means may be applied simultaneously. [Illustration: FIG. 35.--Rectifying Still.]