The kind of vinegar usually used in catsup is the strong distilled vinegar—about 100 grain, which contains 10 per cent of acetic acid. The stronger the vinegar, the better, as the weaker vinegars require too much volume to be handled, and dilute the catsup too much when they are added. Most manufacturers buy their vinegar in barrels. However, some of the larger ones have it shipped in tank cars from which it is pumped at the factory into a large storage tank, and siphoned off as needed. This is the better way when it is used in large enough quantities to warrant buying it in this manner. Barreled vinegar often contains very finely divided charcoal, which is sometimes hard to strain out; the barrels are often full of nails from which the vinegar dissolves iron, and this iron, in combination with the tannic acid of spices, produces a chemical compound (iron tannate) which is as black as ink; and sometimes the barrels contain some foreign liquid, which was left in them when they were filled with vinegar. The use of barrels also requires a lot of handling, and the waste by evaporation through the wood is considerable when the vinegar is held over a long time. One might imagine that the evaporation from a large storage tank would be greater than from barrels. However, such is not the case, as there is much more surface per gallon for evaporation in the barrel than in the large tank. Vinegar shipped in tank cars is free from contamination and is easily and economically handled. Barreled vinegar should always be strained through fine cheesecloth. Transference of Vinegar The use of steam pumps and ejectors, in fact any kind of steam appliance for hoisting vinegar, should not be used, as the steam passes into the vinegar, dissolves in it, and dilutes it. If you pump 100–grain vinegar into a storage tank with a steam pump you may find that you have 90–grain when you get it up there. If it is necessary to pump the vinegar, and it usually is, a small electric pump should be used. Either enamel lined or wooden pipe should be used for vinegar. All iron pipe and fittings should be eliminated. Adding the Vinegar Vinegar should be added about three minutes before the batch is done. To do this it is usually necessary to cook the catsup just a shade heavier before the vinegar is added than it will be when it is done. If a hydrometer is used, about two degrees is enough. Five minutes should be the outside limit for cooking the vinegar. Vinegar is a volatile liquid and vaporizes rapidly. It should therefore only be cooked long enough to insure its being thoroughly incorporated in the catsup, and three minutes boiling is ample for this purpose. For a 100–gallon batch, 10½ gallons of 100 grain vinegar is about the right amount, and when properly added will give an average total acidity of about 1.25 per cent calculated as acetic acid. Acidity