"If a solution of 1,369 per cent, of caustic ammonia is added to this red fluid, and the tube is turned around to effect the necessary mixture, keeping its mouth closed with the thumb, after the addition of more or less of the ammonical fluid, it will change into violet. This tinge indicates the saturation of the acids, and the height of the fluid in the tube now shows the quantity of acid in the must, by whole, half and fourth parts per cent. The lines marked 1, 2, 3, 4, indicate whole per cents.; the short intermediate lines, one-fourth per cents." [Illustration: FIG. 33.] When DR. GALL, shortly before the vintage of 1850, first publicly recommended the dilution of the acids, he was obliged to refer to this instrument, as already known, and everywhere at hand, which was at the same time cheap, and simple in its use. "It is true, however, that if must is examined by this instrument, the quantity of acids contained in it, is really somewhat larger than indicated by the instrument; because the acids contained in the must require for their saturation a weaker solution of ammonia than acetic acid." As however, OTTO'S acidimeter shows about one eighth of the acids less than the must actually contains, and about as much acids combined with earths is removed during fermentation, DR. GALL recommends that the quantity of acids be reduced to 6-1/2, or at most 7 thousandths of OTTO'S acidimeter, and the results have shown that this was about the right proportion; as the wines in which the acids were thus diluted were in favor with all consumers. "The acidimeter referred to was afterwards improved, by making the tube longer and more narrow, and dividing it into tenths of per cents, instead of fourths; thus dividing the whole above 0 into thousandths. But although by this improved acidimeter the quantity of acids could be ascertained with more nicety, there remained one defect, that in often turning the glass tube for mixing the fluids, some of the contents adhered to the thumb in closing its mouth. This defect was remedied in a new acidimeter, invented by Mr. GEISLER, who also invented the new vaporimeter for the determination of the quantity of alcohol contained in wine. It is based on the same principle as OTTO'S, but differs altogether in its construction. It is composed of three parts, all made of glass; the mixing bottle, Fig. 34; the Pipette, Fig. 35; and the burette, Fig 36. Besides, there should be ready three small glasses--one filled with tincture of litmus, the second with a solution of 1,369 per ammonia, and the third with the must or wine to be tested; also, a taller glass, or vessel, having its bottom covered with cotton, in which glass the burette, after it has been filled with the solution of ammonia, is to be placed in an upright position until wanted. [Illustration: FIG. 34.] [Illustration: FIG. 35.] [Illustration: FIG. 36.]