The reds are turned more yellow by nitrate than by acetate of alumina, and when the former is used more acetate of lime is taken in addition.
A solution of acetate of lime at 25° Tw. contains 25 per cent. of acetate of lime; generally 1/10th of the weight of alizarin paste is required; but with a fresh quantity of alizarin it is safer to ascertain, on a small scale, the amount needed.
13-1/4 lbs. alizarin paste (15 per cent.); 9 quarts thickening; 2 lbs. nitrate of alumina, at 29° Tw.; 15 oz. acetate of alumina, at 19° Tw.; 15 oz. red prussiate potash, dissolved in water; 1 lb. 1 oz. acetate of lime, at 29° Tw.
To obtain a yellower shade, for every quart of mixed colour, 1 oz. bark liquor, at 30° Tw., may be added.
Old spoiled red colours may be advantageously used for browns by adding per quart, 3/4 oz. to 1 oz. red prussiate, dissolved in water.
=ALKALI.= _Syn._ ALKALI, Fr.; LANGENSALZ, Ger. This word has been used in various senses, but is now usually applied to four substances only, viz. the hydrates of potassium, sodium, lithium, and ammonium (the latter being supposed to exist in the aqueous solution of ammonia). In a more general sense it is applied to the hydrates of barium, strontium, and calcium, which, for the sake of distinction, are called the alkaline earths. The following properties are characteristic of the alkalies:--(1) They are soluble in water, the alkalies proper more so than the alkaline earths. (2) They change the hue of many vegetable colouring matters; thus, they turn reddened litmus blue, yellow turmeric brown, and syrup of violets and infusion of red cabbage green. (3) They neutralise the strongest acids. (4) They precipitate most of the heavy metals from solutions of their salts as hydrates or oxides. (5) They saponify the fixed oils and fats. (6) They exert a caustic or corrosive action on animal and vegetable substances.
=ALKALI ACTS.= The principal alkali Act is the 26 and 27 Vict., c. 24, amended by 37 and 38 Vict., c. 43, the amended Act having come into operation in 1875.
Every alkali work must be carried on so as to ensure the condensation of not less than 95% of muriatic acid evolved therein; and it must be so condensed that in each cubic foot of air, smoke, or chimney gases, escaping from the works into the atmosphere, there is not contained more than one fifth part of a grain of muriatic acid. Penalty for first conviction, £50; for second and other offences, £100, or less (26 and 27 Vict., c. 124, s. 4; 37 and 38 Vict., c. 43, s. 4).