4419. Mallow Test Paper

4419.    Mallow Test Paper. Prom an infusion of the purple flowers of tho common mallow.

4420. Manganese Test Paper

4420.    Manganese Test Paper. Prom a solution of sulphate of manganese; turns black by contact with ozone.

4421. Rhubarb Test Paper

4421.    Rhubarb Test Paper. From a strong infusion of the powdered root; alkalies turn it brown, but boracic acid and its salts do not affect it.

4422. Rose Test Paper

4422.    Rose Test Paper. Made with a strong infusion of the petals of the red rose; alkalies turn it a bright green.

4423. Starch Test Paper

4423.     Starch Test Paper. From a cold decoction of starch; free iodine turns it blue.

4424. Sulphate of Iron Test Paper

4424.    Sulphate of Iron Test Paper. Made with a solution of tho protosulphate; as a test for hydrocyanic acid and the soluble cyanides.

4425. Turmeric Test Paper

4425.      Turmeric Test Paper. Prepared with a decoction of 2 ounces turmeric to 1 pint water; is turned brown by alkalies, and by boracic acid and tho soluble borates.

4426. Cabbage Test Paper

4426.    Cabbage Test Paper. Make a strong infusion of red cabbage leaves, strain it, and evaporate it by a gentle heat till considerably reduced. Then dip tho paper in it and dry it in tho air. (This paper is of a greyish color; alkalies change it to green, acids to red. It is a very delicate test; if rendered slightly green by an alkali, carbonic acid will restore the color.)

4427. Alkanet Test Paper

4427.    Alkanet Test Paper. The red principle of the alkanet root (Anchusa tinc-toria, L.) is, as is well known, a most sensitive reagent for alkalies and acids; it is used for the preparation of test paper, and is prepared like litmus paper, by saturating unsized paper with a solution of the alkanet red. This is obtained by extracting dry alkanet root with ether; the filtered liquid is ready for use. The blue paper may be obtained from the red one by dipping it in an aqueous solution of carbonate of soda of specific gravity 1.5. A paper, answering for both alka-line and acid test, may bo prepared by dividing tho ethereal solution of alkanet red into two equal parts; to one is added, drop by drop, a watery solution of carbonate of soda, until tho red just has changed to a distinct blue hue; then both liquids are mixed and used for tho preparation of the paper. This, when dried, has to be kept in tightly closed bottles.

4428. Test Paper from Hollyhock Flowers

4428.     Test Paper from Hollyhock Flowers. Some years ago Prof. Aiken, of the University of Maryland, proposed paper stained with an infusion of the petals, as a substitute for litmus paper. His althaea paper is purplish-blue when dry; acids impart a carmine hue, which is turned to bluish-green by alkalies, the neutral tint being purplish-blue; it is superior in intensity of reaction to turmeric, and quite equal to litmus, and is not affected by light, as is the case with the latter. Tho alkaline reaction is produced in natural or atmospheric waters; and the presence of nitrites, which change the red paper to purple, is indicated in greater dilution than with iodide starch.

4429. Ozonometer

4429.      Ozonometer. This name has been given to paper prepared with a mixed solution of starch and iodide of potassium. It is white, but is turned blue by ozonized air when exposed to it in a slightly moistened state. This test is sufficiently delicate to detect the presence of ozone in the atmosphere.