paiit n.

Materia Medtca. — Guaiacum.

rally regarded as a gum resin, till Mr. Brande's experimentsshowed it to be a substance sui generis, differing from both gumand resin.

When guaiac is digested in water a little extractive only isdissolved, in the proportion of 9 parts in 100, and the infu-sion has a greenish brown colour and a sweetish taste. Alco-hol dissolves readily 95 parts in 100, and the solution is de-composed by the mineral acids, affording precipitates whichassume various tints of colour (see Tinctura Guaiaci). Sul-phuric ether- dissolves four parts in ten of guaiac, and whenevaporated on water leaves a tough, pellucid, pale brown pelli-cle, which appears to be pure guaiac: it becomes green aftersome time,- and a small portion of extractive remains dissolvedin the water. The alkaline solutions and their carbonates dis-solve it readily; and the solutions are precipitated by the dilu-ted sulphuric, the nitric, and the muriatic acids. Sulphuricacid dissolves it with scarcely any effervescence, affording asolution of a rich claret colour, which, when fresh prepared,deposits a lilac-coloured precipitate on the addition of water ;and when heated separates some charcoal. Nitric acid dis-solves it with a strong effervescence and a copious extricationof nitrous fumes ,• and when the solution is evaporated, ityields a large portion of oxalic acid : by the diluted acid it isconverted into a brown resinous substance. Muriatic acid dis-solves a small portion only, and affords a solution of a browncolour. I found that, during the solution of guaiac in theseacids, the heat which was evolved raised the thermometer inthe following proportions; in the sulphuric 44; in the nitric120; and in the muriatic 8 degrees. Nothing comes fromthe distillation of guaiac in water; but Mr. Brande obtainedfrom 100 parts of it, distilled per se in close vessels, the follow-ing products : acidulous water 5.5, thick brown oil 24.5, thinempyreumatic oil 30.0, charcoal remaining in the retort S0.5,and 9.5 of gases, which were chiefly carbonic acid and carbu-retted hydrogen. 1 From these experiments it is clear thatguaiac differs from resin; and we also learn that the mineralacids are incompatible in prescriptions with it.

It is sometimes adulterated with common resin and Manchi-nal gum. The former is detected by the turpentine emittedwhen the suspected guaiac is thrown on hot coals; and thelatter by adding to the alcoholic solution a few drops of sweetspirit of nitre, and diluting with water; the guaiac is precipi-tated, but the adulteration floats in white striae.

Medical properties and uses. -— Both the wood and the guaiacare stimulant, diaphoretic, diuretic, and purgative. The wood

1 Philosophical Trans. 1806; and Phil- Mag. xxv. 107,