Active Ingredients. - The best Siam benzoin occurs in white or reddish tears, agglutinated together by a darker colored and amorphous portion, the fracture presenting an amygdaloid appearance. The odor is agreeable, to some persons it is fragrant; the taste is balsamic and slightly sweet. When heated, it melts, and gives off benzoic acid in the form of white fumes, with a little empyreumatic oil, and then gradually consumes away. It is soluble in alcohol, and in solution of potash. Ether dissolves the resinous element in part. Sp. gr., 1.092.

The principal constituents are about 80 per cent. of resin, and 10 to 20 per cent. of benzoic acid, HO C14H6O3, or perhaps HC7H5O2. This acid was known as long ago as 1608, and is procurable by sublimation. It presents itself in the shape of soft white feathery and flexible crystals, with a pearly lustre, and usually with a slight impregnation of the above-mentioned empyreumatic oil, which confers on it the odor of the original mass. It is soluble in alcohol, also in solutions of lime and of caustic alkalies, from which it is precipitated by hydrochloric acid; but in water it is very sparingly soluble, requiring about 25 parts of boiling, and about 200 parts of cold, for complete solution. It melts at 248°, and boils at 462°, entirely subliming when pure. Of the resin, one portion is soluble in ether and in carbonate of potash, and the other portion is not soluble.

Physiological Action. - If chewed for any length of time, benzoin causes irritation of the fauces: the fumes produced by heat and combustion are also irritating; and the powder, if inhaled, excites sneezing. Of the action of this substance upon the body, when swallowed, we possess, however, no exact knowledge. Taken in large doses, it is said to quicken the circulation, and to increase the flow of urine and the cutaneous exhalations. Schreiber swallowed half an ounce of benzoic acid, divided into 40 doses, in the course of two days, with the result of prolonged irritation of the throat, and a sense of warmth, first in the abdomen, and afterwards throughout the body; the pulse at the same time became more frequent, though afterwards it subsided gradually. After the first day, the perspiration and the expectoration were augmented, but the quantity of urine was unchanged. The head was somewhat confused, and digestion was temporarily impaired.

Professor Woehler, in 1831, expressed his opinion that benzoic acid, during digestion, was probably converted into hippuric acid; and Dr. Ure states that the administration of benzoic acid causes uric acid to disappear from the urine, the latter being replaced by hippuric acid. On this ground he recommends it as a remedy for the gouty and calculous concretions of uric acid. Keller, on the other hand, maintains that the uric acid undergoes no change, and that the benzoic is directly converted into hippuric acid. Garrod likewise takes this view, and states also that it renders the urine more acid as well as somewhat irritating. That benzoin is a local irritant there is no doubt. The vapor, when too concentrated, induces violent coughing and sneezing.

Therapeutic Action. - Being stimulant and expectorant, benzoin is usefully employed in bronchitis and other chest affections. By reason, however, of its irritant effects upon the mucous membrane, great care must be taken not to administer too large a quantity, such as would over-stimulate that membrane. In the chronic bronchitis of old persons it proves especially useful. Benzoin has likewise been employed with advantage in chlorosis and other uterine disorders.

The compound tincture is an admirable local application for sore nipples, and for chapped lips and hands. When intended to be thus employed, one part of this tincture should be added to four parts of glycerine. Mixed with water, it is used as a cosmetic to remove freckles and other eruptions. The special cosmetic called "Virgin's milk" is a spirituous solution in about twenty parts of rose-water. "Friar's Balsam,"

"Wade's Drops," and "Jesuits' Drops" are nothing more than forms of the compound tincture.

Benzoic acid is used in chronic cystitis, and as a stimulant of the mucous membrane of the bladder. It often removes the foetor of the urine in cases of irritable bladder induced by enlarged prostate. It is likewise a very useful remedy in cases of phosphatic urine dependent upon irritation of the bladder, being perfectly capable of rendering the urine acid in a short time. Hence, too, it renders alkaline urine acid.

Benzoate of ammonia acts in a manner very similar to benzoic acid, and is thus a very convenient salt for exhibition in cases such as are amenable to the pure acid.

Benzoin, it may be added, is the basis of "Turlington Balsam," a useful preparation for the healing of wounds and ulcers, and especially valuable to travellers and others who cannot easily obtain surgical aid. It is employed likewise in the preparation of "paregoric elixir," and in the manufacture of court-plaster and of pastiles.

Preparations and Dose. - Tinct. Benzoini, 3 ss. - j. (2. - 4.);

Tinct. Benzoini Comp., 3 ss. - j. (2. - 4.); Acidum Benzoicum, gr. v. - xv. (.30 - 1.); Ammonii Benzoas, gr. v. - xv. (.30 - 1.); Ungt. Benzoini.