Dr. Pereira's Elements of materia medica and therapeutics : abridged and adapted for the use of medical and pharmaceutical practitioners and students and comprising all the medicines of the British Pharmacopœia, with such others as are frequently ordered in prescriptions or required by the physician / edited by Robert Bentley and Theophilus Redwood ; with an appendix.

  • Jonathan Pereira
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: Dr. Pereira's Elements of materia medica and therapeutics : abridged and adapted for the use of medical and pharmaceutical practitioners and students and comprising all the medicines of the British Pharmacopœia, with such others as are frequently ordered in prescriptions or required by the physician / edited by Robert Bentley and Theophilus Redwood ; with an appendix. Source: Wellcome Collection.

    49/1180 (page 17)
    The first distilled portion is to be rejected, as it may contain carbonic acid, ammonia, and other volatile impurities. The latter portions are not to be distilled, to guard against empyreuma from the charring of organic matters. The still in which the operation is conducted ought not to be employed for any other purpose, other- wise the water is apt to acquire a faint odour, and taste of the last matters subjected to distillation. [§ Tests.—A fluid ounce of it evaporated in a clean glass capsule leaves scarcely a visible residue. It is not affected by sulphuretted hydrogen, oxalate of ammonia, nitrate of silver, chloride of barium, or solution of lime.] If turbidness, milkiness, or precipitate, be occasioned by any of these, we may infer the existence of some impurity in the water. But water which has been repeatedly distilled gives traces of acid and alkali when examined by the agency of voltaic electricity, which, therefore, is the most delicate test of the purity of water! Distilled water also usually contains traces of organic matter. Nitrate of silver is the most delicate test of its presence. A solu- tion of this salt in pure water, preserved in a well-stoppered bottle, undergoes no change of colour by exposure to light; but if any vegetable or animal matter be present, the liquid acquires a dark or reddish tint. Properties.—Distilled water has the following properties : —at ordinary temperatures it is a transparent liquid, colourless, taste- less and inodorous, and miscible with alcohol in all proportions, with ether in certain proportions, not miscible with the fixed oils. Water rapidly absorbs some gases, as hydrochloric acid, ammonia,' - &c It is neither combustible nor a supporter of combustion A cubic inch at 62° Bar. 30 inches, weighs 252-458 grains, so that this fluid is about 815 times heavier than atmospheric air; but being the standard to which the gravities of solids and liquids are referred, its specific weight is usually said to be 1. An imperial gallon weighs, at 62°, 10 lbs. or 70,000 grs. Water has the greatest density at 39'2° F. At a temperature of 32° it crystallises, and in so doing expands. The sp. gr. of ice is 0-918. The fundamental form of crystallised water (ice) is the rhombohedron. Water evaporates at all temperatures, but when the barometer stands at 30 inches water boils at 212° and is converted into steam, whose bulk is about 1700 times that of water, and whose sp. gr. is 0-622 (that of atmospheric air being 1). In its chemical relations water may be regarded as a neutral body. It reacts neither as an acid nor as an alkaline or basic body. It combines with acids, alkalies, and many salts. If a saline com- pound absorbs water from the atmosphere, it is said to be deliques-