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.

    1110/1180 (page 1078)
    [§ AMMONLZE NITRAS. Nitrate of Ammonia. NH3,M)5,HO or NH4N03. Produced by neutralising diluted nitric acid with solution of ammonia or carbonate of ammonia, evaporating the solution until crystals are obtained, and keeping these fused at a temperature not exceeding 320° until the vapour of water is no longer emitted. Characters and Tests.—A white deliquescent salt, in confused crystalline masses, having a bitter acrid taste. Soluble in less than its own weight of water, and sparingly soluble in rectified spirit. A solution of one part in eight parts of distilled water gives no precipitate with solution of nitrate of silver or of chloride of barium. Heated with caustic potash, it evolves ammonia ; with sulphuric acid it emits nitric acid vapour. It fuses at a temperature of 320°, and at 350° to 450° it is entirely resolved into nitrous oxide gas, NO or N20, and the vapour of water.] This salt is used in the production of nitrous oxide gas, which is extensively administered by dentists as an anaesthetic. It is impor- tant that the salt when used for this purpose should be free from impurity, as indicated by the tests given in the Pharmacopoeia. The action of heat on nitrate of ammonia was studied by Sir Humphrey Davy, who ascertained that compact or anhydrous nitrate of ammonia undergoes little or no change at temperatures below 260°; that at temperatures between 275° and 300° it slowly sublimes without decomposition and without becoming fluid ; that at 320° it becomes fluid and still slowly sublimes; that it never assumes or continues in the fluid state without decomposition, but at tempera- tures between 340° and 480° it decomposes rapidly. These state- ments relate to the anhydrous salt such as the Pharmacopoeia orders. The prismatic and fibrous nitrates of ammonia (see p. 36), become fluid below 300°, and undergo ebullition between 360° and 400°, merely giving off water without decomposition. They may be heated to 430° without either decomposing or subliming, but at 450° they decompose without previously losing their water of crystallisation. The temperature ought not to be allowed to rise above 480° in preparing the nitrous oxide for the purpose of inhalation. At a much higher temperature the product may be contaminated with nitric oxide, the presence of even a small quantity of which would be very injurious. (See also p. 20.)