Elements of pharmacy, materia medica, and therapeutics. / By William Whitla.

  • Whitla, William, 1851-1933.
Date:
1882
Catalogue details

Licence: Public Domain Mark

Credit: Elements of pharmacy, materia medica, and therapeutics. / By William Whitla. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    weight, the scales that are being constantly used to weigh as much as two or three drams should not be employed. For this purpose the small beam and scales figured should be used, and the substance gradually added, particle after particle, from a small spatula till the scale comes to the level of the opposite, and remains there. In this manner the -^^-^ of a grain can be easily appreciated. Fig. 1. It is very often necessary to weigh small quantities of soft extracts for pills. This should only be done in this way :— Two little pieces of smooth writing paper should be made of the same size, which is accurately done by cutting a piece out of two leaves, one placed in contact with the other. When two pieces of precisely the same size and weight are thus ob- tained, one should be placed on the left hand scale along with the weights ; the other is to receive upon it the soft substance, and to be placed in the opposite scale, and when the requisite weight of material is added it can easily be detached from the paper with a knife. The same plan should be used with cor- rosive substances, like iodine, if the scale is not of glass. The student should have clear ideas about weights ; the Pharmacopoeia orders all solids to be weighed, and all fluids, except mercury and treacle, to be measured. It recognises no weight between a grain and an ounce, the ounce being equal to 4375 grains, and the pound being equal to 16 ounces, or