Manual of dispensing, 1938 / War Office.

Date:
1938
Catalogue details

Licence: Public Domain Mark

Credit: Manual of dispensing, 1938 / War Office. Source: Wellcome Collection.

    349/394 (page 337)
    (3) Lubrication. It is necessary to lubricate the granules in order that they may pass at a regular rate through the compressing machine, and to prevent them from adhering to the lower punch. French Chalk (Talc) or Boracic Acid, up to a limit of 5 per cent. may be used for external use tablets ; liquid paraffin in the form of a fine spray is employed in most cases for tablets intended for internal administration. (4) Compression. A simple compression apparatus consists of a hollow, cylindrical, metal tube or die, at the bottom of which is situated the concave lower punch. The granules are weighed out for each tablet, and each portion is introduced in turn into the cylinder, the upper punch is lowered into position, and compression effected by a sharp rap with a wooden mallet. Machines of various sizes and types, the larger of which are capable of turning out a thousand or more tablets a minute, have been invented. The granules are contained in a hopper from which they are fed automatically to the punches. The machines are capable of taking different sizes of punches and can be regulated to deliver the exact weight to the punches for compression. The punches are usually made of polished steel, but for certain substances which corrode steel, they may be of copper or agate. The degree of compression depends upon the nature of the tablet and the use for which it is intended. Tablets of potassium chlorate to be used as lozenges are compressed hard to give slow solubility, whereas those which are intended to dissolve in the stomach are only compressed sufficiently to withstand handling without breaking. Plasters (Emplastra) The operation of making a plaster usually means the spreading of one of the B.P. plasters upon a suitable material. Occasionally the ingredients of the plaster substance will be stated in the prescription, in which case this will need to be prepared before the plaster can be spread. The material upon which a plaster may be spread may be either white sheep-skin, calico, adhesive plaster, or even brown paper. Emplase. Belladonne’ .. -o in) X44 in. to be spread on leather The first step is to cut a piece of the material sufficiently large to leave a l-in. margin all round the spread surface—