Preparation Of The Material

Chemical salts which are to be compressed should be in the granular form as supplied for the purpose by chemical-manufacturers. All powders must be granular. On the dispensing scale a considerable amount of 'faking' is necessary in making tablets of pure substances. Thus, an excipient must be added to make the powders adhere, and the dry powder must be sprayed with an ethereal solution of liquid paraffin (3ss. to .) or vaseline (gr. x. to ) immediately before compression. The latter treatment prevents the formation of a clear solution of the tablets in distilled water. The following formulae by Edel show the requisite treatment:

For Doses of a Few Grains.

Example.

Reduce the phenacetin to fine powder, and mix. Moisten with a few drops of syrup and a sufficiency of water. Pass through a No. 20 sieve, dry, and again sift. Spray the powder with 20 to 30 drops of vaseline solution, and make 100 tablets.

In the same manner the following are made:

Acetanilide, antipyrin, bismuth salts, chloralamide, salicin, salol, and sulphonal.

Small Tablets of Fractional Grain Doses.

Example.

Mix thoroughly, add 4 or 5 drops of simple syrup, then moisten with water, and pass through a No. 20 sieve. Dry. Lubricate the granular powder by spraying 10 drops of vaseline solution over it, and make into 100 tablets.

In the same manner may be made tablets of the undermentioned remedies, adjusting the weight of sugar of milk taken to the dose of the medicine. Thus, if aloin tablets gr. j. are to be made, only 50 gr. of sugar of milk is required for the 100 tablets:

Aloin, arsenious acid, caffeine, codeine, digitalin, extract of nux vomica, mercurous chloride, mercurous iodide, morphine hydrochloride, podophyllin, and strychnine.

These are simple forms. Many substances require no addition, this being especially true of the granular salts ; but even in these cases the addition of 2 to 5 grains of finely powdered French chalk to the powder for 100 tablets is an advantage, the mixture being well sifted. Disintegrating tablets are obtained by adding 2 to 4 grains of powdered arrowroot to each ounce of material. On the other hand, tablets required to dissolve slowly should have 5 per cent, of powdered acacia mixed with the powdered substance before damping and granulating.

Hypodermic tablets are made with a basis of granulated sodium sulphate or sodium chloride. Sodium acetate is used for diluting morphine acetate. The powder for each tablet should be weighed.

Tincture tablets are made by mixing with powdered sugar of milk (1 ounce of tincture to 1 ounce of the sugar). Warm carefully on a water-bath until the mixture is sufficiently dry to granulate through a sieve. Dry in a warm-air cupboard, and compress into tablets of the required size, reckoning each grain of the powder as equal to a minim of tincture.

A mixture of cocoa powder and sugar of milk was suggested by Mr. Stewart Hardwick as a tablet-vehicle, the general formula for one tablet being:

This is compressed in the ordinary way. White and Robinson (B.P.C., 1902) improved upon this by suggesting a mixture of oil of theobroma 1 part, and starch 3 parts, the oil being melted and the starch-powder stirred in before cooling. Of this mixture 1 to 2 parts is added to each 5 parts of the powder to be compressed, mixed well but lightly in a mortar, divided into doses, and each dose compressed. For working on the large scale White and Rodwell (B.P.C., 1903) found certain disadvantages in the 1902 excipient, and devised the following:

Method I. Theobroma Emulsion.

Dissolve the soap in 25 parts of water by heat, add the hot solution to the melted theobroma, and mix by whisking or agitation; shake in the tragacanth, add the benzoic acid, then the remainder of the water.

Method II. Ether-alcohol Solution of Theobroma.

Dissolve and add an equal volume of rectified spirit as required for use.

The following formulae illustrate the use of each solution: