Granulated effervescent salts are produced by heating mixtures of powdered citric acid, tartaric acid, sodium bicarbonate, and sugar to a certain temperature, until they assume the consistency of a paste, which is then granulated and dried.

If effervescent caffeine citrate, antipyrin, lithium citrate, etc., are to be prepared, the powder need not be dried before effecting the mixture, but if sodium phosphate, sodium sulphate, or magnesium sulphate are to be granulated, the water of crystallization must first be removed by drying, otherwise a hard, insoluble and absolutely non-granulable mass will be obtained. Sodium phosphate must lose 00 per cent of its weight in drying, sodium sulphate 56 per cent, and magnesium sulphate 23 per cent.

Naturally, water and carbonic acid escape on heating, and the loss will increase with the rise of temperature. For the production of the granulation mass it must not exceed 158° F., and for drying the grains a temperature of 122° F. is sufficient.

The fineness of the mesh should vary according to the necessary admixture of sugar and the size of the grains.

If the ingredients should have a tendency to cling to the warm bottom, an effort should be made immediately upon the commencement of the reaction to cause a new portion of the surface to come in contact with the hot walls.

When the mass is of the consistency of paste it is pressed through a wire sieve, paper or a fabric being placed underneath. Afterwards dry at sufficient heat. For wholesale manufacture, surfaces of large size are employed, which are heated by steam.

In the production of substances containing alkaloids, antipyrin, etc., care must be taken that they do not become colored. It is well, therefore, not to use heat, but to allow the mixture to stand in a moist condition for 12 hours, adding the medicinal substances afterwards and kneading the whole in a clay receptacle. After another 12 hours the mass will have become sufficiently paste-like, so that it can be granulated as above.

According to another much employed method, the mass is crushed with alcohol, then rubbed through a sieve, and dried rapidly. This process is somewhat dearer, owing to the great loss of alcohol, but presents the advantage of furnishing a better product than any other recipe.

Effervescent magnesium citrate cannot be very well made; for this reason the sulphate was used in lieu of the citrate. A part of the customary admixture of sulphate is replaced by sugar and aromatized with lemon or similar substances.

An excellent granulation mass is obtained from the following mixture by addition of alcohol:

Parts by weight

Sodium bicarbonate...... 30

Tartaric acid............ 15

Citric acid.............. 13

Sugar.................. 30

The total loss of this mass through granulation amounts to from 10 to 15 per cent.

To this mass, medicinal substances, such as antipyrin, caffeine citrate, lithium citrate, lithium salicylate, phenacetin, piperacin, ferric carbonate, and pepsin may be added, as desired.

In order to produce a quinine preparation, use tincture of quinine instead of alcohol for moistening; the quinine tincture is prepared with alcohol of 96 per cent.