Mercurous Chloride

A dispenser who had a prescription for 1-grain calomel powders was so struck with the minuteness of the portion that he added 2 grains of sugar of milk to make bulk. This is not considered justifiable, but it is open to consideration whether fractions of a grain of dense substances should not be made up as is the case with pills, and were such prescriptions more frequent than they are, the question would have been discussed and settled before now. Homoeopathic powders are dispensed on this plan. A doctor prescribed the following with excellent results in infantile diarrhoea:

Fiat pulvis. Mitte xxiv. Sig. : One every hour.

There is nothing for it but to guess when dividing the powder, but it would be a boon to the dispenser and nurse alike if the bulk were made up to 24 or 30 grains before division. This is a case which recalls the old Scotchwoman's remark, 'Dinna be sae sparin'wi' it: it's for a mitherless bairn.'

Salts which may mutually decompose each other must be mixed in a perfectly dry condition, and should be stirred together lightly in the mortar. Instances are tartrate of potassium with sulphate of sodium, tartrate of potassium with chloride of ammonium, nitrate of potassium with salicylate of sodium. Effervescing lemonade-powder should be mixed by first rubbing together the tartaric acid with the sugar in a previously warmed mortar and then stirring in the bicarbonate of sodium very lightly. The powders should not be dried at a temperature above 300 C, or they are more liable to absorb moisture afterwards.

Squill and Ammoniacum in Powder keep perfectly in a bottle with an accurately fitting stopper, which should be wiped each time it is used, so that no particles are left between the stopper and neck. If the stoppering is not quite perfect, a little vaseline will make it airtight.

Powders for Lotions or other external purpose should be sent out in a different coloured paper from that used in other cases. A coloured paper is useful to distinguish at once between an internal and an external remedy. The powder should in all cases, however, be wrapped in waxed paper first, as the colouring of the paper may be altered by the powder. This would certainly be the case with the following :

Misce et divide in pulveres xij.

When mixed, deliquescence takes place, owing to the water of crystallisation and consequent interaction of the salts. Therefore the salts must be separately dried before mixing, and wrapped in waxed paper, when the powders keep well.