Calcii Phosphas

It is well to remember that fresh precipitates are more soluble in appropriate solvents than the same precipitates when dried. This fact was taken advantage of by a dispenser in compounding the following prescription:

Take one teaspoonful three times daily.

Six drachms of citric acid did not completely dissolve stock phosphate, but freshly precipitated phosphate dissolved in half an ounce of acid.

Chloral Hydras behaves towards alcohol like butyl-chloral hydrate, and is decomposed by alkalies with liberation of chloroform, as in the following mixture:

This is a bronchitis-mixture which in two days becomes quite strong in chloroform, and then seems to be more active. Substances with which chloral hydrate liquefies (see page 97) do not as a rule make good aqueous mixtures with it; thus:

In this monochloral-antipyrin is formed and is deposited as oily drops, resembling butyl-chloral alcoholate in behaviour. This is probably a case of salting-out, but if chloral hydrate 1, and phenazone 1, be separately dissolved each in water 6, and mixed, the solution is clear. Combination of the two seems to be promoted when they are dissolved together. Many cases of liquefaction and precipitation are due to the substitution of one molecule for another in a compound, and the more complex the molecule substituted the more insoluble is the product. Chloral hydrate is one of the agents that make antipyrin solutions green. See page 295.

Creosotum

The utility of creosote and its active principle, guaiacol, in the treatment of consumption has revived the prescribing of this old remedy. In doses of a minim or two creosote presents little difficulty in compounding in liquid form, as an ounce of water dissolves about 2 minims of it. Mistura creosoti, B.P., is a good example of such a mixture, the formula being:

Dissolve the creosote by shaking with 14 ounces of the water, add the spirit and the syrup, and make up with water.

Weak mixtures like this are given for gastric troubles, such as flatulence and hiccough. In the larger doses required in phthisis, 5 minims being frequently given, it is best administered in capsules, the creosote being mixed with its own volume of olive oil. Similar mixtures of oil and creosote are sometimes prescribed as emulsions with gum acacia to be compounded in the usual manner. Acacia mucilage alone suffices to suspend the creosote, as in the following instance:

The prescriber wished this to be dispensed with acacia mucilage, but a much better mixture is obtained by mixing the liquid extract and the same quantity of mucilage with 3 ounces of water in a bottle, and adding, all at once, a mixture of the (1) creosote, (2) S.V.R., and (3) tincture, shaking gently, and making up. It is frequently prescribed with cod-liver oil, but does not give a clear solution in this case.A mixture of equal volumes of creosote, absolute alcohol, and castor oil dissolves in cod-liver oil in any proportion. The cloudiness produced by mixing lime-water and spirit is cleared by creosote.