Olea Essentialia

The remarks in regard to the preparation of aromatic waters (page 52) must be considered in connection with aqueous mixtures containing excess of essential oils. It has been shown that the solubility of oils in water rarely exceeds 1 minim per ounce, and that the rapidity of solution is increased by dividing the oils into small particles, as by triturating with magnesium carbonate or any other powder, or by dissolving in spirit and pouring the solution into water, when the oil dissolved is precipitated in small particles. This latter example shows the condition which the dispenser should aim to get any essential oil into when it is in excess in mixture, and to keep it in that condition by a suitable emulsifying agent, such as acacia. On the next page are examples which do not come within this rule.

What is ess. limonis? There is no official preparation of that name, but oil of lemon is commercially known as essence of lemon. It will not, however, make a nice mixture in the case of No. I., but a soluble essence of lemon (or its equivalent, a 1-in-1 tincture of fresh lemon-peel) produces a mixture of good flavour, which goes well with cod-liver oil. Note the chemical incompatibility of the first two ingredients; fortunately the limited reaction and the presence of glycerin (which should be mixed with the Fowler's solution) prevent a precipitate of calcium carbonate. No. II. was dispensed clear by using spirit and a minim of chloroform instead of aq. chloroformi.

Phenazonum

This is the B.P. name for antipyrin or phenyldimethylisopyrazolone, C6H5(CH3)2C3HN20. In some respects phenazone may be regarded as an artificial alkaloid, but its characters are sui generis:(i) it is alkaloid-like in being an aniline derivative;(2) it is unlike alkaloids in its great solubility (it is a free 'base'); (3) like them it gives heavy precipitates with alkaloidal reagents; and (4) it differs from most medicines in being a potential synthetic dye - that is, although a colourless substance, it is on the verge of colour-production, and certain reagents (occasionally prescribed with it) produce the colour. Again, we have in phenazone an excellent example of the importance of chemical knowledge to the dispenser. The characters of the substance may be classified thus:

It is precipitated As insoluble tannate by tannic acids, therefore is incompatible with galenical preparations containing tannin.

As insoluble salicylate in certain mixtures of phenazone and alkaline salicylates. As hypnal by chloral hydrate (see page 286). Similar precipitates are given with phenol solutions and with beta-naphthol.

As iodo-antipyrin with free iodine in excess.

As a mercury compound (white) with mercuric chloride in certain proportions.

It is colouredGreen with nitric and nitrous acids, owing to the formation of iso-nitroso-antipyrin, and similarly with spirit of nitrous ether or other alkyl nitrites in presence of water and oxygen (see below).

Red with ferric chloride, and...

Yellow on the addition of sulphuric acid to the ferric-chloride mixture, the same effect being produced by alum alone, no doubt owing to the minute traces of iron in commercial alum and the ionisation 'of the sulphuric radicle in it.

The following prescriptions from every-day practice illustrate a few of these reactions. Although antipyrin salicylate (salipyrin) is but feebly soluble in water (1 in 200), fairly strong solutions of antipyrin and sodium salicylate in distilled water may be mixed together without precipitation of antipyrin salicylate- indeed, water seems to split up the salipyrin, precipitating a small amount of salicylic acid, as in the following case:

1 Ionisation is the condition in which chemicals are supposed to exist in solution, with their constituent radicles in the free state not as molecules, but as atoms electrically charged with positive or negative electricity, according to the nature of the radicle, and, therefore, in a condition which renders the radicles extremely susceptible to unite with or neutralise other radicles which may be brought into the field of their action, especially if the new radicles are a truer complement to them.

The two solids of No. I. dissolved separately (each in half the water) gave clear solutions, but on mixing a fine crystalline precipitate appeared in a few minutes. This does not happen with plain distilled water, but if it be feebly acidified with acetic acid, the same crystalline precipitate appears, although the amount of acid is insufficient to precipitate salicylic acid from the sodium salicylate. Observations by Millard and Stark show that the oily mixture of antipyrin and sodium salicylate is slightly alkaline, but when water is added, the reaction becomes acid.

A correspondent of The Chemist and Druggist observed that if he dissolved the antipyrin of No. II. in the chloroform-water and added it to the other ingredients previously mixed, no green colour developed. This is no doubt owing to the fact, noted on page 73, that ammonium acetate and ethyl nitrite interact, so that there is free acetic acid in the mixture instead of free nitrous acid, consequently no green colour is produced. Professor Chas. Caspari, jun., having questioned the statement that the mixture does not become green, and, if so, that the fact is due to the ammonium-acetate solution being alkaline, Mr. T. Dunlop experimented and proved the correctness of the first observer's statement (C. & D., 1898, 1. 357, 497)- It is advisable in any case to add a little potassium bicarbonate to mixtures containing antipyrin and spirit of nitrous ether so that the green colour will not be produced. The observations of Evans (C. &D., 1889,1. 402) proved that iso-nitroso-antipyrin is not poisonous, but Wood and Marshall (same volume) found that in acid solution iso-nitroso-antipyrin gives off on standing a small quantity of hydrocyanic acid- too little, however, to be alarmed about.

Amyl nitrite in aqueous solution also gives the green colour, because it, also, liberates nitrous acid.

A becomes green, and b (an Australian cough-mixture) changes to a beautiful golden-yellow colour.