This is the most important of all the menstrua employed by the homoeopathic chemist, and too great care cannot be exercised to insure its purity. It should be purchased in the form of Rectified Spirit of first quality, 60° O.P., from a respectable distiller, and should then be mixed with purified animal charcoal, using a bulk of charcoal equal to about one-tenth of the bulk of spirit, and re-distilled in a glass apparatus (a tubulated glass-stoppered retort with a long beak placed in a capacious sand-bath and heated by gas answers well),* with all the precautions mentioned under "Water," and no alcohol which has not undergone this fresh distillation should be employed in making any attenuations intended to be carried beyond 3x

* Any glass or porcelain retort used for the purpose must first be purified by boiling distilled water in it rapidly until the product ceases to give a precipitate with Nitrate of Silver.

Characters and Tests. - Colourless, transparent, very mobile and inflammable, of a peculiar pleasant odour, and a strong spirituous burning taste. Burns with a blue flame, without smoke. Specific gravity 0.8298. Remains clear when diluted with distilled water. Odour and taste purely alcoholic. 4 fluid ounces with 30 grain measures of the volumetric solution of Nitrate of Silver exposed for twenty-four hours to bright light, and then decanted from the black powder which has formed, undergo no further change when again exposed to light with more of the test.

The following strengths should always be kept on hand, and should be made by the chemist himself, using distilled water for the dilution, prepared as already described.

1. Dilute Alcohol. - This is made by mixing equal measures of rectified spirit and distilled water. The mixture should have a density of 0.940, and contains about 39 per cent. by weight of absolute alcohol.

2. Proof Spirit (of the British Pharmacopoeia). - This is made by mixing 5 measures of rectified spirit with 3.2 measures of distilled water. The mixture should then be agitated and allowed to cool to 60° P., and a sufficient quantity of distilled water added to increase the bulk to 8 measures. It should have a density of 0.920, and contains 49 per cent, by weight of absolute alcohol.

* In distilling alcohol great care should he taken to prevent explosion. The stopper of the retort must be kept loose, in order that it may act as a safety valve.

3. Spirit of 20 O.P. (over proof). - This is made by mixing 6 measures of rectified spirit with 2 measures of distilled water, the contraction resulting from the mixture of the two liquids being made good in the manner directed under "Proof Spirit." It should have a density of 0.8939, and contains 61 per cent, by weight of absolute alcohol.

4. Spirit of 40 O.P. (over proof). - This is made by mixing 7 measures of rectified spirit with 1 measure of distilled water, the contraction being made good as directed under "Proof Spirit." It should have a density of 0.8646, and contains 73 per cent, by weight of absolute alcohol.

5. Rectified Spirit (= 60 over proof) has, as before stated, a density of 0.8298, and contains 87 per cent, by weight of absolute alcohol.

6. Absolute Alcohol, having a density of about 0.795, is required for a few of the preparations, and may be obtained from rectified spirit in the following manner:-

Take of

Put the carbonate of potash and spirit into a stoppered bottle, and allow them to remain in contact for two days, frequently shaking the bottle. Expose the slaked lime to a red heat in a covered crucible for half an hour, then remove it from the fire, and, when it has cooled, immediately put the lime into a flask or retort and add to it the spirit from which the denser aqueous solution of carbonate of potash, which will have formed a distinct stratum at the bottom of the bottle, has been carefully and completely separated. Attach a condenser to the apparatus, and allow it to remain without any external application of heat for twenty-four hours; then, applying a gentle heat, let the spirit distil until that which has passed over shall measure 1 1/2 fluid ounce; reject this, and continue the distillation into a fresh receiver until nothing more passes at a temperature of 200°.

To obtain greater purity, this may be re-distilled with charcoal in the manner described on pp. 2 and 3.

Characters and Tests. - Colourless and free from empyreu-matic odour. Specific gravity 0.795. It is entirely volatile by heat, is not rendered turbid when mixed with water, and does not cause anhydrous Sulphate of Copper to assume a blue colour when left in contact with it.

It is very necessary to preserve absolute alcohol in well-stoppered and capped ether bottles, since it attracts water from the air as greedily as Sulphuric Acid, and would therefore be rapidly spoilt by exposure.