This section is from the book "British Homoeopathic Pharmacopoeia", by The British Homoeopathic Society. Also available from Amazon: British Homoeopathic Pharmacopoeia.
Systematic dilution of medicines according to a fixed scale constitutes another of the peculiarities of homoeopathic pharmacy. When Hahnemann had convinced himself of the curative power of infinitesimal doses he devised and carried out the plan of making a series of preparations of each medicine, every one of which should contain exactly 100 times less of the drug than the one before it, and this constitutes the centesimal scale. His followers, however, being desirous of having preparations of a strength midway between those recommended by Hahnemann, adopted the plan of diluting in the proportion of 1 in 10 in place of 1 in 100, thus constituting the decimal scale. In consequence of this very great confusion has arisen; and it is most essential that one or other should be adopted exclusively. After a careful review of all the arguments in favour of both scales, it has been determined to adopt the centesimal scale for prescribing, while the decimal possesses so many advantages in the preparation of the drugs that it should be always followed in the making of the triturations and other attenuations. When referring to the subject of designating the attenuations, an easy method will be described by which to avoid the possibility of any confusion arising from the use of one scale for preparing and the other for prescribing. The method of making the attenuations is as follows: -
Take a perfectly clean new bottle (say a half-ounce phial), fit a good new cork into it, and then, having removed the cork, pour in 20 minims of the mother tincture, then add 180 minims of spirit of the same alcoholic strength as that with which the mother tincture was prepared, cork the bottle, and, grasping it in the right hand, with the thumb held firmly over the cork, shake it well, letting each shake terminate in a jerk by striking the closed right hand against the open palm of the left hand; having given several such shakes, the attenuation is finished, and should be marked lx or A: 20 minims of lx, mixed and well shaken with 180 minims of spirit, will then form 2x or 1; and 20 minims of 1 with 180 minims of spirit, well shaken, will form 3x or B; and so on up to the highest attenuation required.*
The strength of the spirit used for the attenuations must be carefully attended to according to the following rules: -
I. - The first attenuation made from a trituration (which will be 4) must be made as follows: Dissolve 1 grain of the 3rd centesimal trituration in 50 minims of distilled water, and then add gradually 50 minims of rectified spirit, thus forming dilute alcohol.
N.B. - As sugar of milk is not soluble in less than six times its weight of cold water, and is insoluble in alcohol, a decimal solution of a trituration could only be made with pure water, and would not keep; the centesimal scale, therefore, must be followed in preparing the first solution of a trituration.
a. The next attenuation, viz., 9x, must be made with proof spirit.
b. The next, viz., 5, and all higher attenuations, must be made with rectified spirit, i.e., 60 O.P.
* It is recommended to keep all the attenuations in glass-stoppered bottles.
II. - The first attenuation of any mother tincture (which will always be 1x or A) must be made with spirit of the same strength as that used in making the mother tincture: hence a. When the mother tincture is made with proof spirit, attenuation lx or A must be made also with proof spirit, attenuation 1 with spirit 20 O.P., attenuation 3X or B, and all above that, with rectified spirit.
b. When the mother tincture is made with dilute alcohol, attenuation lx or A must be made with dilute alcohol, 1 with proof spirit, 3X or B with spirit 20 O.P., and all above that with rectified spirit.
c. When the mother tincture is made with spirit 20 or 40 O.P., attenuation lx or A must be made with a corresponding strength of spirit, 1 and all above that with rectified spirit.
d. When the mother tincture is made with rectified spirit, the same will be used for all the attenuations.
III. - The attenuations made from watery solutions require to be modified by so many causes, such as the solubility of the medicine in alcohol, the tendency or otherwise to any chemical action between the alcohol and the substance to be attenuated, that the rule is in these cases laid down separately for each particular substance.