"ACIDUM ACETICUM.-Take of Acetate of lead any convenient quantity: heat it gradually in a porcelain basin by means of a bath of oil or fusible metal (8 tin, 4 lead, 3 bismuth) to 320° F.; and stir till the fused mass concretes again: pulverize this when cold, and heat the powder again to 320°, with frequent stirring, till the particles cease to accrete. Add six ounces of the powder to nine fluidrachms and a half of Pure sulphuric acid contained in a glass mattrass: attach a proper tube and refrigeratory; and distil from a fusible-metal-bath with a heat of 320° to complete dryness. Agitate the distilled liquid with a grain or two of red oxide of lead to remove a little sulphurous acid, allow the vessel to rest a few minutes, pour off the clear liquor, and redistil it. The density should be not above 1065."

In the Medical Gazette, I made several remarks on the more glaring imperfections of this process, and offered what I believed to be the only possible excuse for its introduction, namely, that it had never been tried. It now appears that this apology is no longer admissible, for from what Dr. Christison states, the process appears actually to have been attempted, and my wonder is therefore doubled that it should be retained.

After trying to perform the process described, but with very imperfect success, I stated numerous objections to it: first, Acetate of lead may be rendered anhydrous by exposure to a heat of 212°, with occasional stirring, instead of requiring, as directed, continual stirring, a temperature of 320°, obtained by the inconvenient and expensive method of a fusible metal-bath, or the disagreeable and dangerous one of an oil-bath. Secondly, The employment of a thermometer required when either a metal or oil-bath is used, is extremely troublesome, and it is very difficult, even with constant watching, to keep the fusible metal at the temperature directed, for it is very apt to rise above it; and, at a very few degrees below it, the mixed metals become solid. Thirdly, On account of the tenacity of the mixture of the sulphuric acid and acetate of lead, there is great difficulty in effecting a perfect admixture of them. Fourthly, The residual sulphate of lead, on account of its insolubility, is with difficulty removed from the matrass. Fifthly, Acetate of lead is more costly than acetate of soda, in the proportion of fourteen to ten. Sixthly, The last mentioned salt leaves a residue of sulphate of soda, easily washed out of the matrass. Seventhly, In expelling the water from the acetate of lead, the College give the operator the choice of two bad methods of effecting it, while in distilling the acid, they restrict him to the use of the worse. Eighthly, I showed that "a grain or two" of red oxide of lead could remove only of a grain of sulphurous acid, or from about 1-4000th to 1-2000th of the weight of the product of acetic

acid. Ninthly, In page 2 of the Pharmacopoeia, it is stated, that the density of the acid is "not above 1068.5," while at page 44 it is directed that the density should "be not above 1065."

In the second edition this process is retained, accompanied with all its principal bad qualities; some of the details are however corrected to a certain extent, not indeed, as in other instances, in accordance with the remarks which I offered, but in avoidance of the more tangible errors of the original; for example, for “a grain or two of red oxide of lead," we find now " a few grains;" and at page 2, the acetic acid is directed to have "a density not above 1068.5," as on the former occasion; whereas at page 48, it is stated that "the density is commonly from 1063 to 1065, but must not exceed 1068.5."

Dr. Christison (p. 7) after stating the composition, and giving the symbols of acetic acid, observes, that the "hydrated acid (A+Aq.) contains of course an additional equivalent of hydrogen and oxygen. The density of this when accurately prepared is 1063; but it often reaches 1065, owing to the presence of a little additional water. When of the former density one hundred minims (97 grains) neutralize nearly 242 grains of crystallized carbonate of soda." It follows therefore, that 100 grains of this acid neutralize 249 grains of carbonate of soda-eightynine grains of real acid, adopting the same equivalents for acetic acid and the carbonate as Dr. Christison does. This acid consequently consists of 11 water and 89 real acid, which are nearly in the proportion of 9, one equivalent of water to 73 of real acid, instead of 9 to 51.48 the strongest known, and mentioned by Dr. Christison as such; the error consequently amounts to above twenty-one parts of real acid.

Nor is this all in the above quotation we are informed, that acetic acid, when accurately prepared, has a density of 1063; "but it often reaches 1065;" now nothing is here said of acid of sp. gr. 1068.5, which, according to the Pharmacopoeia, the product may not improperly possess. Let us, then, compare the strengths of the acids of the various densities which the College must suppose to be nearly similar, with the statement of that of 1063, according to Dr. Christison, and of the stronger of 1068.5, according to the table which he has quoted; the first, I have just shown, must contain eighty-nine per cent., while, for the second, the table gives eighty-two. This difference, amounting to seven per cent., surely cannot be owing, as described by Dr. Christison, " to the presence of a little additional water."

This mis-statement of the saturating power of acid of 1063, is repeated so distinctly, that there is no occasion merely to infer it. Dr. Christison says, "between 1063 and 1077.7 the same density may indicate an acid of two very different degrees of

strength, the weaker of which is in fact, at 1063, less than half as strong as the stronger; while that of 1077.7 is intermediate, -the neutralizing power of 100 grains of these three acids being about 118, 186, and 250, as determined by the carbonate of soda." Adopting, as before, the same equivalent numbers as Dr. Christison, the acid saturating 250 must contain 89.73 per cent. of real acid, and consequently consist of one equivalent of acid and about two-thirds of an equivalent of water-a compound which I need hardly say, has never been formed.

Dr. Christison characterizes the tests of the London College for ascertaining the purity of acetic acid, as "unnecessarily minute." He does not seem to be aware that nitric and hydrochloric acid are occasionally used to adulterate this acid, but I have found both of them. Indeed, he says, that muriatic acid "does not occur as an adulteration."

There are many observations of Dr. Christison respecting acetic acid, which require correction: for example, he states, with respect to what he, in defiance of all modern and just chemical views, calls pyroligneous acid, that "it varies much in density, and therefore in strength," it ought of course to follow, that agreement in density should indicate similarity in strength; but it will appear from the table which Dr. Christison has inserted, that acid of 1068 may contain either 97 or 37 per cent. of hydrated acetic acid.

What

Dr. Christison observes (p. 5), that "the London College does not admit the pure acetic acid; while, with a disregard of correct nomenclature, which suits ill with its professions of accuracy in this respect, the name has been given to a weak acid about the density of 1050, containing not much above a third of its weight of the pure acid of the Edinburgh Pharmacopoeia." ever may have been the professions of accuracy of the London College it appears to me that they have at least endeavoured, as fully as the subject would admit of, to employ a consistent nomenclature; at any rate they have not adopted the avowed "patchwork" of the Edinburgh College.

Some critics are extremely difficult to please: because acetic acid contains more water than is absolutely requisite, we may infer that, according to Dr. Christison, it should have been called impure acetic acid; on the other hand, when potash containing only the proper quantity of water is called hydrate of potash by the London College, then it is "the newest and most refined" name for that substance, although it has been so called for more than a quarter of a century.

There are other statements contained in Dr. Christison's observations respecting acetic acid, which require correction, but having extended my observations on this subject to a great

length, I shall close them with briefly noticing his opinions with respect to rendering acetate of lead and acetate of soda anhydrous, and on one other subject.

"Of acetate of lead," Dr. Christison says, that "the chief difficulty lies in depriving the salt entirely of its water of crystallization. Spontaneous evaporation is too tedious a method of attaining this end; and the process is not sufficiently accelerated either in a confined space of air kept dry with sulphuric acid, or even by substituting a vapour-bath heat. But in a vacuum, with sulphuric acid to absorb the moisture, the crystallized acetate parts with the whole of its water in thirty-six hours; and this method is obviously applicable on the large scale."

In the Medical Gazette I stated, and I repeat the assertion, that acetate of lead is with great facility rendered anhydrous by exposure to the heat of steam. Dr. Christison, indeed, informs us that acetate of soda "is not so easily reducible as the acetate of lead to the anhydrous state without the escape of acid or charring of the residual salt." Again I repeat, what I before asserted, that this salt may be rendered anhydrous, and without either the loss of acid or charring, by exposure to a temperature of 212°. I venture also to state, that the method by sulphuric acid is obviously inapplicable on the large scale; and that what is described as "the more convenient method" of using a bath of oil or fusible metal is as inconvenient as possible.

It is, indeed, true that an equivalent of acetate of soda, as it contains more water than an equivalent of acetate of lead, requires longer exposure to heat to render it anhydrous; I found, for example, that 2740 grains of the soda salt, representing twenty equivalents, become anhydrous by exposure to 2120 during seventeen hours, while 3800 grains of the salt of lead, also representing twenty equivalents, required only twelve hours to produce the same effect.

Dr. Christison (Dispensatory, p. 6) referring to the method of the London College for obtaining acetic acid, says "the process for the weaker London acetic acid will be noticed under the head of pyroligneous acid, of which it is really a variety. The salt used in that process, the acetate of soda, is preferable to all other acetates in point of cheapness."

I am quite at a loss to conjecture what is meant by terming the acetic acid of the London Pharmacopoeia a "variety" of pyroligneous acid; indeed in p. 9 it is stated to be "nothing else than pyroligneous acid," because it is produced from the acetate of soda, which is prepared from wood by destructive distillation." If this be the case, what then is the "pure acetic acid of the Edinburgh Pharmacopoeia," which is produced from the acetate of lead, prepared by express direction from pyroligneous acid," obtained from wood by destructive distillation? (Edin. Pharm. p. 111.)

PLANTS WHICH MAY BE GATHERED, OR THEIR ROOTS DUG UP IN THE MONTH OF MAY.

COMMON SCurvy-grass, Cochlearia officinalis; Wood-sorrel, Oxalis acetosella; Lesser spearwort, Ranunculus flammula; the Odorous violet, Viola odorata; Rosemary tops, Rosmarinus officinalis; roots of Taraxacum, Taraxacum dens leonis; roots of Mallow, Malva sylvestris; roots of Bistort, Polygonum bistorta.

RHAMNUS FRANGULA (LIN).
"Black Alder."

TO THE EDITOR OF THE PHARMACEUTICAL JOURNAL.

DEAR SIR, I have frequently had opportunities of witnessing the good effects of the black alder, of which I send you a specimen, with a formula for the decoction.

It is purgative, alterative, &c., useful in secondary syphilis, chronic rheumatism, and cutaneous disorders.

Decoction-One ounce of the bark gently boiled in a pint and a half of water, till reduced to a pint. A wine-glassful to be taken twice or thrice daily.

Plymouth, April 7th, 1843.

Yours truly,

GEORGE MENNIE.

SICKNESS OCCASIONED BY EATING THE ROOT OF FRENCH BEANS.

TO THE EDITOR OF THE PHARMACEUTICAL JOURNAL.

1, Brettin Terrace, Chelsea, April 18, 1843. DEAR SIR, A customer of mine last Christmas was digging up some roots of the French Beans or Scarlet runners, and observing them to be very large and look very white when broken, thought he would taste them, thinking there could be no harm in partaking of the root of a vegetable which had formerly supplied his table. His family and maid-servant being also in the garden all partook of some-pronouncing them good and pleasant to the taste; presently the servant complained of giddiness and sickness, and whilst rendering assistance, the master himself, with the mistress and five children, followed in the train; the sickness continuing for half an hour.

I remain, dear Sir, yours truly,
W. BARTLETT.