and therefore so far has failed in giving a satisfactory answer to the query submitted to him, yet perhaps the observations which he has thrown together may prove of some interest, and will be accepted instead.

The subject, then, may be considered both in a chemical and pharmaceutical point of view, and first we will briefly allude to the pure salt in solution before entering on the main inquiry.

Solution of acetate of ammonia was first described by Boerhave, in 1732. It was also introduced into medical use by him. He prepared it in a similar manner to that followed now, by saturating the purest vinegar with carbonate of ammonia. Subsequently, Minderer, a Scotch physician, by bringing it further into notice, claimed the honor of its discovery, and the solution was hence known as "Spiritus Mindereri."

The difficulty of preparing a neutral solution, as well as the uncertainty of its strength, was early observed; and in 1773 Baume endeavored to obtain the solid salt by concentrating the solution. In this he failed, having to encounter the difficulty of the salt being readily decomposed by heat while in a moist state, the ammonia being first given off, and subsequently the acetic acid. Berzelius, by uniting equal weights of dry sal ammoniac and acetate of lime, and subliming by a carefully regulated temperature, obtained the dry salt by double decomposition.

In a pure state, acetate of ammonia is a white crystalline salt, easily deliquescing in a damp atmosphere. If this dry salt be dissolved in hot water to full saturation, and enclosed in flasks, upon cooling slowly the pure salt crystallizes in long acicular crystals. In this state it appears to have an acid reaction.

To prepare the solution of the salt, however, more directly, its constituents may be immediately combined :-solution of acetic acid and solution of ammonia. If these are pure and the mixture rendered perfectly neutral, the solution may be considered pure. In this state it is not a permanent salt, except in perfectly full bottles, hermetically closed. In partially full vessels at ordinary temperatures it gradually changes, the

acetic acid becoming decomposed, vinegar animalcules appearing, and the solution becomes alkaline, carbonate of ammonia being thus generated.

The medicinal solution of acetate of ammonia,-liquor ammoniæ acetatis, or spirit of Mindererus,—is directed to be made, by our National Pharmacopoeia, by saturating dilute acetic acid with carbonate of ammonia; and it is ordered, when dispensed, to be freshly made, the solution then containing a portion of the liberated carbonic acid gas.

In regard to the exact amount of each of the constituents to be employed in the above process, it happens unfortunately that neither of them is found in any very definite state of composition.

The sesqui-carbonate of ammonia, varying continually from exposure, absorbing carbonic acid and losing ammonia, becomes a bi-carbonate, so that only the translucent pieces in the interior of a lump have any very near approach to a definite chemical compound. The acetic acid, although permanent, is made with little uniformity, and its strength can only be ascertained by chemical tests. It follows, therefore, in carrying out the directions of the Pharmacopoeia, we are under the necessity of falling back on that responsible, and, to many, vague phrase, q. s. ad saturandum. As the amount of salt in this solution depends entirely upon the strength of the acetic acid employed, apothecaries should be aware that acid of a proper strength is not readily obtained. Acetic acid No. 8, sp. gr. 1.047, is rarely met with; the article usually called No. 8 being generally only No. 6,-i. e., one pint to make six of officinal dilute acetic acid. The precaution, therefore, of diluting to a lesser extent when weaker, should be strictly observed.

of

The acetic acid employed in this preparation should be entirely free from empyreumatic odor, derived from the pyroligneous acid, from which it is generally obtained. If free from this and other impurities, it should be diluted with pure water until its density be reduced to 1.007 at 60° F.; the ordinary No. 8 acid requiring about five times its bulk of water to dilute it sufficiently. In taking the specific gravity of liquids varying little from the density of water, particular care should be

observed in reducing the temperature of the liquid to 60° F. Otto's acetometer will, however, be found a more reliable method of determining the strength of acetic acid,—the principle of which is, neutralizing the acid with a normal solution of ammonia; the quantity of the ammonia employed indicating directly the percentage of the acetic acid,-assuming that 100 grains of the officinal dilute acetic acid must saturate 7.6 grains of cryst. bi-carbonate of potassa. This will be equivalent to 4:55 per cent. of mono-hydrated acetic acid, (Wood & Bache give 5 per cent. as the strength). Acid of this percentage has a specific gravity of 1.0068 at 60° F., when accurately taken.

Having the acetic acid properly diluted, the directions of the Pharmacopoeia are to add the carb. ammonia gradually to the acid, until this is saturated. It is just here that a practical difficulty occurs, in determining the exact point of saturation. At first the taste will sufficiently indicate if the solution is yet acid, but as the point of saturation is approached, litmus paper or solution of litmus must be resorted to. These, if proper precautions are taken, will give sufficiently accurate results. It will be observed, in testing liquids containing free carbonic acid, that litmus will be reddened, even after the solution is neutralized by an alkali. This reddening, however, is not permanent, but will disappear upon drying the paper, the carbonic acid going off with the moisture. This source of fallacy may also be overcome by gently warming a portion-say half an ounce of the solution, to which a few drops of the solution of litmus has been added. The red color of the solution will gradually change to a violet, indicating the fact of its alkalinity. If now dilute acetic acid be dropped in until the color is slightly reddened, the number of drops required will give the proportionate amount of acid to be added to the remainder of the solution. If, on the contrary, the solution when heated should remain red, aqua ammoniæ should be dropped in until the color just begins to change, the number of drops indicating, as before, the amount requisite for the whole solution.

It has been proposed, in order to avoid in a measure the uncertainty above alluded to, to saturate the strong acid No. 8 directly with carbonate of ammonia, and afterwards to dilute to the proper degree.

Made in this manner, there is much less difficulty in ascertaining the point of saturation, no carbonic acid being retained in the solution.

The German and British Pharmacopoeias order the liquor ammoniæ acetatis to be made by the union of strong acetic acid and concentrated aqua ammoniæ; the former adding water to the neutral solution until its density becomes 1035. The British Pharmacopoeia employs it undiluted, of specific gravity 1.060; made in this way, the solution is nearly four times the strength of our own. It is also much less liable to decomposition, and no difficulty occurs in preparing it neutral, there being no carbonic acid in the solution. In commenting upon this process, Prof. Bache, alluding to the absence of the carbonic acid in the solution, says, that "a great benefit remedially is gained by its presence, which reconciles the stomach to the medicine, and sometimes even allays vomiting in febrile diseases." With this view of the subject, and believing that the remedial efficacy of a medicine should always be esteemed of the highest importance, and, in fact, as constituting its only value, I suggest the following method of preparing the liquor ammoniæ acetatis; a modification of the officinal directions, yet following strictly its spirit.

A solution of the translucent internal portion of sesqui-carbonate of ammonia is to be made according to the following data:

The pharmacopoeia gives 7.6 grains bi-carbonate of potassa as the quantity necessary to saturate 100 grains of dilute acetic acid, or nearly 34.9 grains per fluidounce. As the equivalent saturating powers of bi-carbonate of potassa and sesqui-carbonate of ammonia are respectively 100-2 and 59, it would therefore require 20 grains of this latter to saturate one fluidounce of dilute acetic acid. The solution of ammonia I make of double this strength, or 20 grains to half an ounce of distilled water, the other half-ounce requiring to be made up of a dilute acetic acid of double the officinal strength. It is in preparing this acid solution of proper strength, that the only practical difficulty lies. The method I have taken is the following: from a pipette graduated into 100 parts and filled with No. 8

acetic acid, I drop sufficient of the acid to neutralize 100 similar parts of the prepared ammoniacal solution. The quantity requisite is noted, and that amount of acid must consequently be made to measure 100 parts, by the addition of sufficient water. Thus, if 30 parts of acid were necessary to saturate 100 parts of the ammoniacal solution, then to every 30 parts of acid add 70 parts of water, and the solution is ready for use. The solutions keep well, and it is only necessary to mix them in equal quantities to produce an effervescent draught of neutral acetate of ammonia, retaining the free carbonic acid so desirable as a remedial agent.

ON VALERIAN.

BY THOMAS DOLIBER.

QUERY 35. Is the cultivated Valerian produced in New England of equal quality with that imported from England and Germany, and are there any characteristic differences by which they may be distinguished?

The Valerian of American and that of English growth were the only varieties with which experiments were made. The American came from Vermont; the English was obtained from an undoubted source. Solid and fluid extracts of each were made, samples of which and also of the roots are herewith submitted. A quantity of each fluid extract was given to several physicians and others, but the reports from them were very vague and indefinite. A few years ago a large manufacturer of fluid extracts prepared some fluid extract of each variety, American and English, and several hundred bottles of each were sent to physicians with a request to test their relative merits. The reports were generally in favor of that prepared from the American root.

As no analysis of either variety was made, I cannot state the relative amount of oil yielded by them, nor can I tell the average yield from the American root, but the oil distilled from it is of very fine quality, and is said by those who manufacture it to surpass that obtained from the foreign growth, both in quality and quantity. The amount of oil in the latter varies, according to different authorities, from 37 to 2 per cent.