at 100-105°C., was weighed as Mg(NH4) AsO4, H2O. If the initial step in the above method be reversed, that is, the caustic alkali added to the hot solution of the ferric arsenate, somewhat less accurate results are obtained, owing to the retention of some of the arsenic by the iron precipitate in the form of a basic compound.

Method III. Since it has recently been shown (Rosenthaler, Zeitschrift f. analyt. Chem., 1906, 45, 596) that, under well-defined conditions, arsenic acid may be very accurately estimated volumetrically by an iodometric method, it was deemed of interest to ascertain its applicability in the analysis of soluble iron arsenate. This method naturally permits of the indirect estimation of the iron in an analogous manner, by determining the amount of iodine liberated from a solution of potassium iodide. In the case of arsenic acid the reaction is stated to be completely effected in the cold in ten to fifteen minutes, provided a large amount of free hydrochloric acid is present, and may be expressed by the following equation:

HзASO1 + 2KI + 2HCl = H3ASO3 + I2 + 2KCl + H2O. In employing this method the iron and arsenic were initially separated by both the above described methods, I and II, in order to compare the results.

(a) Separation of the Iron and Arsenic by Method I.-The solution of arsenic acid, obtained as described under Method I, was brought into a glass-stoppered bottle having a capacity of about 100 c.c., and 2 Gm. of potassium iodide added, together with such an amount of hydrochloric acid that the liquid would contain about 20 per cent. of HCl. Any slight precipitate that is thus produced is redissolved by the addition of the smallest possible quantity of water. After being allowed to stand for ten minutes at the ordinary temperature, the liberated iodine was titrated with a standardized solution of sodium thiosulphate with the use of a little light petroleum to indicate the end of the reaction. For the estimation of the iron, the filtrate and washings from the precipitate of arsenous sulphide, obtained as described under Method I, were concentrated, and, after oxidation with nitric acid, the iron was precipitated by means of sodium hydroxide. The ferric hydroxide was collected on a filter, washed, dissolved in 10 c.c. of hydrochloric acid, and the solution diluted to the measure of about 50 c.c. This was transferred to a glass-stoppered bottle having a capacity of about 100 c.c., 2 Gm. of potassium iodide added, and, after stand

ing for half an hour at a temperature of 40-50°C., the cooled liquid was titrated with a standardized solution of sodium thiosulphate, using starch as an indicator.

(B) Separation of the Iron and Arsenic by Method II.-The precipitate of ferric hydroxide obtained by adding a solution of the soluble iron arsenate to a solution of sodium hydroxide was treated in precisely the same manner as described in connexion with the corresponding precipitate under (a), the iron being finally estimated indirectly by titrating the liberated iodine with a standardized solution of sodium thiosulphate. For the estimation of the arsenic, the alkaline filtrate and washings from the above-mentioned precipitate of ferric hydroxide were concentrated, neutralized with hydrochloric acid, and subsequently such an amount of the latter added that the liquid would contain about 20 per cent. of free HCl. The process was then conducted in precisely the same manner as described under (a). The results of these determinations of the arsenic in Soluble Iron Arsenate were as follows:

Method I.-1.0284 Gm. of the salt gave 0-3480 Gm. Mg(NH4)AsO4, H2O, corresponding to 13-33 per cent. As. Method II.-0.9449 Gm. of the salt gave 0-3188 Gm. Mg(NH)AsO4, H2O, corresponding to 13-29 per cent. As. Method III.-Volumetric.

(a) The arsenical solution from 0.8922 Gm. of the salt liberated an amount of iodine equivalent to 31 c.c. Na2S2O3 (1 c.c.0-0125 I), corresponding to 12.83 per cent. As.

(8) The arsenical solution from 0.9970 Gm. of the salt liberated an amount of iodine equivalent to 35.2 c.c. Na2S2O3 (1 c.c. = 0·0125 I), corresponding to 13-04 per cent. As.

From a comparison of these figures it may be concluded that the simple method of assay designated as II affords results which are sufficiently accurate for technical purposes, and that, when a standardized solution of sodium thiosulphate is available the assay may be still furthur expedited by the volumetric determination of the iron and arsenic, as described under Method III (8).

Although the composition of this salt is naturally subject to slight variations, if it be assumed to contain an amount of arsenic ranging from 13 to 13.5 per cent., this would correspond, approximately, to from 34 to 35 per cent. of anhydrous ferric arsenate. The proportion of iron, with consideration of the calculated excess of the latter, would consequently correspond

to about 11 per cent., but the adoption of a standard for this element is obviously of very much less importance than the control of the arsenical content of the preparation.

The Wellcome Chemical Research Laboratories, London.

Mr. W. DUNCAN, in a few observations, mentioned that eight years ago he read a paper on this subject, and had recommended that ferric arsenate should take the place of the present ferrous arsenate, and he doubted whether any suggestion to introduce a mixture of sodium ferryl arsenate and sodium ferryl citrate would be an improvement.

Mr. FINNEMORE said the test which the authors of this paper ascribed to Rosenthaler (Method III) was, he believed, first discovered by Mr. Naylor in 1870-75. It had been "rediscovered" since then, but the original test was introduced by Mr. Naylor.

The PRESIDENT (to Mr. Duncan): May I ask if your preparation was consistent in its arsenic content?

Mr. DUNCAN The salt I suggested has the composition FeAsO,H2O.

Mr. CowIE explained that he had found that ferric salts passed back to the ferrous state to some extent in these combinations with organic acids which were being discussed.

STANDARDS FOR ALKALOIDAL DRUGS AND THEIR

FLUID EXTRACTS.

BY J. C. UMNEY, F.C.S., AND C. T. BENNETT, B.SC., F.C.S.

Progress in the revision of the British Pharmacopoeia now makes it necessary to give most careful thought to the processes of assay of potent vegetable drugs and consideration to the desirable strength of galenicals prepared from them. In the ordinary routine work of a wholesale druggist's laboratory much information is necessarily collected on such points, and we have thought that a communication on this important question to the Conference will be of interest and at the same time elicit opinions from other workers that cannot fail to be of value to the Pharmacopoeia Reference Committee now entrusted with the most important work of revision. Taking as an up-to-date guide the new United States Pharmacopoeia, we have noted in

LL

tabular form the drugs official in the United States Pharmacopoeia of 1905 that have active-principle standards, with the corresponding ones in the British Pharmacopoeia, 1898, where they exist, and also the standards already suggested by one of us in "Standards for Medicines" (see P.J., November 15, 1902, p. 495). It should be noted that since the publication of the United States Pharmacopoeia many alterations have been made in the active-principle standards, arising from the working of the new (American) National Food and Drugs Act of 1908, and from the considerable rejections of imported drugs by the New York Customs authorities. One appreciates the desirability of fixing standards for drugs as high as possible, but it must be done with due regard to natural variations in them from season to season. In order to show the natural variation of alkaloidal strength in crude drugs, and in that way to indicate as far as possible what limits are suitable ones, taking one season with another, we have set out the percentage of alkaloids in different samples of the drugs examined over a period of three years. It will be seen that the variations are very considerable, and in some cases of great importance. A few seasons ago practically no belladonna root was obtainable in commerce containing more than 0.3 per cent. of alkaloids, whilst at the present time the roots available in commerce contain as much as 0.55 per cent. The variation also in coca is enormous, but a normal average may be taken as being 0.5 per cent. Cinchona barks also vary greatly, and we have had to reject a large number as being outside the B.P. limits. Ipecacuanha is fairly uniform, and generally yields from 2.0 to 2.5 per cent. of alkaloid soluble in chloroform.

The table, on page 516, includes the liquid extracts standardized in the new U.S.P., together with the standards corrected since the publication of the Pharmacopoeia, and the standards of the British Pharmacopoeia, 1898. We should say that it is extremely doubtful whether liquid extract of aconite will be included in the new British Pharmacopoeia, but there does seem a demand for a fluid extract of colchicum seeds, conium fruit, and, possibly, of guarana, all of which admit of ready standardization. With regard to henbane, the standardization does not seem to be of such great importance, as the drug does not depend alone for its valuable medicinal properties on the mydriatic alkaloids that it contains. We certainly think that it would be desirable to introduce a standardized

Leaf, 0.448.