TABLE 150.-Corrections to be applied to saccharimetric readings of levulose solutions when a constant normal weight is used

[Normal weight at 20° C 18.407 g; normal weight at 25° C = 19.003 gm)

1 In order to avoid constant repetition of the negative sign, the polarizations of levulose are considered positive. The positive signs in the above table indicate that the negative polarizations of levulose are to be increased to higher negative values.

XXXVII. APPENDIX 2.-RÉSUMÉ OF THE WORK OF THE INTERNATIONAL COMMISSION FOR UNIFORM METHODS OF SUGAR ANALYSIS

ALEXANDER HERZFELD, chairman; F. G. WIECHMANN, American Secretary

FIRST SESSION [1] HAMBURG, GERMANY, JUNE 12, 1897

1. Kinds of quartz plates to be selected. At the start, only quartz plates of high polarizing value shall be tested; later, however, such also as will cover the entire scale range of saccharimeters.

2. Method of examination of quartz plates.-Their examination is to be conducted in the same manner as has been done heretofore by the Commission of Trades Chemists under guidance of the Society of the Beet Sugar Industry of the German Empire, with the participation of the Imperial Normal Testing Bureau and the Physical Technical Reichsanstalt.

3. Temperature to be adopted as the normal temperature for polarization.—For the examination of quartz plates 20° C is to be chosen as the normal temperature, and the metric liter is to be adopted. The normai weight to be adopted is hence to be 26.00 g, where 26.048 g is the normal weight valid for Mohr's liter at the temperature 17.5° C.

4. Additional methods and means suggested in order to decrease differences in polarization work. In consideration of the well-known difficulties in sampling bagged sugar, sampling each bag does not offer sufficient advantages to justify a departure, in the interests of trade, from the customary method of sampling 20 bags in every 100 bags.

5. Desirability of an endeavor to introduce uniformity of analytical methods for beet-sugar work in all countries concerned. Such an endeavor shall be made. For the computation of sugars, analyses shall be admissible only of such chemists as shall have pledged themselves to execute the analysis of sugar in accordance with the methods prescribed by the International Commission.

6. The determination of invert sugar.-The determination of invert sugar is to be made only in solutions which have been clarified with lead solution and from which the lead has then been removed. If volumetric determinations are made, the amount of reduction due to the chemically pure sucrose must be deducted.

SECOND SESSION [2] VIENNA, AUSTRIA, JULY 31, 1898

1. Results of the international examination of quartz plates.-In general, such examinations proved satisfactory. Certain discrepancies were undoubtedly due to the fact that the examinations had not always been made at 20° C, as prescribed. Reference was made to the observations of Herzfeld, Wiechmann, and Wiley that pressures, due to varying temperatures affecting their mountings, exercise an influence on the rotation values of fixedly mounted quartz plates and quartz wedges. Whereas the quartz plates heretofore used-owing to the fact of their being firmly held in their mountings are apt to be strained when their temperature is raised, and whereas such strains cause irregularities in the polarizing values of these plates, it was resolved that the investigation above referred to should be repeated, making use of other quartz plates not subject to the defect mentioned. On the motion of Messrs. Dupont and Jobin it was resolved to employ plates the rotation values of which shall cover the entire scale of the saccharimeter, one levorotatory and four dextro-rotatory plates, the thickness of which is at the same time to be given, so that the plates shall remain serviceable when the normal weights shall be changed.

In determining the value of the plates there shall be employed not only the normal temperature of 20° C but, on the motion of Messrs. Wiley and Wiechmann, also of 30° C, in order to take into due account the condition of warmer countries. In employing apparatus with quartz-wedge compensation the changes shall be studied which the saccharimeter itself suffers in consequence of variations of temperature. As source of light there shall be employed only yellow sodium light or light sufficiently purified by ray filters.

Upon the motion of Dr. Hermann, of Hamburg, it was furthermore agreed to emphasize specifically in the protocol that the commission had thus far made no such changes in the normal weight for polariscopes which could influence the results of polarization in the least. This had been mentioned already in the protocol of the Hamburg session of June 12, 1897.

2. Desirability of examining raw beet sugars for trade purposes according to the inversion method.-Those present were unanimously of the opinion that the question should, in general, be decided in the negative. Exception should be made only in case of the products obtained in making sugar from molasses; with these it was recommended to make determinations of sugar and of raffinose.

3. Discussion of applications of the Deutsche Zucker Export Vereine.-Dr. Hermann suggested that uniformity in analytical methods should even now be striven for as much as possible, and the presiding officer was requested to prepare, with the assistance of the members of the commission, a clear compilation of analytical methods which are in vogue in the different countries, and also to prepare a résumé of the directions which are to be followed in cases of differences in analysis. Basing on these documents, the attempt shall be made to secure international acceptance of a uniform method of procedure.

THIRD SESSION [3] PARIS, FRANCE, JULY 24, 1900

1. Normal sugar weight to be adopted for saccharimeters of German make when the metric flask is used.-The Imperial Physical Technical Institute has, by its communication dated October 19, 1898, called attention to the fact that an exact conversion of the normal weight 26.048 g for Mohr's cubic centimeters at 17.5° C corresponds to 26.01 g (not 26.00) metric volume at 20° C, determined in air with brass weights.

The commission decided that in consideration of the insignificance of the deviation the normal weight of 26.00 g shall henceforth be adopted for 100 metric cubic centimeters at 20° C, determined in air with brass weights.

2. Examination and disposal of quartz plates.-Prof. Herzfeld reported briefly on the results of the examination of quartz plates, and the commission agreed that these quartz plates should be divided among the nations represented. For the United States, the plates were to be sent to the Department of Agriculture, at Washington; for France, to the Syndicate of Sugar Manufacturers; for Belgium, Holland, Austria-Hungary, and Russia, to the associations of sugar manufacturers represented in the session by delegates.

3. General principles governing the adjustment of saccharimeters.-On motion of Messrs. Camuset and Saillard, the following was adopted:

"The convention declares it to be necessary that the rotation of chemically pure sugar be accepted as the fundamental basis in saccharimetry.

"The chemically pure sugar which is to be employed for this purpose shall everywhere be prepared according to the same method, which is as follows (method of the English chemists):

"Purest commercial sugar is to be further purified in the following manner: A hot saturated aqueous solution is prepared and the sugar precipitated with absolute ethyl alcohol, the sugar is carefully spun in a small centrifugal machine and washed in the latter with some alcohol. The sugar thus obtained is redissolved in water, again the saturated solution is precipitated with alcohol, and washed as above. The product of the second centrifugaling is dried between blotting paper and preserved in glass vessels for use. The moisture still contained in the sugar is determined and taken into account when weighing the sugar which is to be used."

The convention furthermore decided that central stations shall be designated in each country which are to be charged with the preparation and the distribution of chemically pure sugar. Wherever this arrangement is not feasible, quartz plates, the values of which have been determined by means of chemically pure sugar, shall serve for the control of saccharimeters.

Mention should be made of the fact that in the discussion on this topic it was remarked, on the one hand, that the preparation of chemically pure sugar is not an easy task, and that in countries having hot climates sugar is dried with difficulty and hence is not stable and hardly available for transportation. Thereupon it was pointed out that the above control, by means of chemically pure sugar, should, as a rule, apply only to the central statio s which are to test the correctness of saccharimeters; for those who execute commercial analyses, the repeated control of the instruments is to be accomplished, now as before, by means of quartz plates.

Concerning the working temperature, the following resolution of Mr. François Sachs was unanimously adopted:

"In general, all sugar tests shall be made at 20° C.

"The adjustment of the saccharimeter shall be made at 20° C. One dissolves (for instruments arranged for the German normal weight) 26.00 g of pure sugar

in a 100-metric cubic centimeters flask,47 weighing to be made in air, with brass weights, and polarizes the solution in a room, the temperature of which is also 20° C. Under these conditions the instrument must indicate exactly 100.00. "The temperature of all sugar solutions to be tested is always to be kept at 20° C while they are being prepared and while they are being ploarized.

"However, for those countries the temperature of which is generally higher, it is permissible that the saccharimeters be adjusted at 30° C (or at any other suitable temperature), under the conditions specified above, and providing that the analysis of sugar be made at that same temperature."

Objections were raised against the universal normal weight 20.00 g by Mr. François Sachs as well as by Mr. Strohmer. In consequence, it was resolved not to undertake the introduction of the same, but to adopt the resolution:

"The general international introduction of a uniform normal weight is desirable."

It was furthermore resolved, on the basis of the proposition of Mr. Strohmer, to observe the following rules in raw sugar analysis:

I. POLARIZATION

In effecting the polarization of substances containing sugar, half-shade instruments only are to be employed.

During the operation the apparatus must be in a fixed, unchangeable position, and so far removed from the source of light that the polarizing nicol is not warmed by the same.

As sources of light there are to be recommended lamps with intense flame (gas triple burner with metallic cylinder, lens, and reflector; gas lamp with Auer burner; electric lamp; petroleum duplex lamp; sodium light).

The chemist must satisfy himself, before and after the observation, of the correctness of the apparatus (by means of correct quartz plates) and in regard to the constancy of the light, he must also satisfy himself as to the correctness of the weights, of the polarization flasks, the observation tubes, and the cɔver glasses. (Scratched cover glasses must not be used.)

Several readings are to be made and the mean thereof taken, but any one individual reading must not be selected.

II. SUGAR ANALYSIS

1. Sucrose. To make a polarization, the whole normal weight for 100 cc is to be used, or a multiple thereof for any corresponding volume.

As clarifying and decolorizing reagents there may be used: Subacetate of lead, prepared according to the German Pharmacopoeia (three parts by weight of acetate of lead, one part by weight of oxide of lead, ten parts by weight of water), Scheibler's alumina cream, concentrated solution of alum. Bone black and decolorizing powders are to be absolutely excluded.

After bringing the solution exactly to the mark and after wiping out the neck of the flask with filter paper, all of the well-shaken, clarified sugar solution is poured upon a dry, rapidly filtering filter. The first portions of the filtrate are to be thrown away and the balance, which must be perfectly clear, is to be used for polarization.

2. Water. In normal beet sugars the water determination is to be made at 105° to 110° C.

For abnormal beet sugars, there is no commercial method for the determination of water.

3. Ash.-To determine the ash content in raw sugars the determination is to be made according to Scheibler's method, employing pure concentrated sulphuric acid. For an ash determination at least 3 gr. of the sample are to be used. The incineration is to be carried out in platinum dishes, by means of platinum or clay muffles, at the lowest possible temperature (not above 750° C).

From the weight of the sulphated ash thus obtained 10 percent is to be deducted and the ash content, thus corrected, is to be recorded in the certificate. 4. Alkalinity.-As, according to the most recent investigations, the alkalinity of raw sugars is not always a criterion of their durability, the commission abstains from proposing definite directions for the execution of the investigations.

5. Invert sugar. The quantitative determination of invert sugar in raw sugars is to be made according to the method of Dr. A. Herzfeld. (Zeitschrift des Vereins für die Rübenzucker-Industrie des Deutschen Reiches, 1886, pp. 6 and 7.) Furthermore the following resolutions were adopted.:

47 Or during the period of transition, 26.048 g in 100 Mohr's cubic centimeters.

The commission declares that only well-closed glass vessels will insure the stability of samples.

To obtain correct results it is desirable that the samples contain at least 200 gr. of material.

All of the above resolutions were adopted unanimously by those present.

FOURTH SESSION [4] BERLIN, GERMANY, JUNE 4, 1903

1. Professor Herzfeld outlined the previous work of the commission. The sets of quartz plates which had been selected by the Physikalisch-Technische Reichsanstalt in Berlin, and which had been tested in the laboratory of the Verein der Deutschen Zuckerindustrie as to their sugar value, have been distributed to proper central stations of the countries interested, and there kept at the disposal of chemists. These plates have been tested in almost all of the countries which have received the sets, and have been found correct. Some of these stations have thus far not made a report as to the result of this reexamination, and such a report is therefore requested.

Execution of the Paris agreement, according to which chemically pure sugar is to be used for the adjustment of polariscopes and for the testing of plates, has in some countries met with difficulties because they could not succeed in preparing chemically pure sugar. The laboratory at Berlin, therefore, offers to furnish chemically pure sugar.

In the determination of invert sugar a difficulty has arisen, inasmuch as the English chemists have of late again declared against the clarification with basic lead acetate; the commission will therefore have to seek means and methods to prevent, in this respect, loss of uniformity now secured in the methods of analysis. The day's proceedings furthermore covered reports concerning:

I. Practical experiences made with the uniform methods of analysis agreed upon in Paris.

II. The valuation of "sand" and "krystallzucker" in international trade. III. Introduction of international uniform directions for sampling raw sugars. IV and V. Influence of temperature on the specific rotation of sucrose, and introduction of temperature-corrections when the temperature of observation differs from the temperature of 20° C, which has been accepted as the normal temperature.

VI. Determination of the sugar subject to duty or bounty contained in saccharine products and fruit preserves.

VII. Chemical control as an aid to the "entrepôt" system, sanctioned by the Brussels Convention.

FIFTH SESSION [5] BERN, SWITZERLAND, AUGUST 3 AND 4, 1906

1. The chairman in a review of the achievements of the commission designated the duties of the commission to be purely analytical.-The commission has for its object the regulation of the methods of sugar analysis and endeavors to secure the working of chemists according to uniform and the best methods, but the commission does not undertake to establish trade customs. The commission does not recognize resolutions carried by majority vote; it is in fact necessary that at least the representatives of the most important countries interested in sugar be in accord on a question before the same is presented for acceptance, as otherwise no reliance can be placed on the recognition of the resolutions by chemists.

2. Determination of a method of preparing Fehling's solution as well as the manner of making invert-sugar determinations.-Messrs. Watt and Wiechmann communicated the results of their investigations. Mr. Watt preferred the volumetric method, Mr. Wiechmann the gravimetric method for commercial analyses. The latter moved that clarification with basic lead acetate shall be obligatory for the examination of sirups. This recommendation was indorsed by Messrs. Watt and Prinsen Geerligs and thereupon also by the entire commission.

The chairman reported on tests made for the comparison of Violette's and Fehling's solution, which had not yet been completed. He announced that Mr. Munson, the chairman of the Association of American Agricultural Chemists had, through intervention of Mr. Wiechmann, sent him a resolution of the association named, wherein the same expressed the wish to work hand in hand with the commission in the matter of securing a uniform alkaline copper solution.

Mr. Pellet also presented a paper on this subject, which was published in the Sucrerie Indigène, as well as in the Deutsche Vereinszeitschrift.