摘要:

APRIL, 1909. THE COMPOSITION OF CIDER. Vol. XXXIV., No. 397. BY B. T. P. BARKER, M.A., AND EDWARD RUSSELL, B.Sc., F.T.C. (Rend at the Meeting, Ma& 3, 1909.) THE efforts which have been made, with considerable success, during the past decade or so to popularise cider as a beverage have been handicapped greatly by the fact that there is no legal definition of cider in this country. Owing to this, much so-called “cider” has been placed without check on the market, and this, by its unsatisfactory character, has prejudiced seriously the sale and repute of the genuine article. In certain instances no apple- juice whatever has entered into the composition126 THE ANALYST. of the liquid, while in other cases the proportion of apple-juice has been extremely limited. The deficiencies in character and flavour of such productions have been made good by additions of flavouring essences, sugar, or artificial sweetening agents, supplemented usually by some preservative, which, certainly in many cases, has been used by the maker without regard to the strength of the dose, and with entire ignorance of its chemical and physiological properties.Thus Lloyd (“ Annual Report of the National Fruit and Cyder Institute,” 1905, p. lo), for instance, found in certain samples as much as 40 grains of salicylic acid per gallon. While cider- makers of repute are by no means agreed as to the legitimacy of additions of water, sugar, and other natural constituents of apple-juice, or even of limited amounts of certain preservatives, it is not disputed that unchecked additions of any sort are undesirable.I n the absence of a legal definition of cider, little can be done to improve the present state of affairs, except in extreme cases in which the Merchandise Marks Act or the Food and Drugs Act may be brought into action. Durham (Jozmzal of the Royal Imtitute of Public Health, May, 1908) has pointed out, where definition of materials and mode of manufacture is not enough to prevent adulteration and falsification, some form of chemical standardisation is essential on the part of any definition proposed. Considerable attention has been given to this subject in France, and Durham (Zoc. cit.) summarises the legal position of cider in that country as follows: “No drink may be sold as cider unless it is the product of fermentation of the juice of fresh apples, unless it contains a certain proportion of certain chemical constituents, and unless not less than a given proportion of apples has been used to produce a given volume of fluid.Moreover, it must not contain any artificial sweeten- ing chemicals, such as saccharine ; it must not contain chemical flavouring additions ; the employment of certain antiseptics (as sulphurous acid) may be permissible within dt?Jint?d limits, or entirely prohibited (as borate preparations). Artificial colouring agents are likewise prohibited.” Dealing with the essential chemical criteria for estimating quality and genuineness, the actual judgment appears to be based upon the amount of alcohol (real and potential), extract dried a t 100’ C. free of sugar, and ash. The permissible minima vary in different localities, and sometimes in different seasons.The Paris Municipal Laboratory gives the following minima : ... Total alcohol by volume ... ... 3.0 per cent. Extract dried at 100” C. ... ... ... 18.0 grams per litre. Ash ... ... ... ... ... 1-7 ,, ,> Alcohol . , . ... ... ... ... 3.0 per cent. Extract ... . . . ... ... ... 9.0 grams per litre. Ash ... ... ... ... ... 1.2 ,, ,, The Association Frangaise Pomologique gives a lower standard, viz. : By the regulations of July 20, 1908, the definition of cider and porry in France has been determined as follows : “ No drink is to be sold (1) under the name of cider unless it is derived exclu- sively from the fermentation of the juice of fresh apples, or a, mixture of freshTHE ANALYST.127 apples and pears extracted with or without the addition of water ; or (2) under the name of ‘ perry ’ unless it is derived exclusively from fresh pears with or withou water. The term cidre pur jas or poire pzir jus is reserved for cider obtained without the addition of water. The term ‘ cider’ or ‘Perry’ is reserved for cider or perry containing at least 3.5 per cent. of alcohol, 12 grams per litre of extract (sugar deducted), 1.2 grams of mineral matter (ash) per litre. Cider or perry falling below these limits is to be called petit cidre or petit poire.” A chemical standard of composition has also been given by the American Association of Agricultural Chemists as follows : Alcohol (maximum) ... ... ... 8.0 per cent. Extract (minimum) ...... ... 1.8 ,, ,, Ash (minimum) ... ... ... ..I 0.2 ,, ,, Durham quotes the results of his analyses of five ciders, the first three being made by different makers and purchased in the open market, the fourth made from picked and stored fruit, and the fifth prepared by the ‘L diffusion ” method : 1. 2. 3. 4. 5. Alcohol. .. ... 2-83 3.56 4.7 8-00 5.00 Extract ... 13-50 15-48 28.0 20-04 20.68 Ash ... ... 1.52 3.08 2 -8 2.64 2-44 From these figures he deduces that (1) has been heavily watered; that (2) has probably been somewhat watered, and a neutralising agent added to arrest excessive acidity ; and that (3) has probably had some addition of ‘‘ body-giving ” substances. Presumably from the author’s knowledge of (4j and (5) the results may be taken as obtained from genuine pure ciders of special type.He suggests that for the purposes of a definition of cider, the minimum chemical composition as regards alcohol, extract, and ash should be : Alcohol ... ... ... ... 3 or 4 per cent. (by volume). Extract ... ... ... ... 18 grams per litre. Ash ... ... ... ... 1.8 to 2-0 grams per litre. Embrey (ANALYST, 1891, 16, 41) assigns the following composition to American and English ciders, of which the first three are American : 1. 2. Specific gravity ... 1034.28 1033.48 Alcohol ... ... 2.91 3.49 Glucose ... ... 7-91 8.2 As; ... ... 0.3 0.32 Total extractions.. . 9.2 9.6 Acidity (volume) ... 0.096 0.048 (fixed) ... 0.33 0.671 3. 1032.35 2-45 6.93 0.128 0.712 0.24 8.96 Perry. 4. 1010*0 3.64 0.36 0.222 0.244 0-3 4.5 5 .1024.48 3-32 3.86 0.144 0.244 0.34 6.7 He holds that the ash of genuine ciders falls between 0.25 and 0-35 per cent., The addition of water, The number of samples examined hardly warrant so positive a conclusion as that and is disposed to fix these as the highest and lowest limits. he considers, will be evidenced by a fall below the minimum figure. stated,128 THE ANALYST. Allen (ANALYST, 1902, 27,183) made a number of analyses of English ciders, the specific gravities of which varied between 1-002 and 1.032; the original solids between 11.4 and 20-6 per cent.; the sugar-free extractives (as calculated by the deduction of glucose from total extractives) between 0.55 and 3.97 grams per 100 C.C. ; and the ash between 0.22 and 0.41 grams per 100 C.C. While his results are interesting as showing the composition of certain ciders, they cannot well be used to form the basis of a standard of chemical composition, since, apart from internal evidence, there is apparently no means of distinguishing how many, or which, of the ciders were really genuine. Grignon (Le Cidre, Paris, 1887) has published the results of a large number of analyses of French ciders of various types, the actual figures as given by him representing the composition of pure juice ciders only.The following table gives the extreme and mean composition of sixty-four ciders : Minimum. Maximum. Average. Total alcohol volume, per cent. ... ... 3.8 8.00 6.00 Extract (sugar-free), per cent. ... ... 1.71 4-50 2.47 Ash, per cent. ... .. ... ... 0.17 0.35 0.27 Many other French chemists, including Leschartier, Andouard, Jay, Kayser, and Rocques, have published analyses of French ciders of various types. Their results, like those of Grignon, show considerable variations in the quantities of the individual constituents in different cases.It will suffice for present purposes if a few of the results only illustrating typical variations are referred to. Leschartier (Compt. rend., ciii., 1104), studying the variations in composition of ciders made in different districts, found that the limits for total alcohol were 5.1 and 8-9 per cent., for total sugars 0.12 and 7-83 per cent., for sugar-free extract 1.23 and 3-45 per cent., and for ash 0-170 and 0.491 per cent. Obviously, if any value is to be attached to the results of the other authorities already considered, there must have been several ciders amongst those examined by him which could have no claim to be considered as pure juice ciders, The maximum, minimum, and mean results for a number of authentic ciders examined by the Laboratoire Municipale de Paris (Rocques, Le Cidre, Paris, p.128, 1899) were found to be as follows for ciders made in the department of Calvados : Bfaxiinum. Miniinurn. Mean. Specific gravity ... ... ... ... 1.041 1.0012 1.0159 Total alcohol, per cent. ... ... ... 6.5 3.5 5.2 Sugar-free extract, per cent. ... ... 6.46 2-262 3.39 Total sugar, per cent. ... ... ... 6.08 traces 2.162 Ash, per cent. ... ... ... ... 0.432 0.248 0.326 Alkalinity of ash (as K2C03), per cent. ... 0.368 0.204 0.256 Kulisch (Lundw. Juhrb., 19, 83) investigated the composition of a number of German ciders, and found the maximum and minimum limits of various constituents as follows : Minimum. Maximum.Specific gravity ... ... ... ... ... ... 0-9977 1.050 Alcohol, per cent. (by volume) ... ... ... 5.4 7.3 Extract (including sugar), .per cent. ... ... 1.9113 3.023 Sugar, usually in very limited amounts, per cent. ... ... 0.1 0 3 ... ... ... Ash, per cent. . .- ... ... 0.225 0.336THE ANALYST. 129 The figures for alcohol, extract, and sugar represent the normal quantities of those constituents in typical German ciders, which are as a rule almost completely fermented. The amount of alcohol may be much greater in special cases, where the original juice was much richer in sugar than in the average case. Rocques has also published (Le Cidre, Paris, p.131,1899) the analyses of a number of German ciders, the results of which correspond fairly closely with those of Kiilisch, except in the case of certain sparkling ciders, which contained as much as 11.06 per cent. total extract and 8.34 per cent. reducing sugar, in addition to 6.9 per cent, of alcohol (by volume). Evidently the latter had been fortified with sugar in order to yield the sparkling character in bottle. Alwood, Davison, and Moncure (U.S. Dept. of Agric. BUZZ., 88) have given the analyses of a number of commercial samples of American-made ciders, which show great variations in the amounts of the different constituents ; but these need hardly be considered in detail, since it is clear that many of the samples were not genuine.They also studied the composition of certain ciders made by them under experi- mental conditions and fermented with selected yeasts ; but only a few kinds of juice were used, and the quality in each case was very similar. The average of their results was as follows : Specific gravity ... ... ... ... 1.002 Alcohol, per cent. ... ... ... 5-26 Total sugar, per cent. ... ... ... 0.52 Sugar-free solids, per cent. ... ... 1-69 Hotter (Zeitschrift f. d. laizdw. Versuchswesen in Oestew-eich, 1902) has examined the composition of a number of Steierisch ciders made from different types of apples and under various conditions, in many instances definite percentages of water having been added. His results do not differ greatly from others which have already been quoted, but his examinations of the various constituents of the ciders appear to have been much more complete than in the majority of the cases referred to above.Thus, in addition to the regular constituents, he examined the amounts of nitrogen, glycerine, phosphoric acid, and sulphuric acid present. Of these, phosphoric acid is perhaps the only one likely to be of importance for the questions under consideration. He found that the quantity of phosphoric acid (Pz05) varied between 0.096 and 0-336 per cent.; but he doubted if the amount of this substance could be utilised in estimating the purity of a, sample, since watered juice cider was shown in many cases to possess as much as pure juice cider. It is noticeable, on comparing the results of the work of these authorities, that there are wide variations in the composition of undoubtedly genuine ciders-as wide, indeed, in certain cases, as the variations between some genuine and adulterated samples.Any chemical standard of composition proposed, therefore, must be very low, even as compared with the composition of a cider of average quality, unless it is possible to demonstrate that certain constituents vary but slightly in amount in any ciders, The research, the results of which are dealt with in the present paper, was undertaken primarily with a view of determining what variations of certain individual constituents, particularly total ash, phosphoric acid, and ash alkalinity,130 THE ANALYST. actually did occur in English ciders of widely varying types, the history of which was fully known.The ciders Nos. 1 to 7, Table A, about to be considered, were made in November and December, 1906, at the National Fruit and Cider Institute. Each is made from a single variety of apple, the type selected for examination showing extremes of composition as regards contents of malic acid, tannin, and sugar, in the freshly expressed juice. The history of the treatment of each sample has been recorded from the beginning. Each cider is a pure-juice cider, no water or other substance having been at any time added. The ciders Nos. 8 to 13, Table B, are blends collected from various sources, and represent more the type of cider which finds its way to the market, the extreme characters noticeable in Nos. 1 to 7 having been toned down by suitable blending.Nos. 8 and 9 were made by the same maker, and Nos. 10 and 11 by another maker, while Nos. 12 and 13 were made at the National Fruit and Cider Institute. Each of these also is a pure-juice cider. TABLE A. coun- sellor. 2. Spotted Sweet. 3. Backwell Red. 4. 3 trawberry Norman. a. Sweet 6. mora. Kings ton Black. 1. Frederick. 7. Specific gravity . . . Tannin, per cent. ... Alcohol, per cent. ... Solids, per cent. ... Alkalinity, per cent. . . . Pz05, per cent. . . . Acid, per cent, ... Ash, per cent. ... 1.025 0.45 0.190 4.20 7.85 0-368 0.100 0.020 1.0035 0.31 0.370 6.69 3.00 0.414 0.060 0.020 1.0155 0.35 0.118 5.32 6-75 0,302 0.030 0.025 1 -023 0-42 0.044 2.79 6.74 0.268 0.156 0.013 1.0245 0-27 0-358 3.55 7 -04 0-310 0.020 0.013 1.026 0.22 0.124 3.37 6.68 0.246 0.020 0.022 1.017 0.42 0.050 3.67 5.18 0.396 0-076 0.013 TABLE B.9. 10. 11. 12. 1.3. Specific gravity ... Acid, per cent. ... Tannin, per cent. ... Alcohol, per cent. ... Solids, per cent. ... Alkalinity, per cent.. . . Ash, per cent. ... P,O,, per cent. ... 1.000 0.48 0.264 5.83 2.412 0.322 0.116 0.0153 1.022 0.59 0.260 3.55 6-878 0.342 0.127 0.0230 1.0125 0.32 0.212 4.20 5,740 0.308 0.095 0.0192 1.009 0.33 0.248 4-76 3.920 0.312 0.113 0.0165 1.007 0.34 0.180 5.07 3.880 0-322 0.108 0.0191 1.0075 0-45 0.270 4-82 3.614 0.346 0.026 0.0128 We will now enter upon a consideration of the analytical data given in Tables A and B. The specific gravity, sugar, and total solids practically represent the same constituents. We here have very wide variations-from 2.4 to nearly 8 per cent.THE ANALYST. 131 The range is thus too considerable to help in any way in judging of the purity of a sample, though we regard 2 to 8 per cent.as the normal limits for genuine cider. The higher limit is occasionally exceeded in samples where fermentation has been checked a t an early stage. The relation between volatile and fixed acidity is not given, as it would be of more value in judging of the quality of cider than its purity. Tannin varies from 0.04 to 0.37, the variations being much smaller in Table B. These figures are of value for purposes of comparison, and represent the relative astringencies of the various samples. Alcohol by weight varies from 2-7 to 6.69, and, as in the case of solids, a slightly wider variation than this should be allowed.I t will be thus seen that the organic constituents which we have made the subject of consideration do not assist us in arriving at a suitable standard for cider. The ash varies Erom 0.246 to 0.414 in Table A and from 0.308 to 0.346 in Table B. It is interesting to arrive at a more useful constant, and also to see that average commercial samples come well within the range of the extreme figures given by special kinds. The alkalinity varies from 0.02 to 0.156, and generally follows the acidity. This is not of great value, showing the wide limits of the organic constituents. The phosphoric acid varies again, like the ash, within com- paratively narrow limits, 0.0128 to 0-0250 being the limits obtained in both tables, the range being here finer and more general than in the case of ash.While no attempt will be made here to formulate a standard based upon the results obtained from the examinations of these cidere, taken together with those arrived at by other authorities, it may nevertheless be claimed that they represent the composition of genuine pure-juice ciders of widely different and, in most cases, extreme character, and that the average pure-juice cider may be expected to furnish results which fall within the limits just mentioned. They serve, therefore, as some guide for the estimation of the probable parity, or otherwise, of a sample under examination. With regard to the respective values of the individual constituents for this purpose, the acidity, tannin, and the alkalinity of the ash are by themselves of minor importance; while the amount of total solids or (limiting this factor some- what) the percentage of total sugar is of little weight, unless taken in conjunction with the amount of alcohol.The combination of the two latter items, together with the necessary allowance for volatile acidity, gives the ‘‘ potential ” alcohol, which is a feature of primary importance. The dry extract (sugar-free) would be a valuable constant, provided that standard methods for the determination of total solids and sugars were invariably adopted; but the result depends upon the accuracy of the latter estimations. The amounts of ash and phosphates vary within comparatively small limits, and are therefore of considerable service. A comparison of the standards suggested by the various authorities, quoted earlier in this paper, with the results obtained in our work shows that while they may be of service in limiting the amount of adulteration, they nevertheless leave a considerable scope for sophistication of pure-juice ciders of average quality.Acidity expressed as malic acid varies from 0.22 to 0.59.132 THE ANALYST, ADDENDUM ON THE DETECTION OF SPURIOUS CIDERS. The data as to the composition of cider quoted in the above paper are of service in the examination of a cider suspected of being adulterated, and suffice generally in the event of adulteration to indicate its direction and, in a lesser and more uncertain degree, its extent. I n addition to the usual types of adulterated ciders, certain liquids sold under the name of cider, but absolutely devoid of apple-juice, are sometimes met with. These are purely artificial and manufactured products, being simply sweetened aerated waters flavoured with various essences and acidulated, usually with tartaric or citric acids.While it may be debatable as to the manner and extent to which adulteration may be practised within the limits of the existing law, there is no question that these spurious ‘‘ ciders ” are frauds, if sold under the name of cider, on account of the total absence of apple-juice. Such being the case, if the absence of apple-juice can be demonstrated by any direct test, it is unnecessary to subject them to a complete and detailed chemical examination to prove their character. During the course of certain investigations on the constituents of apple-juice which were being carried out by one of us at the National Fruit and Cider Institute, it was found necessary to be able to recognise the presence of traces of apple-juice in liquids by a simple and rapid test.After many experiments the following method was found to give the most satisfactory and conclusive results. The liquid under examination was reduced by evaporation on a water-bath to one-tenth of its original bulk, 100 C.C. of the original liquid being sufficient for the purpose. The concentrated liquid was then shaken in a test-tube for five minutes with an equal volume of ethyl acetate, and the mixture afterwards allowed to rest until the two liquids had separated. The ethyl acetate extract was then drawn off, and a portion carefully poured on the surface of a few C.C.of lime-water contained in a test-tube. At the junction of the two liquids a clear band of yellow colour was produced in all cases where apple-juice or cider was present in the original sample, whereas the absence of any band of colour indicated the absence of apple-juice. The reaction is due to the forination of a yellow compound by the interaction of lime-water and the tannins and related colouring matters of apple-juice, extracted from the sample by the ethyl acetate. The exact tint of the yellow colour varies somewhat according to the amount of tannins, etc., extracted, and also, apparently, according to the type of apple-juice. If minute quantities are present, and especially if the apple-juice has been taken from apples of high acidity, the test is a pale canary or lemon yellow ; with large quantities of tannin, and particularly if the juice has been derived from bitter-sweet apples, the tint may be a deep orange or light brown.I t is important to note that the band of colour soon disappears, owing probably to the neutralisation of the lime-water by the somewhat acid ethyl acetate extract. The presence of one part of apple-juice in 1,000 parts of the liquid under examination can be determined with certainty by this method ; and in those cases where the proportion of apple-juice is appreciably greater, the concentration of the liquid is unnecessary or only required to a much less extent. The method of conducting the test may be varied slightly by directly shaking together the ethyl acetate extract and lime-water, the yellow colour then being shownTHE ANALYST. 133 by the whole body of the latter, but the results are not generally so clear and decisive as by the above method, especially where traces of apple-juice are being sought.The method may be applied to the examination of doubtful ciders in the form already stated, but time is usually saved by extracting the sample without concen- tration with ethyl acetate. Even heavily watered ciders which contain apple-juice give positive results, as a rule, without concentration, and it is rare that a sample which gives negative results prior to concentration proves to be other than spurious and absolutely devoid of apple-juice. Occasionally the presence of artificial colouring matters in the sample under investigation gives some difficulty, but we have not yet, in the course OE our experi- ence, met with any instances which could not be satisfactorily dealt with by suitable modifications of the method.Ethyl acetate extracts of substances containing tannins, other than apples and pears, have been made and tested similarly, but in each case the ring of colour has been totally different in tint from that given by ciders or perries. DISCUSSION. Mr. F. J. LLOYD said that he had long been of the authors’ opinion that no sta.ndard could be laid down for pure cider. He had found that the variations in the composition of apple-juice were so great as to make this impossible. He thought it right, however, that steps should be taken to put a stop to the sale as cider of artificial liquids devoid of apple-juice, and the question arose as to how one could say with a fair amount of confidence whether apple-juice was entirely absent or whether it was present in small quantity only.I t would be remembered that Allen drew attention to the fact that boric acid was present in all geouine cider. Eittving examined from this point of view a number of samples of cider which he knew to be genuine, he could fully confirm Mr. Allen’s statement, and he considered this to be a valuable test. The fact of the presence of tannin in apple-juice also afforded a means of detecting artificial cider, which did not as a rule contain tannin. Mr. WILLIAM THOMSON asked whether the authors had tested their samples for boric acid, and whether in their opinion its presence might not be regarded as evidence of purity, seeing that boric acid was not found to any appreciable extent in other vegetables.Mr. CHAPMAN remarked that to formulate standards for cider seemed to be merely setting a number of unregenerate persons a very simple problem in synthetical chemistry. The PRESIDENT remarked that the authors had apparently not determined the proportion of potash in the samples. This could be readily done, and, although the results might not turn out to be of much importance as a criterion of purity, the more facts that were obtained the better would seem to be the chance of dealing with artificial substitutes. With regard to the various standards that had been laid down in France and elsewhere, he was afraid that the mere determination of the factors specified would not afford any very reliable indication of the genuineness or otherwiee of the article, and he was inclined to think that the matter must be left very much .to the discretion of the individual analyst.Ur. BARKER, in reply, said that, as Mr. Lloyd had rightly pointed out, to lay134 THE ANALYST. down a satisfactory standard for pure cider was very difficult, if not impossible. At the same time their idea had been that it might be possible to arrive at a fairly satisfactory minimum standard which might serve to reduce the adulteration which had taken place to a considerable extent in the past. From the results which they and other workers had obtained, he believed that, by taking combined account of the various factors available, a fair idea as to the probable purity or otherwise of the article might be obtained.In any case, of course, the standard could only be a minimum standard, and as such it would still admit of a considerable amount of adulteration, but in spite of that it might be useful. They had done a certain amount of work with the object of identifying what might be called “non-apple- juice” ciders, and had devised a test which they thought would show definitely whether apple-juice was present or absent. Of course, as it was the custom in some cider-making districts to use water in making cider, some variation in the amount of apple-juice was to be expected, but the articles to which they had particularly directed their attention in that part of their work contained no apple-juice at all. With regard to boric acid, they had found that a reaction was always obtained with genuine cider, but whether that could be sufficiently extended to determine the presence of a small quantity of apple-juice they were not in a position to say. I t was quite true that the phosphoric acid varied to a relatively large extent, but taken in conjunction with the other factors they thought it would still afford assistance. Mr. CHAPMAN observed that it would be legitimately open to cider makers to make use of yeast foods, which niight themselves contain phosphates. Mr. LLOYD remarked that even in that case the other constituents would not be affected. Mr. L. MYDUELTON NASH aeked whether a small quantity of tannin added to artificial cider would give the reaction which Mr. Barker had described as being capable of detecting the presence of a small proportion of apple-juice, and which he understood was due to the presence of tannins. Mr. BARKER said that the tannin and allied bodies in apple-juice gave a coloration quite distinct from that given by added tannin.

ISSN:0003-2654    

DOI:10.1039/AN909340125b

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

134 THE ANALYST. THE COMPOSITION AND ANALYSIS OF CHOCOLATE. BY NORMAN P. BOOTH, F.I.C., CECIL H. CRIBB, B.Sc., F.I.C., and P. A. ELLIS RICHARDS, F.I.C. (Read at the Neetin.g, March 3, 1909.) THE manufacture of cocoa, chocolate, and the associated products is now an enormous industry, both here and on the Continent, employing many thousands of hands and many millions of capital. The imports of raw cocoa, prepared cocoa, and chocolate into the United Kingdom last year reached the following totals, expressed in pounds : Raw cocoa ... ... ... ... ... . . . 66,981,888 Prepared cocoa and chocolate ... . . . 10,762,772THE ANALYST., 135 The figures for home consumption were : Raw cocoa ... ... ... ... ... . . . 46,411,625 Prepared cocoa and chocolate . . . ... . . . 10,255,238 Cocoa has for many years received a good deal of attention at the hands of the Public Analyst, but cake chocolate intended for eating, as distinct from chocolate powder intended for drinking, has been almost entirely neglected in the administra- tion of the Food and Drugs Acts, and the collective indexes of the ANALYST afford the information that no paper on chocolate as distinguished from cocoa has ever been read before this Society.The industry has of recent years undergone considerable development ; com- petition has become very severe, with the usual result that many inferior products have been put on the market, which the absence of any legal standard has so far allowed to be sold with impunity. The constituent of chocolate upon which the character of the preparation depends is cocoa.The balance of the recipe may be assumed to be sugar, and therefore any variation in the amount of this constituent merely makes the con- fection more or less sweet; but on the cocoa depends the colour, flavour, quality, and cost of the chocolate. I t may be interesting to describe briefly the processes undergone by the cocoa- bean met with in commerce prior to its export from the producing country. As grown the beans are embedded in a saccharine, pulpy mass contained in a thick outer shell or pod. These pods hang from the branches of the cocoa-trees, and differ from the fruits of our Western trees in that the pods are also frequently borne on the main trunk. The trees produce leaves, flowers, and fruit throughout every month of the year, but there are periods of regular harvest, which in the case of the West Indian crop is about the months of May and June, and again in November and December.The colour of the pod is to a large extent a, guide to the planter when the cocoa is ripe for picking. An indication of ripeness is afforded by the contents of the pod separating from the outer shell to such an extent as to give a perceptible sound when the pod is shaken. The ripe pods are cut from the trees and usually opened on the spot with hand-cutlasses. The thick outer covering is useless, and is either burnt or left to decay, and so serve as manure for subsequent crops. The wet, pulpy mass is conveyed to the headquarters of the estate, where the process of fermentation is carried out. Upon this process depends to a, very great extent the success or failure of the quality of the cocoa.The mass is packed into suitable boxes or concrete tanks, to a depth depending upon the practice prevailing in the particular country. Fermenta- tion rapidly sets in, the saccharine matter of the pulp liquefying under these conditions, and the ‘‘ sweatings ” (as this liquid is called) are allowed to drain freely away through perforations provided for the purpose. The temperature rises during the operation, and this is regulated by transferring the mass from one vessel to another at definite intervals, Authorities differ as to the best temperature for the136 THE ANALYST. success of the process, but an outside figure may be stated at GO" C. ; the average is probably nearer 40" to 50' C.The fermentation passes from the alcoholic to the acetic stage, and care has to be exercised that such a point is not reached as to induce a butyric fermentation. The portion of the pulp not passing into the liquid state is converted into a more or less discoloured granular substance, readily removed by washing, or which will rapidly dry on to the beans. The chemical changes which occur in the beans themselves during the fermenta- tion axe very complicated, and it is doubtful if anything very positive is yet known with regard to them; but certainly the modifications in colour, flavour, etc., are such as to alter markedly the character of the beans. The principal loss is in water, and small quantities of the other constituents-proteins, sucrose, starch, etc.-are also lost.The astringent matter of the cocoa is modified, the reduction in the acrid taste bringing about a marked improvement in the flavour. The fermentation being successfully completed, the next step is the washing of the cocoa where this process is adopted, and, where not, the drying stage. To take the washing first. This is only done in the case of certain growths, typical of which is the cocoa p r o d u d in Ceylon. The advantages claimed for this process are the greater degree of freedom from growths and moulds on the sticky residue adhering to the husk from the pulpy matter ; a cleaner product, and one in which the ratio of husk to shell-free cocoa, or cocoa nib, is reduced. Advocates for omitting the washing process state that a certain amount of loss in flavour takes place, that the dry pulpy residue is a, further protection to the kernel, and that the loss by washing is not compensated for by an adequate increase in the market value of the cocoa.Whether washing be resorted to or not, the cocoa must next be thoroughly dried. I n countries such as Trinidad and other parts of the West Indies, where the atmosphere is not usually too humid, this drying operation, or "curing," as it is technically termed, can be done in the open air by the sun's heat. The cocoa is usually spread out on cement or brick-earth floors, covered with matting, earthenware, slate, or other easily cleaned material. Frequently these spaces are provided with an arrangement for running a movable roof over the cocoa if rain should threaten or the night dews be heavy. The cocoa is spread one or two beans deep, and turned over every few hours by means of a rake.In three or four days of good weather the '' curing '' or drying stage is completed, though the operation must not be unduly hurried. In countries where the air is too moist to permit of this being done in the open, or if the crop-time happens in the rainy season, artificial means of drying are being more and more employed, it being imperative to remove the moisture before the growth of moulds can start to a serious extent on the sticky film adhering to the beans. It is not within the scope of this paper to enter into any mechanical details of such apparatus, the only mention which need be lmde is that, in some cases, heated air passes over trays containing the wet cocoa, or suitable vacuum chambers may be used.The moisture percentage is reduced during this drying stage to a low figure, and the dry cocoa obtained is usually less than half the weight of the fermented beans operated on.THE ANALYST. 137 Some cocoas, after drying, are coloured by the use of brick-dust, red earth, or red ochre, to improve the appearance of the integument. This treatment is obviously accompanied by a variable increase in weight, depending on the details of the operation. A certain amount of moisture is absorbed by the finely-divided, dry earth, which also provides a coating of foreign material to assist in the polishing process. In this last operation the seeds are rubbed by hand, by the feet of coolies, or by brushes.Many kinds of cocoa are not treated with foreign matter at all, but when dry are ready for shipment. For manufacture into chocolate the cocoa beans are usually passed through a cleaning machine, or hand-picked, to insure freedom from stones and other forms of foreign matter. They then pass to the important stage of roasting. This is done in various kinds of apparatus, according to the magnitude of the operation in hand, and from a fraction of a hundredweight upwards may be dealt with at a time. I n roasting, the husk of the bean is made friable, and in a condition to be easily removed. Water and acetic acid are expelled, and an aromatic smell and flavour are developed, while the acrid, astringent taste and cheesy fracture of the raw beans are modified materially.The following table illustrates the changes that take place : TABLE I. Grenada 13ean (with shell). Raw. Cunst ituents. Moisture ... ... Fat . . 1 ... Fibre ... ... Total ash . . . Siliceous matter . . . Soluble ash Alkalinity as K,d“ Cold- water extract Nitrogen ... ... ... ... ... ... ... ... ... ... ... ... 6.32 4 6-50 1.96 3.60 2-86 0.10 1.26 0.68 13.50 Roast.. 3.10 46.96 1-86 3.90 3.12 0.12 1.44 0.75 12-90 Trinidad Beau (without shell). Raw. 6.67 54-60 2.28 2.45 2-87 0.03 0.94 0.48 12-73 Roast. 4.45 55.70 2.32 2.48 2.73 0.08 0.95 0.43 12.00 According to the kind of cocoa under operation the roasting must be regulated, it being obvious that a cocoa with a thin shell will burn much more readily than one with a thick shell, which may be further protected by the adhering film of mineral matter in the case of ‘( earthed’’ cocoa.The success of the roasting process depends much on the judgment of the operator in charge, and his experience, enabling him to determine just the right point when the cocoa will give the best results, is a necessary adjunct to the use of thermometers. The roasted cocoa is discharged and cooled as rapidly as possible, for if left lying in a mass, its own heat would probably cause a good portion of the roast to be spoilt. The beans now pass to what is called the (( kibbling” stage, in which the shell is removed. This is done by passing the beans through rollers, so as to crack the138 THE ANALYST. thin shell without damaging the kernel proper. The latter, after the shell is removed, falls into a number of natural segments known as 4bcocoa nibs.” The lighter shell is blown away by an air-blast, while the nibs are collected and graded according to size.There is present also with the nibs small, hard, rod-like particles termed (( germs.” These, although containing liberal amounts of material of food value, are so extremely hard as to necessitate removal in chocolate-making. The value of cocoa depends to a greater extent upon its physical properties, such as colour, taste, and aroma, than on differences in chemical composition. The highest priced cocom are the light-coloured, mild-flavoured ones, typical of which may be mentioned the products of Columbia, Nicaragua, Venezuela, and Ceylon. Of intermediate grade are those of Ecuador, the West Indies, Portuguese West Africa ; and, of the lowest class, cocoa grown on the Gold Coast, though the latter is improving rapidly year by year.The cocoa nibs from the (‘ kibbling ” process are now in a fit condition to pass to the actual chocolate-making operations. The shell-free nib is converted into a pasty condition by grinding on some form of rolls whereby the nib is crushed, and the cocoa butter (which constitutes a large proportion of it) being liberated, the ground product comes away in a soft condition; or the nibs may be broken down to the same stage in what is known as the cocoa mill,” in which granite burr stones revolve upon each other in the horizontal plane. The plastic, or semi-liquid, cocoa mass is then mixed with sugar, and a small quantity of flavouring matter, such as vanilla, cinnamon, etc., and these materials are intimately mixed together in a mdlangew.This machine consists of heavy granite stones mounted on spindles, which revolve on a rotating granite bed provided with a heating device underneath. The butter in the cocoa nibs (which in the case of the best varieties amounts to about 55 to 57 per cent.) causes the whole mass to become plastic. When this has been taken to the desired degree the coarsely-ground product is converted to a fine state by the use of grinding rolls, arranged in series or batteries. Each roll, travel- ling faster than the preceding one, carries on the film of chocolate to the next roll. These rolls are usually made of granite, carefully turned and polished, and capable of accurate adjustment. A steel knife-edge removes the chocolate from the last roll into a pan. The smooth paste may now be brought to the correct temperature for moulding, when it is filled into the moulds, and the latter are chilled as quickly as possible to make the chocolate set with a good colour and appearance, and the operation is completed.The foregoing applies to high-grade chocolates, where the percentage of sugar does not exceed, say, 45 to 50 per cent. If a cheaper quality of chocolate is made, the sugar may amount to 60, or even 70 per cent., though the latter ie an outside figure, At the same time, generally speaking, a poorer quality of nib is employed, which does not contain sufficient natural butter to make the mass workable. To achieve this end an addition of free cocoa butter is made.This cocoa butter is obtained by grinding cocoa nibs, either on such rolls as are employed for chocolatc-making, or in the cocoa mill referred to above. The frictionTHE ANALYST+ 139 in either case is sufficient to melt the butter in the nibs, and cause the mass to be discharged in the form of a cream. This is subjected to hydraulic pressure between some form of filtering media, and the excess of fat is thus expelled. This warm oil, after filtration, forms the cocoa butter of commerce. The pressed cake, after grind- ing and sieving, constitutes the cocoa powder of commerce. I n actual practice it is found to be impossible by this means to reduce the percentage of fat below 11 per cent. Cocoa Husk.-In this by-product, the value of the proteins, and the 2 to 4 per cent.of fat present, are neutralised by the large amount of crude fibre (about 15 per cent.), and its legitimate employment is for use in cattle foods, in which direction some success has already been met with. A certain amount of cocoa butter is extracted from cocoa shell with the aid of solvents, and in Ireland a decoction is prepared from shells, much in the same way as tea infusions are made, this beverage being called “ miserables.” Undoubtedly a large quantity of cocoa shell is finely ground and sieved, and employed under the term cocoa powder,” or, perhaps, “ cocoa-shell powder,” in the lowest grade of so-called “ chocolates ”; but its presence here is quite unjustified unless the purchaser be plainly notified that he is obtaining an article in which at least a portion of the cocoa proper is replaced by the comparatively worthless shell.If the whole bean is employed, the proportion of shell to nib will be about one to eight. The flavourings used in chocolate may be the natural vanilla pod, or the material vanillin (now principally derived from oil of cloves). Cinnamon and its allied flavours are also largely employed. The total quantity of flavouring necessary may be generally stated to be 1 per cent. of the whole at the most, and probably is usually much below this figure. Chocolates of a special type, such as milk chocolate, have come to the front of late years. In milk chocolate a portion of the cocoa is replaced by milk solids. I n the best makes these solids are derived from full-cream milk, and we do not consider it unreasouable to state that, in our opinion, if a chocolate is to be entitled to the term milk chocolate,” and to represent to the purchaser the article he understands by that name, the amount of milk solids present should not be less than 15 per cent.To produce the necessary degree of sweetness from 40 to 45 per cent. of sugar would also be contained in the finished article, and the balance shozdd be derived from the cocoa bean oidy, with a small quantity of flavouring matter. I n the case of nut chocolate, nuts take the place of dry milk solids ; and here again, beyond the necessary amount of sugar, the balance should be supplied by the product of the cocoa bean. As regards the keeping quality of such an article as milk chocolate, there is no need for the use of any form of preservative.The amount of sugar is adequate for this purpose, provided that moisture is eliminated at all stages with every care. The actual process of manufacture of milk chocolate is regarded by each maker as more or less a trade secret, and cannot, therefore, be considered here. Very large quantities of foreign fats are used in making goods of the cheapest140 THE ANALYST. kind, which are sold under the name of chocolate. The principal among these is cocoanut stearine, which may now be obtained with a melting-point very little different from that of genuine cocoa butter, whilst its cost is only a fraction of that of the pure article. From its earliest days the term ‘‘ chocolate ” has always been associated with a confection prepared from the cocoa bean and sugar, with or without flavouring matter; and there is, therefore, good ground for taking strong exception to the introduction of such foreign ingredients as fats other than cocoa butter into manu- factured articles sold under the term ‘‘ chocolate,” without any declaration of their presence being made.It is more a question of fairness to the makers of genuine goods than on the score of health that the presence of these foreign ingredients should be indicated to the purchaser, in precisely the same way that margarine is distinguished from butter. Additions of other foreign material, such as starch other than the natural cocoa starch, have been found in preparations termed ‘( chocolate.” Here the object is solely that of increasing the bulk, or giving the desired light tint without using an excess of sugar in the product; and such an addition is wholly unjustified unless frankly declared.ANALYSIS. The object of the analysis of chocolate, from the point of view of the Public Analyst, is the detection of adulteration, which may assume the following forms, any or all of which may occur in the same sample : (1) Excess of husk, (2) presence of cocoa-butter substitutes, (3) addition of starch, (4) addition of foreign colouring matters. It is obvious that all of the above, with the exception of the last, affect the proportion of real cocoa substance present, but unfortunately no method for the direct estimation of the latter exists, and reliance has to be placed upon various indirect processes.A microscopical examination of the defatted sample will reveal the presence of any added starch, and will afford evidence of the presence of excess of husk. The latter can be recognised by the presence of characteristic spiral vessels and numerous hyaline masses of mucilage, which are tinged rose-pink when treated with ruthenium red and 10 per cent. lead acetate solution. In addition to a microscopical examination of the powder, the analysis of chocolate with a view to the detection and estimation of the above adulterations will comprise the following, though of course in many cases all of these will not be required : (a) Moisture, (b) mineral matter, (c) soluble ash, (d) silica, (e) estimation and examination of the fat, (f) fibre, (9) cold water extract, (h) total nitrogen, (i) an estimation of the foreign starch if found by the microscope, ( k ) the determination of the added sugar.The methods we have adopted are substantially as follows, the portions used for the various determinations being prepared by cutting thin shavings from the cake with a sharp knife. (a) Moisture.-Although the presence of much water is objectionable, and in aTHE ANALYST. 141 properly manufactured sample is impossible, the estimation has comparatively little bearing on the question of adulteration, because the proportion is usually so small ; but it is necessary in order to see that the quantity is not sufficient to seriously affect the other results. As the quantity weighed out may be conveniently employed for the determination of the ash, silica, etc., not less than 5 grams should be taken and dried in a water-oven till constant.(b) Mineral Matter.-The deliberate addition of mineral matter to chocolate is rarely practised, except in the guise of red ochre to highly impoverished specimens. In the absence of foreign additions, the ash figure is of direct value as an indication of the amount of cocoa matter. (c) SoZzLble Ash.-The ratio of ash soluble in water to the total ash is of importance as confirmatory evidence of the presence of ochre or other mineral colouring matter. If the soluble ash is more than half that of the total, it suggests the probable addition of husk or that the cocoa has been treated with alkali. (d) Siliceous Matter.-By this we mean that portion of the ash which is insoluble after evaporation with hydrochloric acid.As the figure obtained in this way, calculated as percentage of the ash, is distinctly greater in the husk than in the nib, the estimation may have considerable value. (e) Estimation am-.? Examination of the Fat.-The actual process employed is of considerable importance, as the complete removal of the fat is attended with some difficulty. Extraction in a fat-free thimble is quite satisfactory, but it is essential that the portion operated upon should be very finely divided by grinding in a warm mortar, and that the extraction should be continued for a long period. Ordinary methylated ether of 0.72 specific gravity, or petroleum ether, may be used as the solvent. Should the extracted portion be required for an estimation of $he sugar, 5 grams may conveniently be taken.For the examination of the fat, a fresh portion of not less than 15 grams of the chocolate should be macerated with petroleum ether in a large stoppered weighing bottle for some hours, after which the solvent is poured off, and the residue extracted twice more with petroleum ether in a similar manner. The fat recovered from the solvent is examined as follows : The refractometer reading at 35" C. (we have used the Zeiss butyro-refractometer) should be taken. Genuine cocoa butter gives a reading closely approximating to 49". As substitutes containing cocoanut oil are perhaps at the present time the coriimonest, the fat should next be examined by the process described by Wauters (ANALYST, 1901, 26, 128 and 292).Since the amount of material at the disposal of the analyst is generally small, 2.5 grams may be used instead of 5. By the figures thus obtained the presence of cocoanut oil is at once indicated, and may be confirmed by a determination of the saponification equivalent and iodine number. Table 11. gives some analytical data in the case of the cocoa-butter substitutes usilally employed. (f) Fzbre.-This is also of considerable value as a means for estimating the proportion of husk. For the determination of the fibre we have used the process described in Allen's In the course of the process it is worth while to observe the tint of the solution Commercial Organic Analysis," vol. iii., part ii., p. 567.142 THE ANALYST.obtained by the acid treatment, as, if it is only faintly coloured red, there is every probability that the amount of cocoa present is extremely small. I TABLE IL-COCOA-BUTTER SUBSTITUTES. Sample. A. B. c. D. E. Cocoanut oil Cacao butter Refract om eter at 35" 0. 40.0 39.0 49.0 50.0 49-0 37.5 49.0 Wauter's Process (5 Grams). Soluble Volatile Acids. Insoluble Volatile Acids. 3.8 11.6 1.8 2-3 1.5 11.4 0.1 4.2 16.8 1 *o 1.8 0.8 15-4 0.4 Saponification Equivalent. 305 220 221 302 287 218 285 Iodine Number - 10.3 10.9 33.7 33.9 32-7 8 to 9 34 to 35 (9) Cold-Water Extract.--As this figure is remarkably constant in the case of cocoa nib, and in chocolate usually ranges from 50 to 70 per cent., it should in every case be ascertained. The process we have adopted is to place 2 grams in a 100 C.C.flask, add 50 or 60 C.C. of water, shake, then make up with water to 100 C.C. The solution is mixed thoroughly, allowed to stand overnight, and, after shaking, 25 C.C. are filtered off, evaporated, and the dry residue weighed. The figure thus obtained represents the sugar present plus the cold-water extract of the cocoa(on the fat-free cocoa approximately 24 per cent.), plus the cold- water extract of the foreign starch, should the chocolate contain any of the latter. (h) Total Nitrogen.-As in unadulterated samples the cocoa is the only nitrogen- containing constituent, the significance of this figure need hardly be pointed out. The Kjeldahl process carried out in the ordinary manner will suffice. (i) Estimation of Foreign Starch.-The proportion of added starch may in most cases be determined by difference and comparison with standard mixtures containing the particular variety of starch employed.If, however, a direct estimation is required, this may be effected by the diastase method, due allowance being made for the starch normally present. This amounts to an average of 17 per cent. for dry and fat-free nib, and 4.5 per cent. for dry and fat-free shell; but owing to the variation in the proportion of natural starch, little is gained in point of accuracy. ( k ) Sugar.-Added sugar may be estimated in a 20 per cent. solution of the sample by the polarimeter, clarifying with lead acetate in the usual way. I t may be mentioned that our experience shows that the cold-water extracts of genuine cocoa nib have such a slight effect on polarised light as to be negligible in a, determination of sugar in chocolate.The average cupric: reducing-power expressed as CuO we find to be about 5 per 100 parts by weight of dry and fat-free cocoa matter.THE ANALYST 143 As we have already pointed out, the one thing in chocolate that cannot be directly estimated is the cocoa, and a correct determination of this is one of the most important objects of the analysis. No satisfactory deductions can be made from the proportions of any single constituent, and the best results will be got by taking into consideration as many data as possible. Of these, the nitrogen, the fibre, the ash, and the fat are the most important. Provided that no nitrogen-containing cereal (such as wheat flour) be present, the nitrogen figure multiplied by 20 will give the proportion of fat-free cocoa matter with an error that will not exceed 2 per cent.Should such a cereal be found, due allowance for the small proportion of nitrogen contained in it aan be made, If by the microscope or otherwise the presence of much sbell is revealed, the factor require8 to be modified accordingly. If the nib has been entirely replaced by cocoa-husk, the nitrogen figure multiplied by 40 will give the proportion of the latter calculated as fat-free husk. Where nib and husk are simultaneously present, it is necessary to obtain some estimate of the amount of the latter. The differences in composition of these substances are shown in the following tables : TABLE 111.-ANALYSIS OF NIB FROM KNOWN SOURCES.Nibs. African ... Grenada ... Guayaquil . . . Trinidad ... Caracas ... Bahis ... Accra ... Ceylon ... Para Puerto Cabello Total Hineral Matter. 2.52 2.60 3.16 2.73 3.24 2.68 3.22 3-81 3.22 3-88 Soluble Mineral Matter. 0.98 1-04 1.32 0.95 1 -58 1.22 1.36 1-66 1-14 1.50 Siliceous Matter. 0.05 0.03 0.04 0.08 0.08 0.05 0.04 0.03 0.06 0.13 4lkalinitg of illinera1 Matter as K20. 0.38 0.55 0.53 0.44 0.74 0.5 1 0.41 0.67 0-45 0.64 Cold- Water Extract. 11-8 9.8 11.4 12.0 9.5 11.4 11.9 12.1 12.6 - Nitrogen. 1.84 2.26 2-32 1-98 2.46 2.44 2-35 - - - Fat. 50.2 50.8 55.7 44.4 50.6 50.2 51.3 - - - Fibre. - 2-94 2.48 - - - 2.87 2-36 3-02 - As it is desirable to obtain the proportion of fat-free cocoa nib and fat-free husk on account of the variable proportions of the fat and of the complications introduced by the possible presence of foreign fat, it is more convenient to calculate the figures on the fat-free substances, and these are shown in the table.It is plain from this that the cold-water extract is, for practical purposes, identical in the husk and the nib, and advantage may be taken of this to effect the purpose at present in view. The cold-water extract of the sample under examination must be corrected for (a) the sugar as ascertained by the polarimeter; and (b) for the extract of any cereal which may be present, though in most cases the latter correction will be very small.144 THE ANALYST4 TABLE IV.-ANALYSIS OF SHELL FROM VARIOUS SOURCES. Nitrogen. Total vlineral Matter. Fat. Soluble Mineral Matter .Nitrogen. Cold- Water Extract. Cold- Water Extract. Mineral Matter. Siliceous Matter. Alksliiiity as Ii,O. Fibrc. Shell. I 12.8 15.7 12.85 13.83 15.8 14.08 - - - Ceylon ... Guayaquil ... African ... Para ... Puerto Cabello A. ... ... B. ... ... c. ... ... D. (raw) ... 6.61 5.63 6.78 8.19 20.89 8.48 11.68 16.28 7.82 4.78 3-53 4.35 5-25 5-24 5.78 4.08 4.62 - 1.0 1-79 0.72 1.45 8-33 0.82 3.34 0.86 - 2-54 2.63 2-80 3.36 1 *13 2.51 2.24 2-12 - 20-7 20.4 18.7 24-6 23.5 19.5 20.3 18.9 244 2.4 2.91 2.13 9.76 2.29 - - - - 3.1 3.5 5.9 5.68 3.31 4-62 - - - TABLE V.-AVERAGE CONSTITUENTS OF NIB AND SHELL. Dry and Fat- free Nib. 1)ry and Fat-free Shell. Factor for )onversion to Nib. Factor for !on versioi I to Shell. Nib. Shell. Moisture ... ... ... Total mineral matter ...Siliceous matter ... ... Fat ... ... ... ... Fibre ... ... ... Nitrogen ... ... ... Cold-water extract ... 3.0 3.07 0.05 50.0 2.8 2.5 11.6 4.5 7-3 1-11 4.4 14-0 2.5 22.0 - 6.14 0.1 5.9 5.05 24.2 - -_ 7-84 1.2 16.5 23.6 - 2.54 Table VI. gives a few data in respect of those flours found in adulterated chocolates. TABLE VI.-FLOURS FREQUENTLY FOUND IN ADULTERATED CHOCOLATES. Flour. Wheat ... ... ... ... Barley ... ... ... Maize (cornflour) ... .-. ... Sago ... Rice.. . L.. ... ... ... Arrowroot . , . ... ... ... ... ... ... 7.7 5.1 0.8 0.9 1.98 0.4 1.97 1.2 0.14 1.23 0.03 0.13 0.5 0.9 0.4 0.5 0.14 0.3 The residual figures, multiplied by J;;, will give the dry fat-free cocoa matter If this agrees with that obtained by multiplying the corrected nitrogen by present.THE ANALYST.145 30'1 49'4 1.05 20 (the factor for fat-free nib), then no shell is present. the following formula may be used to calculate the respective proportions : Let x = the percentage of fat-free cocoa matter (found as above), and y = the percentage of fat-free nib, and N = total nitrogen due to cocoa matter. If it does not agree, then . Then y=40 N -x. The result thus obtained can be confirmed by the proportions of fibre and of ash. TABLE VII:-ANALYSES OF CHOCOLATES (OTHER THAN MILK). (All Free from Fos*e'p Stai*ch and Foreign Fat.) 28.3 50 9 1.04 1. I 2. Mineral Matter. 4 Fat. 1.04 1.01 1.03 1.96::: 2-13 0.85 0.88 1.05 2.75 25.9 23.0 23.3 30.7 32-93.. 29.8 27.2 24.35 0.86 Constituents. 3 . Fat ... Kitrogen ... Xf iiieral matter .. Cold - water estract .. . Sugar ... 'Li-98 51.2 0.98 - I -1 - 17. 18. 19. 20. 21. 22. 23. 24. Coiistitueiits. I 14. I 15. I 16. Average. Vat ... Sugar ... Xitrogen ... Mineral matter ,.. Cold - water extract . . . 28'1 62.2 1-14 1.5 58.2 22-3 61 '4 0.54 - - 22.1 60-0 0 56 _- - 22.0 54.3 0.83 - - 23 *1 59.5 0.85 - - 23.5 56.0 0.75 - - 31.2 52.0 0.87 1-14 5.5.5 30.6 49'1 1-18 - __ 27.4 53.4 0.93 1 '32 56.8 23'7 54.0 1.05 1.48 58.9 23.1 58.0 - ~ 1.34 62.6 TABLE VIII.-ADULTERATED CHOCOLATES AND COCOAS. I I Fihe Calcnlated In Fat-free Cocoa Matter). Character of S tarcli . Fat-free Cocoa Matter. Foreign S tarcli. Sa1nple. Moisture Hugar. Chocolate 1 P P 2 9 9 3 $ 9 4 I 9 5 ? I 6 $ 9 7 9 ) 8 Cocoa 1 ... 1.8 0.8 1.1 1.2 3.03 1.2 3.8 3.6 2.4 48 56 56 44 46 47 40 38 - 15 8 7.5 20 Nil 10 20 30 - 10.0 12.0 12.2 8 3 20.6 12.0 8.4 31 - 8-7 10.0 9.8 16.6 4-5 8.5 10.0 8-8 10.9 Arrowroot Wheat Maize Arrowroot Sago 9 , - 9 9 9 9 * High ash due to addition of red ochw.t Mainly foreign fat.146 THE ANALYST. Table VII. shows the composition of many well-known brands of genuine chocolate now on the market, whilst Table VIII. gives some examples of adulterated chocolate that we have recently examined. MILK CHOCOLATE. In the case of milk chocolate the presence of the milk considerably complicates matters by increasing the nitrogen and introducing a fresh variety of sugar and also of fat. As no other reducing sugar is likely to be used for making chocolate, the presence of milk can at once be inferred from the reducing power of the cold-water extract. Allowance must, of course, be made for the reduction due to the cold-water extract of genuine cocoa ; after which, the residual figure for copper oxide, multiplied by 1.13, will give a fair approximation to the non-fatty solids of the milk, and from this again the protein, and hence the nitrogen, of the milk can be calculated.I n actual practice it is convenient to calculate the nitrogen belonging to the milk directly from the corrected reducing power by multiplying the weight of copper oxide by the factor 0.0672. From this the nitrogen belonging to the true cocoa present can be deduced, and the cocoa, calculated as already described. The milk fat will vary widely in amount according to whether whole or partially skimmed milk has been US^. TABLE IX.-ANALYSES OF MILK CHOCOLATES.English. Constituents. 8. 3. 5. 8. Average. 6. 35.2 4 9 30.5 8.9 41-2 nil nil - 4. 23.7 2.7 21'0 6.5 52.6 nil nil - Total fat ... Made up of- Milk fat ... Cocoa bittter Nilk sugar . . . Cane or beet sugar Foreign starch Cocoa shell . , , Nitrogen ... 32 *7 2.6 30.1 3.8 46.5 nil nil - 36-0 6-4 29.6 8.2 38 '0 nil nil - 27.0 4 % 22-4 7'3 32 -4 nil nil - 29.55 8.2 21.35 10.0 44'4 nil nil - 35.7 8'3 27-4 11.1 39.1 nil nil 1.1 34.6 33.3 31.8 5.6 26.3 8'04 43'2 - - 1-18 3.0 31.6 5.0 54.3 nil nil 0.76 7.6 25.; 10.4 38.4 nil nil 1 *68 Swiss, German, Austrian, and Belgian. I Cons titucn ts. 2. 3. 4. 5 . 6. 9. 10. Average. 7. 8. Total fat ... .. Milk fat ... .. Cocoa butter ,. Milk sugar ... .. Cane or beet sugar .. Foreign starch .. Cocoa sliell .. . .. Nitrogen ..... Made up of- 31 '5 7.7 23.8 7.5 36-1 nil nil - 29-9 6'6, 23.3 10.0 45'6 nil nil - 30'0 8.8 21 *2 11'0 42'2 nil nil - 30.8 5.8 25.0 5.2 35.0 nil nil - 29'5 7.9 21.6 10.8 52.7 nil nil - 29.2 13% 15% 8 '4 36.2 nil nil - 31 -5 8-1 23 -4 9'0 42.7 nil nil 1 -28 33'4 5.7 27.7 7.5 42.9 nil nil 1 *30 30.9 8.4 22.5 5.5 50.2 nil nil 1'1 31 '3 8 *3 23 -0 7.7 42-2 nil nil - 30 TY 8 *1 22.7 8 '26 42.6 - - 1 *24 ITHE ANALYST, 147 In the absence of cocoa-butter substitutes containing the glycerides of volatile fatty acids, the Reichert process will give the amount of milk fat with reasonable accuracy. Table IX. gives the composition of various brands of milk chocolate that we have recently had an opportunity of examining. In some other countries definitions and standards for chocolate have been adopted, and the following list contains all those that up to the present we have been able to discover: The United States Department of Agriculture defines chocolate as it the solid or plastic mass obtained by grinding cocoa nibs without the removal of fat or other constituents except the germ, and contains not more than- 3 per cent.of ash insoluble in water, 3.5 per cent. of crude fibre, 9 per cent. of starch, and not less than 45 per cent. of cocoa fat." Sweet Chocolate is defined 8s "chocolate mixed with sugar (sucrose), with or without the addition of cocoa-butter, spices, or other flavouring materials, and cortains in the sugar- and fat-free residue no higher percentage of either ash, fibre, or starch than is found in the sugar- and fat-free residue of chocolate." Board of PubliC Health of Victoria-DeJinition.--" Chocolate or sweet cocoa mass or confectioner's chocolate or chocolate coating is cocoa mixed with sugar, with or without the addition or subtraction of cocoa fat, and with or without the addition of spices or other flavouring substances." Stadard.--" It shall contain in the sugar- and fat-free residue no higher pro- portion of starch, fibre, or ash than is found in the fat-free residue of standard cocoa+ mass, which itself is defined as containing 72ot more than- 3 per cent. of ash insoluble in water, 4.5 per cent. of total ash, 3.4 per cent. of crude fibre, 12 per cent. of starch (cocoa-starch), and 1Lot less than 45 per cent. of cocoa fat. Union of German Chocolate ~anufactu~ers-DeJinitioia.-" A mixture of roasted and shelled cacao with sugar (beetroot-sugar), and an addition eventually of cacao- butter, vanilla, cinnamon, cloves, or other spices or essential oils." Swiss Society of Analytical C?zemists.-Definitions have been drawn up which will probably be rendered official. Chocolate is described as '' a mixture of cacao with sugar, either sold moulded or powdered." Amount of sugar varies from 40 to 70 per cent.No other ingredients admitted except spices (vanilla, benzoin, Tolu or Peruvian balsams, cinnamon, cloves, nutmeg). Fat and sugar together should not exceed 80 to 85 per cent., and the remainder should consist of fat-free cocoa mass. Ash not to be above 3.5 per cent. Belgium and Roumania are the only two States with official regulations as to composition.Belgium insists on the presence of at least 35 per cent. of shelled cocoa, other- wise the word '( chocolate '' must be excluded.148 THE ANALYST. Roumania requires that chocolate must be made from cocoa beans and sugar only. The Austrian Codex describes chocolate as a uniform mixture of cocoa mass and white sugar in the proportion of 40 to 50 per cent. of the former and 50 to 60 per cent. of the latter, with a small amount of harmless aromatic substances. DISCUSSION. Mr. BODMER said that at present it seemed to be agreed that articles sold as ‘‘ chocolate ” or ‘( chocolate powder ” might legitimately contain added starch and other ingredients besides cocoa. Hassall evidently held this view, stating that sugar and starch are used, and that in the better varieties of chocolate Maranta arrowroot is employed. Mr. C. J. WATERFALL asked if the authors knew of any means of distinguishing the inner fibre from the outer husk, and whether there was not some recognised standard among chocolate-makers as to the percentage of fibre. He presumed that the presence of most cocoa-butter substitutes would be indicated by the iodine numbor. Mr. E. R. BOLTON said that a simple method was to estimate the starch by the diastatic method. The discrepancy bet ween diastatic and acid hydrolysis was greater in the case of husk than in the case of cocoa itself. The PRESIDENT said that he had difficulty in understanding how cocoa could have so high a nutritive value as was commonly supposed. The percentages of fat and nitrogen, of course, were large, but the quantity of the article consumed in a, given time was so small that this must be of comparatively small importance. Nr. BOOTH, in reply, said that the articles containing added starch to which Mr. Bodmer had referred were for the preparation of beverages, whereas in this paper they dealt exclusively with chocolate for eating. He had never heard that English manufacturers had any standard for the proportion of husk in chocolate. With regard to nutritive value, the point of difference was that in the case of coffee the infusion only was consumed, whereas in the case of cocoa the matters in suspension were included. +I+**+€+*

ISSN:0003-2654    

DOI:10.1039/AN9093400134

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

148 THE ANALYST. NOTE ON THE DETERMINATION OF PETROLEUM IN TURPENTINE. BY J. H. COSTE, F.I.C. (Read at the Meeting, March 3, 1909.) THE author, in a paper published in this journal (1908, 33, 219) on the examination of turpentine and turpentine substitutes, stated that ‘‘ For the direct determination and separation of petroleum spirit in turpentine” he was “of opinion that the process of polymerisation and sulphonation proposed by Armstrong (Journ. Soc. Chem. Ind., 1882, 1, 480) is in every way preferable to the various drastic and even pyrotechnic processes suggested by later workers.”THE ANALYST, 149 In the ANALYST for November, 1908 (p. 433), appeared an abstract of a paper in the Oil and Colozcr Trades' Jozmzcd (August 15,1908,503-506), by A. K. Turner, in which it is stated that "The results thus (by Armstrong's method) obtained are invariably very low-at times as low as 20 per cent.below truth." The writer then adduces experiments with mixtures of kerosene (!) and turpentine, in which the amount of unpolymerised steam distillate is certainly considerably less than the amount of kerosene present in the mixture. Apart from the fact that the experimental details differ materially from those described by Armstrong, the distinction made by that author between petroleum oil and petroleum spirit has been neglected. Armstrong, after stating that an exact distinction is difficult, adopts for the purposes of his paper the term " petroleum spirit " for the portion of petroleum distilling in steam at the ordinary pressure, and "petroleum oil" for the portion which is not so distillable.Kerosene, an unusual adulterant, and one which is easily detectable by fractional distillation, is a mixture of substances, only some of which can be distilled in steam. A sample examined in this laboratory flashing above 100' F. (Abel test) 15.5" 15.5" D-- C. 0.7980, nD200 1.4434, and distilling from 150" C. to above 250' C., was distilled with steam. In one and a half hours 58.5 per cent. by volume had distilled, and only traces were then coming over. The distillate had the following properties: D-----, C. 0.7803, n,20° 1.4332, and when treated with sulphuric acid in the manner 15-5O 15.5 described by Armstrong, lost only 5.2 per cent. of its volume-ie., was reduced to 55.5 C.C. The apparently considerable loss observed by Turner (loc.cit.) was due to the fact that the portion not volatile in steam was not measured by him; a pre- liminary steam distillation would have separated his mixture into petroleum oil, with traces of resinous matter and petroleum spirit, and turpentine. I t is the petroleum spirit alone that the polymerisation method is intended to detect and estimate. The above experiment shows that this can be done with some accuracy, or at least that the diluted acids recommended by Arinstrong have but little action on American petroleum. Armstrong states that shale oil is so much attacked by sulphuric acid that the method is not applicable. Turner evidently realises the cause of his low results, but is apparently not aware of Armstrong's distinction between petroleum oil and spirit, The process adopted by Turner of shaking with concentrated sulphuric acid and measuring the separated top layer, which he calls petroleum, is more violent than Armstrong's.I t may, as he states, yield results which approximate to the amount of petroleum added-in fact, it appears to do so-but these results are only due to a happy compensation of errors. A pure turpentine treated by this process gave no distinct top layer, but was con- verted into a dark viscous homogeneous mass. To some of the same turpentine a petroleum spirit having a refractive index at 20' of 1.4475 was added in the proportion of 20 C.C. in 100 C.C. of mixture. One hundred C.C. treated as described by Mr. Turner gave 23 C.C. of a colourless top layer having a refractive index 1.4763, and an odour of cymene.This was reduced by subsequent treatment to 19.5 c.c., the refractive index being lowered to 1.4736.150 THE ANALYST. Treatment with Nordhausen acid reduced the refractive index to 1.4642, which is still much higher than that of the petroleum added. I n another experiment a mixture was taken containing 80 per cent. by volume 15.5" 15 5" of turpentine (nD200 1.4708, D-.- C. 0.8703) and 20 per cent. of petroleum spirit::: 15.5" 15.5" (nD2O9 1.4421, D- C. 0.8000). This finally yielded 18 per cent. by volume of a liquor having an odour like that of cymene and ?zDyoo 1.4798, Dtgo C. 0.8775. The liquid separated shows a great tendency to form an emulsion during the washing with water, which is somewhat inconvenient.I t is clearly not all petroleum, as is shown by its physical properties. Cymene (@j'7° 1.4926, D E C. 0.8728) and 15.5" 15.5" 15.5" terpinene (q, 1.4845, D- C. 0.849) are known to be formed by the action of sul- phuric acid on turpentine. It appears highly probable that the liquor separated is principally one or other of these or a mixture. Armstrong states that cymene is normally present with the most careful working in the final result of polymerisation by his method. I t would appear that the use of a considerably greater volume of strong acid leads to the formation of much more cymene.-I When it is considered that the action of strong sulphuric acid on turpentine is very complex, including as it does isomerisation, polymerisation, sulphonation, and charring, with the evolution of some SO,, it is hardly to be expected that a product separating out by reason of its relatively low specific gravity and solubility should accurately represent the unattacked amount of an adulterant or addition.I t is conceivable that if all the turpentine and its products were charred or sulphonated, the unaltered residue would represent the petroleum present in a mixture. It should be stated that Armstrong's method yields, in the case of adulterated samples, liquids of low specific gravity which are evidently petroleum. In conclusion, the author still maintains that Armstrong's method, based as it is on sound scientific principles, is capable of giving excellent results, if properly used- that is, if the petroleum oil be determined by distillation of the original sample in a current of steam, and petroleum spirit by polymerisation of either the distillate from this process or another portion of the original.He fully realises the ease with which a misapprehension as to Armstrong's original statements might arise on the part of a worker deprived of access to the actual paper, and obliged to rely on second-hand textbook statements, and is solely concerned to maintain the accuracy of his previous statement. * Eighty-five per cent. of this was unattaclkd by sulpliuric acid iii the cold. It is admittedly remarkable that no cymene separates f'rom pire turpentine when treated witli sulphuric acid. The author suggests two possible reasons: (1) that in such a case it is sulphoiiated, whereas in thc prcsencc of petroleum it is dissolved in this substance and separated from intimate contact with the acid ; (2) that its disappearance, and possibly the disappearance of petroleum in adulteratcd samples, is dnc to tlie formation of enmlsions, or to its solution in the polymerides formed.THE ANALYST.151 The experimental work in connection with this subject has been carried out by Mr. R. Parsons, of this Department, to whom the author’s thanks are due. CHEMICAL DEPAHTMENT, L~NIWN COUSTP COUNCIL. DISCUSSION. Mr. L. MYDDELTON NASH said that since Mr. Coste’s previous paper he had made further experiments with the simple shaking test which he had then showed to be capable of detecting petroleum spirit in turpentine, and had found it possible to obtain fairly good quantitative results with it.A marked tube filled to the mark with the turpentine under examination was shaken, and the resulting froth compared with that produced by mixtures of known composition in standard tubes marked at the same height and with the same air space above the liquid. The amount of frothing was in direct proportion to the petroleum spirit present, turpentine giving no froth, but only large air bubbles, which broke immediately. A series of mixtures had been prepared for him which he had tested in this way with the following results : Found. 25 10 50 5 10 20 10 75 Present. 25 10 50 5 15 10 10 80 Found. 50 10 5 20 25 10 35 35 Present. 50 10 10 20 15 10 25 25 The PRESIDENT asked whether other spirits, such as rosin spirit, would be shown by the test Mr. Nash had described, or would interfere with it. Mr. NASH said that he had not tried the test with rosin spirit, as he felt certain it would be of no use, but only with petroleum spirit, not petroleum oil. He did not think that rosin spirit was now being used to adulterate turpentine. The petroleum spirit which he took for his tests was that which was being used in large quantities by manufacturers as a substitute for turpentine. Mr. COSTE, in reply, said that it was remarkable that the shaking test mentioned by Mr. Nash should give results so near the truth. The direct treatment with strong sulphuric acid appeared to give results fairly near to the truth, although it was based on entirely incorrect premisses. I t was, he believed, originally due to Herzfeld. For purposes of accurate determination he had found Armstrong’s method to be a really good one. During recent years in London he had met with very little adultera- tion with petroleurn, but he gathered that in the North of England this form of adulteration was still common.

ISSN:0003-2654    

DOI:10.1039/AN9093400148

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

152 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. Methods for Distinguishing Atoxyl [Sodium p-Aminophenylarsenate] from Arsacetin [Sodium p-Acetaminophenylarsenate]. A. Labat. (BZLZZ. Soc. Pharm. B o d , 1908, 289; Phnrm. JOUTIZ,., 1909, 82, 60.)-The chief advantages of arsacetin over atoxyl are that it may be sterilised in an autoclave at 130' C. without decomposition, and that it is less toxic. It may be distinguished from atoxyl by a number of reactions, among which are the following : Ten per cent. aqueous solutions are used. On mixing a drop of the atoxyl solution on an object-glass with a drop of a 1 per cent. solution of cobalt nitrate, nickel chloride, manganese sulphate, or magnesium sulphate, there is obtained a crop of small crystals, sometimes resembling those of ammonio-magnesium phosphate. In the case of manganese sulphate, a small part of the precipitate is amorphous, but the bulk is crystalline.Arsacetin, on the contrary, gives an amorphous precipitate with cobalt nitrate and manganese sulphate, but none at all with the other reagents. On mixing 1 C.C. of 95 per cent. alcohol and 2 drops of adoxyl solution, a crystalline precipitate is formed, but none with arsacetin. On mixing 1 C.C. of the atoxyl solution with 1 C.C. of 5 per cent. sulphuric acid, there is formed a very light crystalline deposit; with a solution of half the strength there is no reaction, Arsacetin, under these conditions, gives a precipitate 60 dense that a magma is produced. I n both cases the crystals are in the form of hexagonal tables.On adding bromine water, drop by drop, to 1 C.C. of the atoxyl solution, there is formed an amorphous precipitate surmounting a pale yellow liquid. With arsacetin the precipitate formed is deposited in tufts of fine needles, easily observed under slight magnification. When 0.20 gram of arsacetin is heated with 10 C.C. of a mixture of equal parts of alcohol and sulphuric acid, the odour of ethyl acetate is given off; atoxyl gives no such odour. Atoxyl and its Derivatives. F. Blumenthal and E. Jacoby. (Biochenz. Zed., 1909, 16, 20-36.)-The authors have carried out an investigation on the toxicity and action of atoxyl and its derivatives, particular attention being paid to the relative poisonous properties of the latter. The use of these has been suggested from the known curative or antiseptic properties of atoxyl in cases of sleeping sickness and syphilis, and acetyl, mercury, and other compounds of atoxyl have been prepared for this purpose.Acetylatoxyl appears to be less toxic than atoxyl itself, whilst the mercury salt is more so. I t is curious that, whilst sodium p-iodophenylarsenate is considerably more active than atoxyl, mercury p-iodophenylarsenate is less poisonous than either. Atoxyl, when injected into the body, remains principally in the blood ; only traces of arsenic are found in the chief organs, and its action on the organism appears to take place in the blood. AtoxylTHE ANALYST. 153 and its derivatives, mentioned above, eventually pass into the urine, and the urine of patients who have been treated with atoxyl or its derivatives gives a red colora- tion with either a-naphthol or P-naphthylamine, after being diazotised with sodium nitrite and hydrochloric acid (cf.ANALYST, 1908, 33, 477). w. P. s. Composition of Extract of Crab. H. Barschall. (Arbeit. Kuised. Geszwd- heitsnmte, 1909, 30, 74-76.)-A sample of extract of crab examined by the author yielded the following quantities of nitrogen : Total, 7.7 per cent. ; as amino com- pounds, 0-9 per cent. ; as ammonia, 0.15 per cent. ; in phosphotungstic acid precipitate, 2.7 per cent. The small quantity of nitrogenous matter precipitated by phospho- tungstic acid is worthy of note, and the difference between the total amount of nitrogen and the sum of the separate quantities of nitrogen estimated points to the presence of other forms of nitrogen in the extract.Creatine and creatinine were not present in the sample, the author confirming in this respect the statement of Ackermann and Kutscher (ANALYST, 1907, 32, US). w. P. s. Estimation of Water in Cresol Soaps Solutions. W. Spalteholz. (Chem. Zeit., 1909, 33, 181-182.) - Cresol soap solutions (liquor cresoli saponatus) containing not more than 13 per cent. of water, and about 61 per cent., or less, of cresol, are miscible in all proportions with glacial acetic acid, giving a clear solution. If the soap contains more than this amount of water, the addition of acetic acid, drop by drop, causes a turbidity, which only disappears on the addition of an excess of the acid. I n a similar manner, titration of the soap with 50 per cent.acetic acid gives a measure of the amount of water present, if the quantity of acid required to give a turbidity with the sample under examination be compared with that required in the case of soaps of known water-content. w. P. s. Estimation of Fat in Flesh. E. Baur and H. Barsehall. (Arbeit. KuiserZ. GeszLndheitanmte, 1909, 30, 55-62 .)-Of the methods which have been proposed for the estimation of intramuscular fat in flesh, the author considers that the pepsin- digestion method gives the most correct results, and that the results obtained by other methods must be compared with this as a standard. The following process, as will be seen from the appended figures, yields results which compare favourably with those yielded by the digestion method, and is much more rapid.About 2 grams of the flesh, finely minced and free from fat and sinew, are heated in a flask on the water-bath with 20 C.C. sulphuric acid (1 volume of sulphuric acid to 1 volume of water), the mixture is agitated from time to time, and in about thirty minutes the fibrous part of the flesh will have dissolved. The solution is then cooled, extracted with ether; the ethereal solution of the fat is evaporated, and the residue of fat weighed. In the digestion process, 2 grams of the flesh are treated with 100 C.C. of pepsin-hydrochloric acid solution, prepared by dissolving 3 grams of Merck’s pepsin in 500 C.C. of water, and adding 100 C.C. of p hydrochloric acid. The digestion is154 THE ANALYST. carried out at a temperature of 37" C., and about four days are required for the com- plete solution of the flesh.The solution is then extracted with ether in order to obtain the fat. The following quantities of fat were found in the flesh of various animals : Digestion Process. Sulphuric Acid Process. Beef . . . ... ... Beef ... ... ... Pork ... ... ... Pork ... ... ... Mutton ... ... Per Cent. 1.80 3-45 10.30 7-45 4.35 Per Cent. 1.65 3.30 10.45 7-70 4.80 w. P. s. Estimation of Sugar in Flesh. E. Baur. (Arbeit. Kaiserl. Gesundheitsamte, 1909, 30, 63-73.)-The author has adapted the well-known colour reaction which carbohydrates show when treated with strong sulphuric acid and cc-naphthol or resorcinol, for the quantitative estimation of sugars in liquids containing nitrogenous matters.In order to preserve the limits of proportionality, the following procedure should be accurately followed : One C.C. of the liquid to be tested is placed by means of a pipette at the bottom of a test-tube provided with a ground-glass stopper. Nine C.C. of pure sulphuric acid are then run in from a burette, the point of which is allowed to touch the side of the test-tube held in a slanting position. Then 8 to 10 drops of an alcoholic solution of thymol of a concentration of 15 grams per 100 C.C. are added. The test-tube is then closed, and turned quickly over twice in succession, whereby an instantaneous mixing of the contents is effected. The maximum coloration is reached in about half an hour, when the contents of the tube have cooled. The intensity of the coloration is proportional to the concentration of sugar up to a limit of 0.6 per cent.of dextrose. The quantitative measurement is, however, best effected by means of the spectroscope. The coloration shows a sharply characteristic absorp- tion band with a maximum absorption in the green part of the spectrum at h = 506 pp. As the concentration of the colouring matter increases, the band increases in width, chiefly towards the blue end, and only slightly towards the red. I t is necessary to calibrate the instrument by means of standard solutions of dextrose, plotting curves with the scale divisions as abscism and the logarithms of the concentrations as ordinates. The limit of the band is not very definite on the blue side, but is very sharp on the red side, and it is preferable to use the latter for the determinations. I n making observations, the conditions under which the instrument is used must, of course, coincide with those employed for its calibration.I t is true that proteins also give the same colour reaction, which really depends on the production of furfural derivatives, but they react far more feebly than the sugars or carbohydrates (glycogen), and the bulk of the reactive proteins can be separated by boiling and filtering the extract. The error in observing the limit of the absorption band andTHE ANALYST. 155 that involved in establishing the coloration in duplicate are both fairly considerable ; the limits of error amount approximately to 20 per cent. of the absolute concentra- tion, but the cupric reduction methods are not more accurate, owing to the presence of the nitrogenous extractives.At concentrations of 0.3 per cent. downwards, the spectroscopic method is indeed the most accurate and convenient. The author gives illustrations of its application to the analysis of urine and flesh. J. F. B. The Quantity of Phosphorus and Iron in Various Vegetables. E. Haen- sel. (Biochem. Zeit., 1909, 16, 9-19.)-The following percentage amounts of water, ash, phosphoric acid, and ferric oxide were yielded by vegetable foods examined by the author. In each case the figures given for ash, phosphoric acid, and ferric oxide, are the mean of two estimations. Endive ... ... Lettuce ... ... French beans.. . ... Winter cabbage ... Spinach ... Celery (head) ... (leaves) ...Red cabbage ... ... Carrot 8 ... Radish ... ... Tomatoes ... ... Onions ... ... Beetroot ... ... Potatoes (Magnum bonunz; Mushrooms . . . ... Bananas ... ... Kohlrabi (headj ... Wkte cabbage ... Curled cabbage' ... ,, (leaves) ... ? * (red) ... Apples ... ... Figs (dried) ... ... Water. 92-03 91.91 83.10 86.25 91.93 87-24 81.56 86.59 85.28 92.1 2 90.55 86.84 86.72 86.33 93.10 85.82 82.85 79-60 78.30 85.90 81.62 74-78 18.24 Ash. 0.968 1.288 1.605 0.887 1.655 0.907 1.901 0.986 1.875 0.553 0.610 0.757 0.762 0.947 0.408 0-477 0.864 0.762 1.068 0.788 0.177 0.310 2.322 Phosphoric Acid. 0.101 0.127 0.204 0.146 0.135 0.136 0.190 0.223 0.172 0-067 0.065 0-100 0.137 0.106 0.057 0.106 0.150 0.096 0.162 0.143 0-018 0.035 0-104 Ferric Oxide. 0.0320 0.0550 0.0560 0.0140 0.0360 0.0060 0.0700 0.0170 0.0390 0.0030 0.0020 0.0130 0*0030 0.0040 0.0006 0*0030 0~0080 0.0200 0.0110 0~0010 0-0007 0*0003 0.0360 The phosphoric acid was estimated by incinerating the sample, extracting the ssh with dilute nitric acid, precipitating the phosphoric acid with molybdate, con- verting the precipitate into ammonium magnesium phosphate, and weighing as magnesium pyrophosphate.The iron was separated from a nitric acid solution of the ash as the basic salt in the usual way and weighed as ferric oxide. w. P. s.156 THE ANALYST, Detection of Benzoie and Salicylic Acids in Fermented Beverages and Milk. L. Robin. (Aim. Chim. unaE., 1909, 14, 53-54.)-The test previously described for benzoic acid (ANALYST, 1908, 33, 420), depending on its conversion into nz-dinitrobenzoic acid and thence into ammonium m-diaminobenzoate, is available for its detection in wine, beer, cider, and milk.The test for salicylic acid may also be made at the same time. In the case of fermented liquids, 50 to 60 C.C. are treated with a little ferric chloride and hydrochloric or sulphuric acid, and shaken with 40 to 50 C.C. of ether. After washing the ether once or twice, it is divided into two portions, and one half is taken for the salicylic acid test. The other portion is shaken with 25 C.C. of an alcoholic solution of sodium bicarbonate; the alkaline solution is placed in a capsule and evaporated on the water-bath, the residue being treated as directed loc. cit. I n the case of milk, the casein and the fat &re first removed in the following manner: Ten C.C.of a 5 per cent. solution of sulphuric acid and 20 C.C. of 95 per cent. alcohol are placed in a beaker, and 50 C.C. of the milk are poured in in a fine stream, whilst the contents of the beaker are rotated. After standing for four or five minutes, the coagulated milk is placed on a filter, and the filtrate returned until it comes through clear. The filtrate is then placed in a separating funnel with 50 C.C. of ether. In order to avoid emulsification, the separating funnel should be completely filled by the addition of water, and the extraction is effected by reversing the funnel several times. The ethereal extra,ct is washed with water containing a little alcohol, and is then divided and tested for benzoic and salicylic acids in the manner described above.Under these conditions it is possible to detect the presence of 1 mgm. of benzoic acid. J. F. B. Detection of Saccharin in Beer. G. Jorgensen. ( A m . Falsif., 1909, 12, 58-59.)-The following method is proposed, its chief feature being the elimination of salicylic acid and bitter principles which interfere with the identification of saccharin. Five hundred C.C. of the beer are evaporated on a water-bath to the consistency of a syrup, and the residue is well stirred with a quantity of 96 per cent. alcohol. After decanting the alcoholic solution, the solid residue is moistened with water and again extracted with alcohol, and the united extracts are evaporated until the alcohol has been expelled. The aqueous syrup thus obtained is acidified with a few drops of sulphuric acid, filtered, and the filtrate is shaken out with several successive portions of ether. The ethereal solution is evaporated, the residue is taken up with a little water, a small quantity of dilute sulphuric acid is added, and saturated potassium permanganate solution is added, drop by drop, until a permanent pink coloration is obtained.Saturated oxalic acid solution is then added to reduce the precipitated manganese dioxide, an excess of oxalic acid being avoided ; and, after filtration, the colourless solution is extracted with a mixture of ether and petroleum spirit, On evaporating the ethereal extract a crystalline residue, possessing an extremely sweet taste, is obtained should the beer contain saccharin. The treatment with permanganate will have removed any salicylic acid present in the beer, and the saccharin obtained may be further identified by converting it into salicylic acid, and applying the usual tests for the latter substance.(Cf. ANALYST, w. P. s. 1905, 30, 21, 205.)THE ANALYST. 157 Comparative Analyses of Different Spirits Distilled in Air and under Reduced Pressure. C. Girard and Chauvin. (Mon. Scientif., 1909 [IV.], 23, 73-89.)-The amounts of alcohol estimated by distillation in the air and under reduced pressure were the same. In the former case the sum of the acidity of the distillate and residue was invariably greater than the total original acidity, whereas with distillation under reduced pressure the amount was the same as before. Distillation in the air invariably gave a greater amount of aldehydes, but the quantity of furfural was the same in each case.The amount of esters found in cognac and marc brandy was greater by distillation in the air than under reduced pressure, whereas with rums and Kirsch liqueurs the reverse was the case. The increase of esters in the Kirsch was attended by a corresponding decrease in the hydrocyanic acid. No differences were obtained by the two methods of distillation in the proportion of higher alcohols. Several analyses of one and the same spirit gave concordant results. In the authors’ opinion distillation under reduced pressure, being more regular and preventing the action of air, gives more exact results than the usual method of distillation. C. A. M. On the Methods of Examining Vinegar.J. Brode and W. Lange. (Brbeit. KaiserZ. Gesundheitsanzte, 1909, 30, 1-54.)-The acetic acid in vinegar may be accurately estimated by the use of phenolphthalein as indicator after sufficient dilution of the sample. The results obtained without dilution by “spotting” on litmus paper were found to be about 1 per cent. lower in terms of $ alkali solution. Litmus, therefore, cannot be recommended as the universal indicator for vinegar as suggested by Farnsteiner. For the detection and estimation of mineral acids the method of Schidrowitz (ANALYST, 1903, 28, 233) gives excellent results. Even in the case of highly coloured vinegars an addition of a trace of mineral acid may be detected by applying the method as a ‘ I spotting ” test on methyl orange paper.For the estimation of glycerin the iodide method of Zeisel and Fanto (Zeit. anal. Chem., 1903, 42, 575), carried out in the same way as for wine, on the residue left on evaporation of the vinegar has proved very satisfactory. Estimations of the total solids in vinegar showed that a certain proportion of acetic acid is obstinately retained by the residue, and that to obtain accurate results this acid should be subsequently titrated. Thus, in a commercial wine vinegar the residue amounted to 0.79 per cent., and contained 0.2 per cent. of acetic acid. When the dish was continually shaken during the evaporation, the residue from the same vinegar was 0.64 per cent., and contained 0.08 per cent. of acetic acid. I n estimating oxalic acid the best method is to neutralise the vinegar and to precipitate the oxalic acid as calciuni oxalate, which, after purification by repeated reprecipitation in the presence of an excess of calcium, is finally titrated with potassium parman- ganate solution.The detection of heavy metals (lead, copper, tin, zinc) is difficult in the case of highly coloured vinegars. The following method is therefore recommended: One C.C. of concentrated hydrochloric acid is added to 10 C.C. of the boiling vinegar, and the liquid treated little by little with potassium chlorate (0.1 to 0.15 gram) until of a pale yellow colour, after which it is boiled for a, minute, treated with sodium acetate (to remove free hydrochloric acid), and158 THE ANALYST. subjected to a current of hydrogen sulphide. In this way it was found possible to detect as little as 16 mgm.of lead, 21 mgm. of copper or zinc, and 30 mgm. of tin in a litre of wine vinegar. Salicylic acid may be quantitatively extracted from vinegar by adding a few drops of sulphuric acid to the sample, and shaking it with an equal volume of ether. The ethereal extract is washed twice with water con- taining sulphuric acid, then mixed with a little water and evaporated on the water- bath, and the salicylic acid in the aqueous residue estimated colorimetrically. Beizxoic acid is readily detected by Leach’s method. The residue from the ethereal extract of the vinegar is heated over a small flame on a watch glass covered by another clock glass, whilst a diaphragm of filter paper is fixed between the two. The benzoic acid passes through the, paper and sublimes on the upper glass, whilst volatile impurities are retained by the paper.The crystals may be recognised by their form and behaviour towards ferric chloride solution. One mgm. of benzoic acid could thus be detected with certainty in 100 C.C. of wine vinegar, but not with certainty in malt vinegar. C. A. M. Detection of Yohimbi Bark in Pregarations. C. Griebel. @it. Untw- swh. Nahr. Genussm., 1909, 1’7, 74-78.)-The presence of Yohimbi bark (Coiynnnthe Yolzimbe of the Cameroons) may be detected in powdered drugs, etc., by means of the microscope and chemical tests. Microscopically, the bark is characterised by the presence of large, but narrow, bast fibres, which are frae from pores, and schlerenchy- matous cells are entirely absent. Compressed, porous cork cells are present, and are generally free from pigment. The cells of the parenchymatous tissue have brown walls, are almost free from starch, but exhibit masses of red-brown particles. The chemical tests depend on the colour-reactions given by yohimbine, one of the alkaloids present in the bark. This alkaloid may be obtained by extracting an alkaline solution of the drug with ether. The other alkaloids are also extracted, but their presence does not interfere with the reactions. The tests are applied to the dry residue obtained on evaporating the ethereal solution. When treated with concentrated sulphuric acid, yohimbine gives no coloration, but the addition of a, small crystal of potassium bichromate causes the appearance of a streak with blue- violet edges. This coloration changes to bluish-grey and then to greenish-brown. Concentrated nitric acid gives an intense yellow coloration. With Erdmann’s reagent a dark grey-blue colour is obtained, which changes to yellowish-green, whilst Friihde’s reagent gives a grey-blue colour, changing almost at once to dark blue, and then green. Mandelin’s reagent (1 part of vanadate to 200 parts of sulphuric acid) yields a dark blue coloration, whilst the reagent itself becomes orange in colour, and finally red. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9093400152

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

158 THE ANALYST. BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. A Physico-Chemical Method for Comparing the Antiseptic Value of Disinfectants. S. B. Schryver and R. Lessing. (Jounz. SOC. Chenz. I?zd., 1909, 28, 60-65.)-The authors propose to measure, by means of the alteration of electro- lytic conductivity of the liquid, the rate of chemical change produced in a, protein-THE ANALYST. 159 containing mixture infected with bacteria, and to observe the variations in this rate of chemical change in the presence of certain concentrations of disinfectants, as compared with a standard phenol. The medium used is either gelatin-peptone or sodium caseinogenate-peptone mixture containing about 5 per cent. of gelatin or sodium - - caseinogenate (Le., caseinogen dissolved in the requisite amount of sodium hydroxide) and 1 per cent.of Witte's peptone. In all cases a mixed infection from faxes is employed, as this was found to produce a more rapid change than a pure strain inoculation. The ordinary method, as usually described, was used for deter- mining the electrolytic conductivity, the electrodes of the apparatus employed being shown in the accompanying figure. These elec- trodes consist of platinum plates made of fairly stiff pieces of metal 10 mm. square and placed 20 mm. apart, and coated with platinum-black. These were fused into the glass tubes here figured, the tubes being filled with mercury, into which the wires connecting the electrodes with the remainder of the apparatus were placed. The tubes were fitted by means of rubber into a glass collar which rested on the rim of the outer tube, and enabled the position of the electrodes to be conveniently adjusted.The electrodes thus constructed can be used in many determinations, and readily moved from one test-tube to another. These test- tubes were 30 by 95 mm., and were kept with their contents in a bath at 37" C., at which temperature all the determinations 7 were made. A single coil of about 100 ohms serves as a counterbalancing resistance. Previous investigations have shown that the curves representing (1) the con- ductivity of the caseinogen solution in different stages of digestion, and (2) the nitrogen in the filtrate from the tannic acid precipitate, were very similar in form. In the following experiment the results given in the table below were obtained: A sterile solution of 5 grams of gelatin and 1 gram of peptone in 100 C.C. of liquid was infected with faxes and incubated at 3'7' C.During the early period of incuba- tion the liquid was thoroughly shaken up to insure uniform infection of the liquid. At the commencement of incubation, and at intervals of twenty-four hours, 10 C.C. of the mixture was weighed out, diluted to 100 c.c., and 40 C.C. of tannic acid mixtiire added, the solution further diluted to 200 C.C. and filtered, and the nitrogen determined in 150 C.C. of the filtrate. Time of Incubation. Beginning ... 1 day ... ... 2 days ... ... 3 * I 4 1 9 6 ? ) ... ... ... ... ... ... Nitrogen in Filtrate (Milligrams). 11.3 13.0 19.3 43.9 56.0 89.3 Resistance in Ohms. 156.6 125.7 55.0 39.0 30.0 18.3 Conductivity in Gemnihos.6.39 7-96 18 -18 25.64 33.33 56.64160 THE ANALYST. When an experiment with varying amounts of a disinfectant is to be made, tho infected gelatin and peptone liquid, warmed and well mixed at 37" C., is placed in six sterile flasks, 90 C.C. in each, to which are added 10, 5, 2, 1, and 0.5 C.C. of a 5 per cent. solution of standardised phenol; the remaining flask has no disinfectant added. The liquid in each case is made up to 100 C.C. with sterile water. Quantities of 15 C.C. of the liquid from each are taken out at intervals, and the conductivity determined. Time must be allowed for the electrodes to attain the temperature of the liquid (37" C.). The retarding effect of the smaller quantities of disinfectant is well shown in the results, while total inhibition is shown in the case of the larger amounts.This communication is of a preliminary nature, and the authors have not attempted to express a numerical relationship in comparing the value of various disinfectants. This could, however, be dono by determining the relative quantities of the disinfectant just necessary to entirely inhibit putrefaction during a given interval of time. The method can be employed both in testing coal-tar disinfectants and in other cases also, and both anaerobic and aerobic cultures may be made and tested by the method. Different disinfectants may be compared similarly. A. R. T. Apparatus for the Estimation of Catalase in Milk. R. Burri and W. Staub. (Zeit. Untersuch. Nahy. G c ~ u s s ~ . , 1909, 17, 88-89.)- The apparatus described is intended for the estimation of the catalytic action of different samples of milk, the oxygen liberated from hydrogen peroxide by the action of the enzyme being measured for this purpose.As is seen from the figure, the apparatus consists of a graduated tube, the tube being slightly enlarged below the graduations, so that the space between the zero-point and the stopper will hold exactly 13 C.C. A small cylinder of agar jelly is placed in the graduated portion of the tube, SO that its lower edge coincides with the zero point of the graduations; the tube is then inverted, 10 C.C. of the milk to be tested are introduced into the wider portion of the tube, and then 3.1 C.C. of a 1 per cent. hydrogen peroxide solution. The stopper is inserted cautiously, causing the excess of hydrogen peroxide solution (0.1 c.c.) to escape.The tube is then placed in an incubator at a temperature of 38" C., and the oxygen evolved read off after a definite length of time. w. P. s. The Differentiation of Enzymes in Milk by Means of Tests for Hydrogen Peroxide. C. H, La Wall. (Amer. Juwn. Pharm., 1909, 81, 57-59.)-The methods used for the detection of boiled or sterilised milk may be applied conversely to the detection of hydrogen peroxide. In Dupouy's method a pronounced blue coloration is obtained on adding to 5 C.C. of raw milk a few drops of an aqueous solution of paradiamido- benzene, followed by a few drops of hydrogen peroxide solution. The author's experiments show that this coloration io obtained on adding the paradiamidobenzene solution to a, raw milk containing down to 15 parts of absolute hydrogen peroxide per 100,000, Similarly, in Wilkinson and Peters' methodTHE ANALYST.161 (ANALYST, 1908, 33, 401), a blue zone is obtained with raw milk containing as little as 15 parts per 100,000 of hydrogen peroxide. Both methods are superior to the potassium chromate and sulphuric acid test for hydrogen peroxide. It was found that small amounts of hydrogen peroxide in milk (up to 3 parts per 1,000) could not be detected a few hours after the addition had been made, although the milk remained sweet for several days. On now testing this milk for enzymes by the two methods mentioned above, positive results were obtained by Dupouy’s test, but not by Wilkinson and Peters’ test.This difference was very pronounced in the case of milk containing From 15 to 30 parts of hydrogen peroxide per 100,000. In the presence of larger quantities (up to 3 parts per 1,000) the Dupouy test was prevented after several days, whilst the other test was immediately prevented. Hence, hydrogen peroxide destroys the enzyme that reacts in the latter test more rapidly than the enzyme in the Dupouy test. Eventually it inhibits the action of both enzymes, causing the milk to react like boiled or sterilised milk. C. A. M. Chemical Methods for Distinguishing Carbon Monoxide-HEmoglobin from OxyhEmoglobin. K. Burker. (Zeit. biol. Tech. m d Methodik, 1908,1,146 ; Zeit. anal. Chew., 1909, 48, 205-207.)-The author has investigated a large number of the proposed methods for the differentiation of carbon monoxide-hEmoglobin from oxyhEmoglobin, and has selected the following modifications of Zaleski’s and Welzel’s tests : The blood containing carbon monoxide and a control blood con- taining oxygen are diluted a hundred times with water, care being taken to agitate the carbon monoxide blood as little as possible, since the compound is unstable in the air.If the test is required to yield a rapid result with a transient effect, 5 C.C. of each of the solutions of blood are placed in two test-tubes, and treated with 5 drops of concentrated copper sulphate solution. The contents are mixed by inverting the tubes once, and the carbon monoxide blood should then show a purple-red colour, whilst the ordinary blood is coloured green.Small dift’erences are best detected by looking at the contents of the tubes from above. I n a few minutes the carbon monoxide blood also turns greenish, but the difference may be made to last longer if only 1 drop of copper sulphate be employed. If the test is not required immediately, but is desired to be permanent, 5 drops of a freshly-prepared solution of tannin are used instead of the copper sulphate. I n the case of the carbon monoxide blood, the flocculent precipitate which is formed remains rose-red in colour ; in the case of the ordinary blood, it gradually becomes dirty red and finally brownish, and the difference remains perceptible for months. The tube containing the carbon monoxide blood must be tightly corked whilst the test is effected. J. F.B. The cylinder must be tightly corked. Estimation of Reducing Substances in Urine. J. E. Abelous. (Conzpt. Rend. SOC. Biol., 1908, 62 ; through Bull. SOC. Chinz., 1909, [iv.] 5, 78-79.)-Ten C.C. of the urine are mixed with 0.5 C.C. of a 1 per cent. solution of indigo carmine, and slowly titrated with & bromine solution until the colour becomes distinctly yellow, without any greenish tint. Each C.C. of bromine solution consumed by the reducing substances corresponds to 0.0008 gram of oxygen. Cold bromine in neutral or acid162 THE ANALYST. manometer, and the stopper is rotated until solution does not oxidise urea, creatinine, xanthine, or hippuric acid. Uric acid is oxidised, and should therefore be removed beforehand by means of basic lead acetate, which does not precipitate the other reducing substances in urine.The only precaution to be observed in the titration is not to have the liquid alkaline. C. A. M. Fermentation Saccharometer. H. Breddin. (German Pat., 206-399, April 1, 1908; Chem. Zeit. Rep., 1909, 33, 69.)-In this apparatus a manometer (2) is fixed to a stand, The longer arm of the manometer terminates in a closed bulb; I 7+ 1 the shorter arm carries a side-tube ( 5 ) , and is connected by way of the tap (6) with a com- pression cylinder (7), in which a piston can be moved up and down. The stopper of the fermentation vessel is held down by a screw clamp (14) ; it is hollow, communicating with the interior of the vessel, and, when in a certain position, also with the side-branch of the manometer by means of a small hole (12) and the tube (13). When in use, a certain volume of liquid is placed in the fermenta- tion vessel, the yeast is added, and the volume is made up to a gauge mark by the addition of water. The stopper is closed, and the vessel is placed in the incubator. When fermentation is complete, the vessel is cooled to the temperature of the room, the side-arm ' the hole (12) communicates with the tube (13). The pressure of the gas produced by the fermentation can then be observed on the manometer, the tap (6) being closed. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9093400158

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

162 THE ANALYST. ORGANIC ANALYSIS. The Influence of Acetanilide, Glycerin, and Other Substances, on the Estimation of Alcohol. L. E. Warren and H. C. Fuller. (Amer. Journ. Pharm., 1909, 81, 66-72.)-Experiments described in detail show that, although acetanilide volatilises to some extent in the distillation of alcohol and water, the quantities passing over are insufficient to affect the results of the estimation of alcohol. Similar conclusions were drawn from estimations of alcohol in mixtures containing, in addition to water, glycerin, antipyrin, caffeine, bromides OE potassium and sodium, and sugar. C . A. M. Estimation of the Acidity of Soil. H. Suehting. (Landw. Versuchsst., 1909, 70, 13 ; Chem. Zeit. Rep., 1909, 33, 114-115.)-Tacke’s method of estimatingTHE ANALYST.163 the acidity of soil has the drawback. that, as soon as the calcium carbonate comes in contact with the soil, organic substances are decomposed, with the liberation of carbon dioxide. The author's attempts to improve upon this method have shown that all strong alkali hydroxides and carbonates cause far-reaching decomposition in the organic substances. Probably they have a hydrating action upon neutral bodies, such as acid anhydrides or lactones, forming salts with them, carbon dioxide being meanwhile liberated from the carbonates. Hence it is necessary to employ the calcium carbonate method. In further experiments it was found that, after treating the soil with calcium carbonate for three hours in a current of hydrogen, as in Tacke's method, a slight evolution of carbon dioxide still continued for a long time.This was attributed to decomposition of organic matters in the soil, and not to the action of micro-organisms. Cooling the soil to 0" C. did not prevent this decom- position. C. A. M. Determination of Carbon by Means of the Bomb Calorimeter. J. A. Fries. (Journ. Anter. Chenz. SOC., 1909, 31, 272-278.)-The author has succeeded in 80 modifying the construction of the top of the Atwater-Hempel bomb as to make an accurate determination of carbon possible after observing the heat of combustion of the material in the bomb. As will be seen from the figule, the top has two separate openings and valves, an inlet terminating on the underside of the cover, and an outlet, extending by means of a fine platinum tube to within about inch of the bottom of the bomb.This platinum tube need not be very heavy. The platinum capsule containing the substance to be ignited is supported on one of the two heavy platinum wires which conduct the current for ignition. Outside the bomb, on the cover, the threaded projections of the inlet and outlet valves point in opposite directions, each being easy of access in connecting with absorption-tubes, etc. For a determination of carbon, a, charge of material large enough, if possible, to produce 4,000 to 5,000 calories is taken, and prepared exactly as in the determination of the heat of combustion, namely, voluminous or powdered material is pressed into tablets to prevent it from being projected off the capsule. After weighing, the pressed charge is placed in the platinum capsule, and this is attached to one of the wires in the bomb, so that the sub- stance comes into direct contact with the fuse-wire.The bomb is then charged with oxygen at 20 atmospheres pressure, and completely immersed in water in order to insure that no leak of gas is occurring. With the bomb standing to some depth in cold water the substance is ignited, and after a minute or two the bomb is removed from the water, carefully wiped, secured in its clamp, and connected to the absorption apparatus. This consists of four glass- stoppered U-tubes (5 inches long by {- inch diameter). The first and last U-tubes contain small granulated pumice saturated with aulphuric acid, and the two middle164 THE ANALYST. tubes are filled with finely granulated soda-lime. One of the acid-tubes is connected directly with the gas outlet of the bomb, and the end acid-tube is connected with a small wash-bottle containing water, by means of which the rate of gas passing can be observed and regulated.This small bottle is connected finally with a large aspirator-bottle filled with water, and the water in the latter turned on, and all the stoppers in the U-tubes opened. The apparatus should stand the suction of 2 feet of water-pressure without leakage. The valve of the bomb is next slowly opened, and the outflow of gas regulated, the normal rate being about 500 C.C. per minute. When the pressure of gas in the bomb is equal to that of the outside air, purified air is drawn through the bomb until d l the carbon dioxide is removed, which is always the case if 9 litres of air are aspirated through a bomb of about 400 C.C.capacity. The increase of weight in the two soda-lime tubes and the last acid-tube represents the amount of carbon dioxide produced. At ordinary room-temperature, and with a flow of about 250 to 500 C.C. per minute, no nitric acid from the bomb will come over with the first 9 litres of air, but traces of acid may be drawn over if more air is used. I t is important to ascertain whether the combustion has been complete, since even a small quantity of unburnt, or only partially burnt, matter will appreciably affect the results. Benzene-like or sooty odours in the gases evolved also denote incomplete combustion. The results obtained by this calorimeter are accumte, determinations on two pure organic compounds containing 69 and 94 per cent.of carbon respectively giving figures varying only 0.05 per cent. from the theoretical. Other materials examined by single determinations in the calorimeter gave results varying from -0.14 to + 0.22-per cent. of carbon as compared with the copper oxide method. A. R. T. Characteristics of Certain African Fats. (BUZZ. Imp. Inst., 1908, 6,369-380.) -Samples of ‘‘ Shea” butter imported as fat, and extracted from nuts obtained from Nigeria, the Gold Coast, and the Sudan, gave very similar analytical values. Fat from the seeds of a species of Mimusops resembled that derived from the seeds of Mim.zisops Djnve (BNALYST, 1908, 33, 330), whilst the fat from samples of u Dika ” nuts agreed in general characteristics with that examined by Lewkowitsch (ibid., 1905, 30, 394).The fat from Pentadesmn butyracea (Sierra, Leone) was a greenish- yellow substance with an d o u r like that of Shea butter. I t might be used in the manufacture of edible fats. The kernels and the husks of ‘‘ Mafoureira ” nuts yielded 54.46 and 50.37 per cent. respectively of dirty green solid fats, which could not be bleached by any of the ordinary processes used in soap-making. The seed cake was very bitter and unsuitable for feeding stuffs (Daniel and McCrae, ibid., 1908, 33, 276). The fruits of a species of Pycnaizthus, probably P. Konzbo, contained an inner nut covered with a false aril corresponding to the mace of the nutmeg, for which the seeds are frequently mistaken, though devoid of odour and containing no volatile oil.The b b mace ” resembled ordinary mace in form, but was smaller, darker in colour, and odourless, and had an oily, acrid, bitter taste. It yielded 57.04 per cent. of an orange-red oil, which gave a semi-crystalline deposit on standing. On treatmentTHE ANALYST. 165 The following analytical values were with alkalies it was coloured deep violet. obtained with these fats : Fat. Shea butter Lagos gerian nuts .. DO. from Ni Mimusops fat .. Dika fat .. Do. ... .. Penta desma butyracea fat Mafoureira fat from kernels Do. from huske P ycnant hus seed fat .. P y c n a 12 t h us " mace " oil .. Specific Gravity 1000 at - C. 15-5O 0.862 0'8691 99" I t -c. 155" 0.860 0-863 - 0.859 - - 0.886 0.866 99" at - - C. 15" Acid Value.1S.O 7.6 25.3 12.6 1-8 3.6 36.7 17-7 21.0 40.7 Saponi- fication Value. 179.0 181.5 18i.6 250.0 243.8 190.1 200-3 209.7 235-245 21 4 Iodine Value. 5s *7 62.0 56.2 3.34 4-2 41 -8 52.6 71.6 48'9 77.45 Hehner Value. Reichert- Meissl Value. - 2% nil - - nil - - __ - UnsLIponi fiable Matter. Per Cent. 1.5 6 -3 2 *6 (cima) - 1.47 1 '4 1.3 - - Molting. Point. Jolidifica- tion- Point of Fatty Acids. O c. 52 - 4 7 . s - - 5 0 7 53.2 45 -4 45.5 35 C. A. M. The Use of Cinchonamine in the Gravimetric Estimation of Nitrates. B. F. Howard and 0. Chick. (Joum. SOC. C7zenz. I d . , 1909, 28, 53-56.)-Owing to the comparative insolubility of cinchonamine nitrate in water, especially in solutions acidified with hydrochloric acid, the authors recommend a solution of cinchonamine hydrochloride as a reagent for the estimation of nitrates.A large excess of the reagent is neceesary to insure complete precipitation-at least 0.6 gram of the alkaloidal salt for 0.1 gram of potassium nitrate-and an excess of hydrochloric acid is added to the mixed solutions. After standing twelve hours the liquid is filtered and the precipitate on the filter-paper washed with water, not more than about 100 C.C. of wash-water being allowed for each gram of the precipitated nitrate. The method is stated to be as accurate as the nitrometer method, but is slower. It may be employed for the estimation of all nitrates except those of metals giving insoluble chlorides or oxy-chlorides. Thus, it is unsuitable for the examination of bismuth subnitrate, but has been employed with satisfactory results in the analysis of the nitrates of potassium, quinine, and urea.As a qualitative test the reagent is capable of detecting 1 part of nitric acid in 100,000 parts of water, though the limit of sensibility of the test in glacial acetic acid is 1 : 500. The quantitative examina-166 THE ANALYST. tion of a potassium nitrate solution by the above method, as compared with the nitrometer, gave the following figures : Mean of Pour Determinations. Nitrometer method : KNO, per cent. ... ... 97.55 Cinchonamine method : 9, ... ... ... 97.3 The cinchonamine hydrochloride is an expensive reagent, but it can be recovered after use. A. R. T. A Drying Oil from Ricinodendron Heudolitii Seeds. (B.zdZ. Imp. Iqzst., 1908, 6, 367-369.)-The kernels of the seeds of this Southern Nigeria plant, known as '' Nsa-sana " seeds, yielded 47.0 per cent.of a pale yellow oil with a taste resembling that of arachis oil. Exposed in a thin layer, it gave a dry film in a few hours, and from practical tests it appeared to stand between linseed and tung oils in its properties. It had the following analytical values: Specific gravity at 15' C., 0.9347 ; acid value, 1.2 ; saponification value, 184.7 ; iodine value, 148.2 ; Hehner value, 94.1 ; Reichert-Meissl value, 1.9 ; unsaponifiable matter, 1.2 per cent. ; and solidification-point of fatty acids, 34.5' C. C. A. M. The Estimation of Fatty Acids in Soap. G. Fendler and L. Frank. (Zeit. angew. Chem., 1909, 22, 252-261.)-The authors show by test analyses that the only method of obtaining accurate results in the estimation of the fatty acids in cocoanut and palmnut oil soaps is to convert the fatty acids into alkali salts by titrating their ether-alcoholic solution with alcoholic sodium or potassium hydroxide solution, to evaporate the liquid, and to dry the residue at 103" to 105" C.Luring's volumetric method (Seifenfubrilcaizt, 1907, 53)' in which the liberated fatty acids are melted in a special flask by the introduction of hot water and measured in EL graduated side tube, is only suitable for the control of factory operations in the case of these soaps and of olive oil soaps. With linseed oil soaps it gives unreliable results, and it cannot be used with soaps from tallow and other fats of high melting- point. Hehner's method of weighing the insoluble fatty acids gives good results with linseed oil soaps, as do also the methods in which the liberated fatty acids are extracted by means of ether or petroleum spirit.I n either case, however, the fatty acids must be dried in a current of carbon dioxide to prevent oxidation. Estimation .of the fatty acids of linseed oil soaps as alkali salts gives too high results if the residue is dried in the air, whilst the method of estimating them as calcium salts from the amount of calcium oxide left on ignition also yields results considerably too high. For olive oil and tallow soaps the ordinary method of drying and weighing the separated cake of fatty acids gives approximately correct values, but much better results are obtained by Hehner's or the extraction methods.Estimation of the fatty acids as calcium salts gives approximately correct results with olive oil soaps, but in the case of tallow soap the results are too high. C. A. M. gharacteristics of Certain African Non-Drying Oils. (Bull. Imp. Inst., 1908, 6, 356-367.)--" Ikpan " seed oil was a pale yellow clear oil, obtained from seeds which appeared to be those of one of the forms of water-melon (Citrzsllzss vzslgaris).THE ANALYST. 167 Raphia wax ... Ditto.. . ... '' INOY " kei*itcZ oil from Southern Nigeria was pale yellow in colour, and deposited a small amount of solid matter on standing. The high acid values given by the oils from the '' ben " seeds were attributed to decomposition of the seeds before extrac- tion. The oil expressed from the seeds of Calodeitdron capeizse, a tree growing in East and South Africa, was pale yellow, and had a pleasant odour and somewhat bitter taste.Bnlanites egypticn oil, as obtained from Northern Nigeria and extracted from seeds from the Sudan, was a yellow liquid without pronounced odour or taste. It consisted of glycerides of oleic acid, 33 per cent.; linolic acid, 33 per cent. ; and palmitic and stearic acids, about 34 per cent. The following analytical values were given by these oils : Specific Gravity a t Acid Saljouification Iodine Melting- 99" c. Value. Value. Value. Point. 15 '5" O c. 0.836 4.9 51.3 7-68 82 0.832 6.5 50.3 10- 70 83 Oil. (' Ikpan " seed oil ... '' Inoy " seed oil (1) . . . 9, 9 , (2) . * . '' Ben " seed oil, cold pressec J, ,, hot pressed Calodendroiz caiiense oil .. . Balanites egyptica oil, from Nigeria ... ... Balanites Bgyptica oil, from Sudan fruits ... ... Specific Gravity at 16" C. 0.9280 0-8960 0.9140 0.9018 0.8984 0.9190 0.9190 0.9187 Acid Value. 1.40 39 *70 45.30 49-71 100.51 27-00 5.00 1-40 Saponifi- cation Value. 196.50 184.49 192.90 179.20 178.70 192.00 196.70 194.20 Iodine Value. 107.0 89-7 90.9 100.3 88.0 98.4 92-5 98.2 lehner Value. - 93.0 94.5 - - 95.2 98.6 Reichert Meissl Value. Solidi- fication Poiiit of Fatty F d s , C. - 22.0 24.5 - - 35.0 34.6 34.0 C. A. M. Raphia Wax. (Bull. Imp. Inst., 1908, 6, 380-383.)-A wax closely resembling carnauba wax in physical properties, but differing considerably in its composition, occurs as a, whitish deposit on the under side of the leaves of the raphia palm (napkin ~ z t f i a ) .In a test experiment the yield of wax was 0.75 per cent. of the weight of the leaves used. Two samples examined were of a yellowish-brown colour, and sufficiently brittle to be powdered. They gave the following analytical values :168 THE ANALYST. I t is suggested that, if exported free from grit and of a pale colour, this wax might be profitably used as a substitute for carnauba wax in boot-polishes, candles, etc. C. A. M. Estimation of the Thermal (Maumene) Value of Fats and Oils. Tortelli. (Chem. Zeit., 1909, 33, 125-126 ; 134-135 ; 171-172 ; 184-185.)-1t is shown that the rise in temperature which takes place when an oil is mixed with sulphuric acid is a constant for one and the same oil if proper precautions be taken in carrying out the test.The author employs a vacuum-jacketed tube in which the oil and acid are mixed, and takes 20 C.C. of oil and 5 C.C. of sulphuric acid of specific gravity 1,8413 for each estimation. The following thermal values are given for various pure oils and fats : olive oil, 44 ; cottonseed oil, 78 ; sesame oil, 71 ; rape oil, 60.8; earthnut oil, 60; grape seed oil, 73.6; maize oil, 82; poppy oil, 88.4; almond oil, 50.7 ; apricot kernel oil, 60.5 ; hazel nut oil, 48 ; cherry kernel oil, 52.3 ; mustard oil, 58.6, castor oil, 74 ; hemp seed oil, 89 ; linseed oil, 124.4 ; stillingia oil, 136.2 ; sheep's-foot oil, 41-5; ox-foot oil, 40.4; horse-foot oil; 58.6; lard oil, 44.9; whale oil, 75.6; seal oil, 72.1; cod-liver oil, 102; sardine oil, 112.5; palm oil, 31.5 to 37.9 ; shea butter, 41.4 ; cacao butter, 26.3 ; stillingia tallow, 37.3 ; palm kernel oil, 23.4; cocoanut oil, 22.4; lard, 39; horse fat, 53.7; tallow, 31.5 to 41.3; butter, 31.3.The thermal value is also a measure of the iodine value of a fat; the iodine value of a non-drying oil (olive, etc.) is obtained by multiplying the thermal value by 1.82 ; for semi-drying oils (rape oil, etc.) the factor is 1.60 and for drying oils 1-48. w. P. s. Estimation of Essential Oils. M. Klassert. (Zeit. Untersuch. N a b . Genussm., 1909, 17, 131-132.)-1t is pointed out that when the ethereal solution of an essential oil is evaporated as described by Reich (ANALYST, 1909, 34, 20) until entirely free from ether, the residue of essential oil may still contain an appreciable quantity of water derived both from the air and from the ether.The author, there- fore, recommends that the evaporation be carried out as follows. The ethereal solution is transferred to a basin which is placed under a bell-jar. A glass tube is fitted in a tubulure in the side of the bell-jar, the end of the tube being bent so as to be just above the surface of the ethereal solution. A current of dry air is aspirated through the bell-jar ( a second tube entering the top of the bell-jar for this purpose) at the rate of about sixty bubbles a minute until practically all the ether has been evaporated. A tap on the upper tube is then closed while the water-pump, which is used for drawing the current of air through the bell-jar, is kept working for 8, further two minutes; the pressure in the bell-jar is thus reduced and the moisture evaporates quickly.After five minutes, the basin is placed in a desiccator, until it and its contents have attained the ordinary temperature, and then weighed. Owing to the low temperature produced by the evaporation of the ether, there is but little risk of loss of volatile essential oil. w. P. s. The Detection of Methylaniline and Dimethylaniline in the Presence of (Archiu Pharm., 1909, 247, 77-79.)-A few grams of the &oh Other. H. Emde.THE ANALYST. 169 substance are dissolved in concentrated hydrochloric acid, and the solution added drop by drop with continual shaking to an excess of an aqueous solution of platinum chloride. The precipitate is collected and recrystallised from alcoholic hydrochloric acid (96 per cent.alcohol containing 7 per cent. of HCl), and a separation of the platinum double salts thus effected. For the detection of methylaniline alone the precipitate is boiled with just so much water that no yellowish-red crystals remain at the bottom. On cooling, the more insoluble methylaniline compound separates in well- formed crystals, which may be purified by recrystallisation. The two compounds may be distinguished from one another by the difference in the form of the crystals, in the melting-points, and in the amounts of platinum left on ignition. The platino-chloride of methylaniline, [C,H,NH(CH3).HC1],PtC14, forms orange-coloured granular crystals which melt a t 199" C. (turning black and decomposing) and contain 31 -24 per cent.of platinum. The platino-chloride of dimethylaniline, [C,H,N(CH3)2.HCl]2PtC1,, crystallises in orange-red needles, which melt (with decomposition) at 173" C. and contain 29.89 per cent. of platinum. Five per cent. of methylaniline was readily detected in this way in dimethylaniline. C. A. M. Inversion of Maltose. Pieraerts. (Bull. ~ S S O C . Chinz., 1908, 26, 662 ; Chem. Zed. R e p , 1909, 33, 94.)-Maltose is completely hydrolysed by heating with citric acid, and the resulting solution is quite colourless. Fifty C.C. of the solution, containing about 2.5 per cent. of the sugar, and 10 C.C. of 20 per cent. citric acid solution are placed in a flask, and heated for two and a half hours in an autoclave, at a pressure of 1-5 atmospheres. The contents of the flask are then cooled rapidly, transferred to a 100 C.C.flask, 2 C.C. of (( alumina cream " are added, and the mixture is diluted with water to a volume of 100 C.C. The quantity of actual sugar is then determined gravimetrically or polarimetrically. The inversion may be carried out by heating the solutions under a reflux condenser, but the time taken is longer, and there is danger of discolouring the solution. w. P. s. Detection of Methylpentoses in Presence of Pentoses. L. Rosenthaler. (Zeit. anaE. Chem., 1909,48,165-172.)-The spectrum reaction of Widtsoe and Tollens, depending on the existence of a characteristic line between the green and blue when the liquid is warmed with hydrochloric acid, can be used for the detection either of methylfurfural in distillates, or of methylpentoses in the original substance.I n the case of pure rhamnose 0.44 mgm. can be detected directly without distillation, but if more than ten times the above quantity of pentose be present at the same time, the liquid becomes too dark in colour for direct observation. The author describes another test for the detection of methylpentoses, depending on the use of specially- purified acetone. If the substance be heated in a tube with about 10 C.C. of concen- trated hydrochloric acid and 1 to 2 C.C. of acetone for ten minutes in the boiling water-bath, a mulberry-red coloration is developed, which shows a sharp absorption band in the yellow, extending on both sides of the L) line. Pentoses under similar conditions give brown liquids without a characteristic spectrum.The red coloration can be extracted by shaking the solution with a colourless liquid phenol, such as170 THE ANALYST. creosote or guaiacol, and the extract diluted with glacial acetic acid for spectroscopic examination. This reaction admits of the detection of 0.15 mgm. of rhamnose in presence of ten times the quantity of pentose. This test can also be applied to distillates containing methylfurfural, but the Widtsoe and Tollens test is more sensitive. Furfural also gives a red coloration, but it is destroyed by heating for ten minutes. For the detection of furfural in presence of methylfurfural the aniline test is by far the most delicate. The author describes also another test, depending on the use of resorcinol or pyrogallol, which can also be applied in the presence of methyl- furfural.If the furfural distillate be treated with an equal volume of concentrated hydrochloric acid and a few crystals of resorcinol or pyrogallol, the liquid becomes gradually darker, the right half of the spectrum is obscured, and, after a time, an absorption band appears in the red and spreads towards the middle. If the quantity of furfural be small, this may not occur, but a sharp absorption band is observed between the C and D lines. When the whole of the spectrum is obscured, a precipitate forms; if this be filtered off it is found to give a blue-violet solution in glacial acetic acid, which shows the absorption band between C and D. J. F. B. Methods for the Analysis of Hard-Vulcanised Rubbers. G. Hubener.(Chem. Zeit., 1909, 33, 144-145, 155-156.)-The two simple methods hitherto proposed for the analysis of vulcanised rubber-those of Axelrod (Gumnzi Zeit., 1907,1229) and Budde (ibid., l907,1205)-have failed to give satisfactory results in the author’s hands in the case of hard rubbers or vulcanites. The method now proposed by the author is based on the determination, first of the quantity of bromine absorbed by the unsaturated bonds of the unvulcanised caoutchouc still present in the sample, and then of the sulphur combined with the vulcanised caoutchouc of the sample. The sum of the equivalents of the two is a measure of the original double bonds, and hence of the caoutchouc present before vulcanisation. The difficulty of finding a solvent which would carry the bromine into the centre of the particles of rubber was surmounted by the observation that bromine water readily penetrates even the hardest kinds of vulcanised rubber, and brominates them quantitatively.The method of procedure is as follows: 0.1 gram of finely-rasped vulcanite are placed in an Erlenmeyer flask with about 75 C.C. of water and 10 C.C. of bromine, and the flask is stood on a moderately warm sand-bath. When most of the bromine has dis- appeared, the heat is increased until no more bromine remains. If sufficient bromine has been used, the brown particles of vulcanite will have been converted into a white flocculent precipitate. This is filtered off and washed with hot water. The filtrate contains the uncombined sulphur of the vulcanite in the form of sulphuric acid, which is estimated in the usual way.The precipitate is placed in a flask with 25 C.C. of & silver nitrate solution and 10 to 15 C.C. of pure concentrated nitric acid, and the liqufd is boiled until the nitric acid vapours begin to come off. When the total volume has been reduced to about 15 c.c., the liquid is diluted with water, 5 C.C. of a saturated solution of iron alum are added, and the excess of silver nitrate is titrated back with TG thiocysnate solution. The calculation is then made on the assumption that 320 grams of bromine are absorbed by 136 grams of caoutchouc hydrocarbon, C,,,HIG, and the percentage of caoutchouc not in combina-THE ANALYST. 171 tion with sulphur is thus found. The sulphur in combination with caoutchouc (vulcanisation-sulphur) is found from the difference between the total sulphur and the uncombined sulphur (determined above).The total sulphur is estimated by heating 1 gram of the sample with concentrated nitric acid on the water-bath until the acid has evaporated, mixing the residue with a mixture of 5 parts of sodium carbonate and 3 parts of nitre, and heating gently until fused. The melt is dissolved in water, the solution filtered and evaporated to dryness with hydrochloric acid, the sulphuric acid being estimated in the usual way. The vulcanised and original caoutchouc corresponding to the sulphur of vulcanisation are calculated. on the following equivalents : S, = Cl,Hl,S2 (vulcanised rubber) = Cl,Hl, (original caoutchouc}. The caoutchouc so found, added to the caoutchouc calculated from the bromine value, gives the total original caoutchouc.According to another modification of the method, the brominated precipitate may be collected on a tared filter and washed, first with water, then with alcohol, and finally dried at 60" C. The precipitate is then incinerated. The weight of the ash and the weight of the caoutchouc-sulphide, calculated from the vulcanisation-sulphur, are then deducted from the weight of the dried precipitate ; the balance represents the weight of caoutchouc tetrabromide, from which the weight of pure caoutchouc can be calculated. In the case of certain mineral loading substances which contain or combine with sulphur, the ash must be analysed and the results taken into account in the determination of the uncombined sulphur.J. F. B. The Examination of Turpentine Oil. A. E. Paul. (Joui-n. h2d. Eny. Chent., 1909, 27; Chem. Zeit. Rep., 1909, 33, 104.)-The following modification of the method of polymerisation with sulphuric acid enables 1 per cent. of mineral oil in turpentine oil to be detected with certainty : One hundred C.C. of the sample are distilled by means of a strong current of steam in a Kjeldahl flask, and the distillate and residue freed from water by filtration. The distillate is returned to the flask, gradually treated, with constant shaking, with 500 C.C. of concentrated sulphuric acid, and thoroughly cooled. After the addition of 25 C.C. of water, the liquid is again distilled with steam until 100 C.C. have passed over. Should more than 8 C.C.of oil remain in the flask, the oil must be regarded as adulterated. This residue is added to the residue from the original distillation, and the mixture introduced drop by drop into three times its volume of fuming nitric acid contained in a separating funnel cooled with ice. After removal of the acid layer, the oil is treated once more with fuming nitric acid, then twice with ordinary nitric acid, and finally washed several times with water. Pure turpentine oil gives a residue of only about 0.5 per cent., whilst only a trace of residue is given by wood turpentine oil. C. A. M. Analysis of Natural and Artificial Silk Fabrics. Coppetti. (Ann. Chim anaZ., 1909, 14, 47-51.)-The usual tests for distinguishing between natural and arti- ficial silks fail when these are weighted or impregnated with substances to make them incombustible.Most of the weighting compounds usually employed cannot be stripped by the ordinary reagents without destruction of the fibre. The authorThe bleached fibres arc placed on an object- glass, covered with a c o v e r - g l a s s , a n d treated with a drop of nitric acid, the effect being observed under the microscope. brown F r e s h fibres are treated w i t h con-, c e n t r a t e d s u 1 ph u r i c TABLE FOR THE IDENTIFICATION OF SILK FIBRES. . . . (Real silk.) (Artificial gelatine yellow. silk. j* ... . . . (Tussah silk.) ’Dissolved in the c o 1 d ; give b l u e colora- tion with di- phenylam i n e [ F r e s h fibres , acid. , reagent ... F r e s h fibres are treated w i t h t h e i o d i n e re- agent. Blue 1 F:t p:t: Dissolved . . . coloration. 1 c h r o m i c] Not dissolved.. . a c i d r e - I agent. I [ F r e s h fibres [ are t r e a t e d J V i o l e t - b l u e with iodine coloration . . . . a n d s u l - 1 2 5 F (Vegetable silks. ) ( M e r c e r i s e d M cotton.) t 4 (Artificial silk of 9 cellulose.) 1 (Artificial c o l l o - dion silk.) * S o t dissolired hy Schmeitzer’s nor Lowe’s reagents. Rapidly dissolved by 40 per cent. potassiu~ll hydroxide. -f Verified by microscopic appearance. Ordinary cotton gives same reactioii, Sature of silk shown by diphenylalninc test.THE ANALYST. 173 finds, however, that weighted silks, whether natural or artificial, can be reduced to a condition suitable for the application of the tests by the following treatment: A piece of the fabric is placed in a lead capsule with some commercial hydrofluoric acid. After digestion for five to ten minutes the sample is washed and boiled with a solution of soap. It is washed again, and boiled with a 5 per cent. solution of hydrochloric acid; next, it is dipped in a solution of sodium hypochlorite, then again into hydrochloric acid; lastly, it is washed, pressed, and dried. An alternative method of bleaching is by permanganate, followed by sulphurous acid. The silk, being now stripped both of mineral and colouring matters, can be tested in the usual manner. The author has devised an analytical scheme for the differentiation of the various chemical types of silk which greatly facilitates the work. If the fibres still retain too much colour to ahow a stain with nitric acid (see table), the animal fibres may be distinguished from the vegetable by their solubility when warmed on a glass slide with a 20 per cent. solution of potassium hydroxide. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9093400162

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

THE ANALYST. 173 INORGANIC ANALYSIS. Apparatus used in Rapid Methods of Eleetro-Analysis. Analysis of Brass. T. S. Price and T. C. Humphreys. (Journ. SOC. Chenz. Ind., 1909, 28, 117-124.)-After describing the various methods and the apparatus used for rapid electrolytic work, and quoting experiments which show that, with rotating electrodes, copper cannot be completely deposited from a nitrate solution, unless sulphuric acid or a sulphate be added, the authors give two methods for the estimation of copper and zinc in brass : (1) About 0.7 gram of brass is dissolved in 4 C.C. of concentrated nitric acid and a little water. The solution, filtered, if necessary, from stannic hydroxide, is transferred to the tap funnel in which the electrolysis is carried out, diluted to 75 or 100 C.C.with water, and electrolysed, after adding 1 C.C. of sulphuric acid, using a current of 3 a m p h s at 3 volts for twenty to thirty minutes. The cathode, which consists of a cylinder of platinum wire gauze (4 meshes per square millimetre) 40 mm. long and 20 inm. in diameter, is rotated from a bicycle hub; the stationary anode consists of a double circle of stout platinum wire, provided with four small vertical baffle plates (vide Price and Judge, Tmits. Faraday SOC., 1906, 2, 85). At the end of the electrolysis, the solution and cathode washings are run into a dish and evaporated to fuming, the residue is dissolved in a few C.C. of water to which a little sulphuric acid may be added, and 6 to 8 C.C. of a 25 per cent. solution of sodium hydroxide added until zinc hydroxide begins to separate.Enough ammonia is then added to dissolve this precipitate, and the solution is gently warmed and filtered, the insoluble ferric hydroxide being washed with hot water and ammonia, 6 to 8 C.C. of which are used altogether. The filtrate is acidulated with glacial acetic acid, and electrolysed for twenty minutes with a current of 2 amperes at 4 to 4.5 volts, using the cathode on which the copper has been deposited previously. (2) The solution of the brass, obtained as above and filtered from stannic hydroxide, if necessary, is evaporated until it becomes syrupy ; 3 C.C. of sulphuric174 THE ANALYST acid are then added, and evaporation continued to fuming. The residue is taken up in water, and the solution filtered from lead sulphate into an electrolysing funnel of 140 C.C.capacity. The copper is deposited, by using a current of 2.5 amperes at 2.5 volts for five to ten minutes, and a current of 0.5 ampere at 2 volts for another twenty minutes. The solution is then run into a, small beaker together with the wash-water, of which as little as possible should be used; 9 C.C. of ammonia solution are then added to the solution, which is heated to boiling and filtered back into the electrolysing funnel, the ferric hydroxide being washed with hot water and ammonia. The zinc is deposited in twenty to twenty-five minutes, using a current of 2 amperes at 3 to 4 volts. This method avoids the lengthy evaporation necessary with the first method after the copper has been deposited. Both methods give results which are within 0.16 per cent., and are generally much closer.The volume of the filtrate should be 75 C.C. A. G. L. The Influence of Chlorides on the Estimation of Nitrates. G. Perrier and L. Farey. (BUZZ. SOC. Chim., 1909, [iv.] 5, 178-180.)-The authors have studied the influence of chlorides on the colorimetric method of estimating nitrates devised by Grandval and Lajoux. I n each case 10 C.C. of the water or potassium nitrate solution were evaporated to dryness on the water-bath, and the residue treated with 1 C.C. of phenolsulphonic acid (phenol, 12 grams ; sulphuric acid of 66" B6., 144 grams), After a few minutes 10 C.C. of water were added, and then 10 C.C. of ammonia soh- tion (1: 3), and the resulting yellow coloration matched with that of a standard prepared from a solution containing 80.5 mgm.of potassium nitrate per litre. The results showed that chlorides, even in the amounts commonly found in drinking water (15 to 70 mgm. per litre) had an appreciable influence on the coloration, whilst if they reached 150 t o 400 mgm. per litre they rendered the method erroneous. Thus, in the case of a water containing 300 mgm. of chlorides per litre, only half the amount of nitrates present (10 mgm. instead of 20 mgm.) was found. This draw- back may be obviated by adding to the standard solution an amount of chloride equal to that in the water under examination. On now treating the residues from the two liquids with the reagent under the same conditions, the true amount of nitrates may be found. C. A. M.On the Volumetric Estimation of Copper and Chromium, and of Copper, Chromium, and Iron, in Admixture. E. Hibbert. (Journ. SOC. Chem. Ind., 1909, 28, 190-192.)-The methods described depend on reduction with a, standard solution of titanous chloride, and are especially applicable to the ash of mordanted fabrics. The metals must be present as cupric salt, chromic acid, and ferric salt, respectively. When copper sulphate and potassium bichromate only are present, copper and chromium are estimated together in one part of the solution by adding an excess of titanous chloride, and titrating back with a standard iron solution, potassium thiocyanate being added to the solution as indicator. In a second portion of the solution copper only is estimated after reducing chromium with sulphur dioxide and boiling off the excess, or else copper is removed by precipitation with hydrogen sulphide. In the filtrate chromium is reoxidised with sodium peroxide, theTHE ANALYST. 175 excess of the latter destroyed by boiling with ammonium chloride, and the chromic acid reduced by the titanous chloride solution.When copper, chromium, and iron, are present together, they are estimated together in one portion of the solution by direct titration with titanous chloride, potassium thiocyanate being added as indicator after the chromium has been reduced. I n a second portion the iron is estimated after removing copper as sulphide, boiling off hydrogen sulphide from the filtrate, oxidising the iron only by treatment with potassium chlorate and hydrochloric acid, and removing chlorine by thorough boiling.In a third portion iron and copper are estimated together, after reducing iron and chromium with sulphur dioxide, and reoxidising iron only with potassium chlorate and hydrochloric acid. Both methods give results differing from the truth by only a few tenths of a milligram on quantities of substance up to 0-2 gram. A. G. L. A New Method of Estimating Cuprous Oxide in Copper. G. Coffetti. (Gaxx. Chim. ItaZ., 1909, 39, 137-143.)-The method is based upon the fact that cuprous oxide is soluble, whilst copper, in the absence of oxygen, is insoluble in ammonia solution, The apparatus shown in the figure was devised by the author for the estimstion. The central bulb has a capacity of 100 c.c., and has side-tubes, A and B, and a small siphon, s, at the bottom.The top is closed by means of a rubber cork, through which is passed the stem of a small separating funnel. The sample of copper is introduced into the bulb, and placed on a layer of glass-wool to protect the siphon. The tube A is connected with a source of hydrogen, which previously traverses a series of washing-bottles, and then an empty bottle, into which, after expulsion of all air? a little concentrated ammonia is introduced to saturate the hydrogen before it enters the apparatus. Strong ammonia solution is next introduced into the apparatus itself without interrupting the current of hydrogen, which passes through the liquid and escapes through the tube A, the other end of which is connected with a tube opening into water.The apparatus is continuously shaken, and when the colour appears constant the amaonia solution is drawn off through the siphon-tube. The copper is subsequently washed with successive portions of freshly boiled water containing 10 per cent. of ammonia, until the liquid remains colourless, after which a fresh quantity (50 c.c.) of strong ammonia solution is introduced, and left in contact with the copper for four or five hours, this treatment being repeated until finally the liquid remains colourless. Throughout these operations the current of hydrogen is maintained. The united solutions and washings are acidified with nitric acid, and the dissolved copper estimated electrolytically and calculated into cuprous oxide. Test analyses quoted show that the method gives accurate results in close agreement with those obtained by Hampe’s method, over which it has the advantage of being applicable also to bronze and other alloys of copper.C. A. M.176 THE ANALYST. Estimation of Copper by Means of Potassium Permanganate. F. G. Hawley. (Eizg. and Mzn Jounz., 1908, 86, 1155 ; Chem. Zeit. Rep., 1909, 33, 87.)- 0.5 gram of copper ore is decomposed with 10 to 12 C.C. of a mixture of sulphuric and nitric acids (1 : 3), to which 4 to 8 drops of hydrofluoric acid are added if much clayey matter is present. The whole is boiled down to fuming, cooled, diluted with 35 C.C. of water, and neutralised with ammonia. Four C.C. of hydrochloric acid and 10 C.C. of a 20 per cent. sodium sulphite solution are added, the solution is heated to boiling after covering the beaker, 5 C.C.of a 4 per cent. potassium thiocyanate solution are added, and the boiling continued for one or two minutes more. After standing for five minutes, the precipitate of cuprous thiocyanate (together with the original insoluble matter) is filtered off, washed with a little warm water, and decomposed on the filter with a boiling 6 per cent. solution of sodium hydroxide, the alkaline solution being caught in the original beaker. This solution is acidified with sulphuric acid, ctud the thiocyanic acid formed titrated with a standard potassium permanganate solution, of which 1 C.C. corresponds to 0.01 gram iron or 0.00197 gram copper. A correction must, however, be made to allow for the solubility of cuprous thiocyanate in the acid liquid from which it was precipitated.I t is stated that by this method twenty copper estimations can be carried out in one and a half hours, with an accuracy not greatly inferior to that obtained by the usual methods. A. G. L. New Method of Attacking Ferro-Alloys, partieularly Ferro-Silicon. P. Nicolardot. ( A m . Chim. anal., 1909, 14, 62-64.)-The attack of refractory alloys, such as ferro-silicon, ferro-titanium, and ferro-chromium, as a preliminary to their analyeis is very difficult, neither the method of fusion with alkalies nor that of chlorination at a red heat being satisfactory. The author has found, however, that sulphur chloride attacks these alloys very readily, the only precaution necessary being that of preventing the escape of any of the volatile chlorides of the metals.Perro-silicon is completely decomposed at 70" C. ; ferro-chromium is only attacked at a temperature above 120" C. ; but the attack on ferro-titanium begins at 70' C. The decomposition of the alloy is effected in a, round-bottomed flask of 250 C.C. capacity. 0.5 gram of the coarsely powdered ferro-silicon is placed in the dry flask, which is then closed by a rubber cork through which passes a tube with a stopcock. Above the stopcock the fube takes the form of two concentric cylinders, the inner tube being graduated at intervals of 0.5 c.c., and having a capacity of about 4 c.c., the outer tube being extended beyond the inner one for the insertion of a stopper. The flask being thus closed is evacuated to a vacuum of 20 cm. of mercury, the stopcock is closed, and the connection with the pump dismounted.Two C.C. of sulphur chloride are placed in the inner tube and admitted to the flask without breaking the vacuum. The excess of sulphur chloride is washed away, and the contents of the flask are heated until the reaction begins. I t is allowed to proceed under control by alternately cooling and warming as required. When it is finished, the contents of the flask are thoroughly cooled, and a few drops of amrnoniacal water are admitted very cautiously. Lastly, the flask is gradually filled with water, care being taken that none of the vapours of silicon chloride escape. The absorption of these vapoursTHE ANALYST 1'77 by the water is assisted by inverting the closed flask several times.The rest of the analysis is conducted in the usual manner. J. F. B. Estimation of Lead in Copper Alloys. G. Gherardi. (Rassegiza Mineyai-in, 1908,29,251; Chem. Zeit. Rep., 1909,33,87.)-A rapid (' works " method for estimating lead in copper alloys consists in dissolving 0.5 gram to 5 grams of the alloy in nitric acid, filtering from insoluble stannic acid, evaporating the filtrate to fuming with sulphuric acid, diluting the residue with 20 C.C. of water, shaking in a centrifugal machine, and reading off the volume of lead sulphate obtained in a graduated tube. A. G. L. Electrolytic Estimation of Lead and Manganese with the Use of the Gooch Crucible. F. A. Gooch and F. B. Beyer. (Zeit. Anorg. Chenz., 1909, 61, 286-292.)-The authors have applied their simultaneous filtration and deposition method (ANALYST, 1908, 33, 296) to the estimation of lead and manganese.For lead, the liquid, which should contain 30 C.C. of concentrated nitric acid per 100 c.c., is continuously filtered during the electrolysis ; with a, current density of 4 ampkres per 40 sq. cm. at 5 volts, 0.15 gram of lead dioxide is completely deposited in about two hours. To prevent disturbance of the asbestos by the gases evolved at the bottom of the crucible, the dry layer of asbestos is moistened from outside the crucible with a drop of nitrobenzene. When deposition of the lead is complete, the acid liquid is displaced by a solution of ammonium nitrate without interrupting the current ; the deposit is finally washed with water, dried at 200" C., and weighed as PbO,, the error being up to 0*0004 gram.For manganese, 50 C.C. of a solution of manganese sulphate containing 6 drops (0.17 c.c.) of concentrated sulphuric acid are used. With continuous filtration, 0.1860 gram of manganese dioxide is completely deposited in 105 minutes, using a current density of 2 ampkres per 40 sq. cm. at 20-10 volts. It is more convenient, however, to electrolyse without filtration for about two hours, and then to complete the deposition by simultaneously filtering and electrolysing. The deposit is washed with water after interrupting the current, dried at 200" C., weighed as MnO,, ignited at a low red heat, and again weighed as Mn,O,. The error varies from nil to 0.0012 gram. A. G. L. On the Precipitation of Magnesium as Ammonium Magnesium Arsenate.E. Raffa. (Gaxx. Chim. Ital., 1909,39, 154-162.)-A solution of disodium ammonium arsenate prepared in an analogous manner to disodium ammonium phosphate (ANALYST, 1909, 73) precipitates magnesium almost quantitatively ; but, as in the case of other methods, the amounts of magnesium pyro-arsenate obtained by igniting the precipitate in a Gooch crucible are too low. This is partly due to the reducing effect of hydrogen formed from the ammonia, and this is not entirely prevented by carrying out the ignition in a, current of oxygen. The main cause, however, is the solubility of the ammonium magnesium arsenate. Applying the correction of Virgili of 1 mgm. for each 30c.c. of liquid, the author obtained results agreeing within about 1 mgm. of the calculated amount of magnesium pyro-arsenate (0.1889 gram). With greater quantities, however (0.3797 gram), the difference amounted to 2 or 3 mgm.Hence the volume of the precipitate has an influence upon the solubility. For these reasons178 THE ANALYST. the author concludes that the phosphate method should always be preferred for the estimation of magnesium. C. A. M. Colorimetric Estimation of Phosphoric Acid. J. Pouget and D. C ~ O U - chak. (BUZZ. SOC. Chinz., 1909, [iv.] 5, 104-109.)-A method is based upon the fact that, on adding a dilute solution of an alkaloid to a solution containing sodium molybdate, nitric acid, and phosphoric acid, a turbidity is produced, the intensity of which, when the other factors are the same, depends upon the proportion of phos- phoric acid.The authors have obtained the best results with strychnine as the alkaloid, and have found the following reagent, which should be recently prepared, extremely sensitive: Ten C.C. of a 15 per cent. solution of sodium molybdate are treated with 2.5 C.C. of pure nitric acid, followed by 1 C.C. of a cold saturated solution of strychnine sulphate. On adding 2 C.C. of this reagent to a solution containing 3.7 per cent. of nitric acid, the liquid remains permanently clear in the absence of phosphoric acid; but if as little as 0.005 mgm. of phosphoric acid be present, an opalescent tint appears after five to ten minutes, and becomes very pronounced after twenty to twenty-five minutes. The test is thus capable of detecting 1 part of phosphoric acid in 20,000,000.Examined by transmitted light in the colorirneter, the opalescence appears of a yellowish-brown tint, and, provided the acidity (as nitric acid) lies between 1.5 and 4.2 per cent.-preferably 3-7 per cant.-is proportional to the quantity of phosphoric acid in amounts between 0.02 and 0.1 mgm. per 100 C.C. With the most favourable proportion of nitric acid (3.7 per cent.), the proportion between the colour and the amount of phosphoric acid is maintained even in solutions containing silica, and various metals that often accompany phosphoric acid (calcium, iron, magnesium, aluminium, potassium, sodium). The relationship is still main- tained when the amount of calcium oxide is 20,000 greater than that of the phosphoric acid, but is destroyed by an amount of iron 1,200 times that of the phosphoric acid.In making a colorimetric estimation the nitric acid solution of the substance (containing 0.01 to 0.05 mgm. of phosphoric acid) is evaporated to dryness on the water-bath, and the cold residue treated with 10 C.C. of 35 per cent. nitric acid. The basin is shaken at intervals during twenty minutes, and the liquid then decanted or filtered into a graduated 50 C.C. flask, and diluted to 47 C.C. with the washings. It is next treated with 2 C.C. of the reagent, thoroughly shaken, and made up to 50 C.C. The standard solution for the comparison is prepared by adding 10 C.C. of the nitric acid to 3 C.C. of a solution of phosphoric acid (10 mgm. of P,O, per litre), diluting the liquid t o 47 c.c., adding 2 C.C. of the reagent, and making up the volume to 50 C.C.After standing for about twenty minutes the liquids are matched in the colorimeter, and the amount of phosphoric acid calculated from the thickness of layer required of the standard solution. Arsenic, if present in quantity exceeding two or three times that of the phosphorus, interferes with the test, and should be removed beforehand. I n the case of substances containing very large amounts of iron or calcium, the solution containing the iron in the ferric condition is reduced by zinc and hydrochloric acid, and evaporated almost to dryness to expel the excess of acid. One C.C. of a ferric solution containing several mgnis. of iron is next added, and the liquid diluted and h a t e d with regulated quantities of pure calcium carbonate.The precipitate isTHE ANALYST. Parts per Xillion. 179 Parts per Salts. Million. collected, washed two or three times, and redissolved in 10 C.C. of 35 per cent. nitric acid, and the phosphoric estimated as described above. C. A. M. Colorimetric Estimation of Phosphates in Presence of other Salts. C. Estes. (Jouurn. Amer. Chem. SOC., 1909, 31, 247-250.)-The author has investi- gated the action of certain salts present in solutions in which it was sought to determine colorimetrically the amount of phosphate by means of the molybdate method, using the Schreiner colorirneter. Previous investigators have shown that ammonium salts and certain chlorides influence markedly the colour of phospho- molybdate solutions, and the author has now studied the action of certain other salts which may occur in soil and plantl extracts, in meat, and in the products of the oxidation of organic matter with sodium peroxide, magnesium nitrate, nitric and sulphuric acids, etc.I t is now shown that sodium nitrate, and probably potassium ethyl sulphate, at first decrease the normal iriiensity of colour in proportion to the quantity present, but as the salt is increased in amount a fixed value is reached. Sodium sulphate, potassium acid sulphate, magnesium sulphate, sodium chloride, and an excess of nitric acid, all greatly decrease the coloration, and, if present in large amount, only a trace of colour appears ; but the errors are not proportional to the amount of salt present. Nitrates of calcium and magnesium at first cause a decrease of colour, but with much larger amounts the normal intensity is almost restored.The quantity of the different salts (in parts per million), introducing an approximate error of 5 per cent. in the readings, is shown in the following table, which serves to indicate the limitations of the method : Salt. Sodium sulphate, hydrated ... 500 Magnesium sulphate, hydrated.. . 1,000 Potassium acid sulphate ... 1,500 Potassium nitrate ... ... 1,000 Calcium nitrate . . . ... ... 2,000 Magnesium nitrate . . . 2,000 Sodium chloride ... 2,000 Potassium ethyl sulphate 3,000 Sodium nitrate ... ... 5,000 A. R. T. Volumetric Estimation of Phosphoric Acid and Phosphates. J. M. (Journ. SOC. Chem. Ind., 1909, 28, 68-69.)-This process is based on the Wilkie. following reactions : 1. H,P04 + 3AgN0, + 3CH3.COONa= Ag,PO, + 3NaN0, + SCH,.COOH.2. Na,HPO, + 3AgN0, + CH,.COONa = Ag3P04 + 3NaN0, + CH,.COOH. For the determination of phosphoric acid in a solution of ortho-phosphoric acid, #of, for example, 15 per cent. strength, the equivalent of 0.5 C.C. of the original acid is mixed in a stoppered cylinder with about 26 C.C. of approximately & silver nitrate solution and 25 C.C. of sodium acetate solution, the mixture diluted to 100 c.c., shaken vigorously, and the acetic acid titrated with decinormal barium hydroxide, using phenolphthalein as indicator. The end-point is sharp. A sample of phosphoric acid which was found to contain 15.17 per cent. w/v of real acid (mean result of several closely agreeing gravimetric analyses) gave 15-19 per cent. by this method.180 THE ANALYST. It is advisable to free the solution from carbon dioxide by boiling in a Jena glass- vessel for a few minutes, cooling, and using the sodium acetate solution for rinsing purposes.This precaution is essential in the case of alkali-metal phosphates. Silver phosphate is readily soluble in mineral acids and in phosphoric acid, and thus no precipitation occurs when silver nitrate is added to phosphoric acid solutions free from chloride until the free acid is largely neutralised. As an example of the use of the method for alkali-metal phosphates, 15 C.C. of a decinormal solution of crystallised disodium phosphate is boiled for five minutes in a Jeaa flask with 15 C.C. of Tv sulphuric acid. The liquid is rapidly cooled, and treated as in the case of the phosphoric acid, using 50 C.C.of Tc silver solution and 30 C.C. of After well shaking, the acetic acid is titrated as before, allowing for the sulphuric acid added. Gravimetric methods showed this sample to contain 96.84 per cent. and 96.98 per cent. of the crystallised phosphate, the volu- metric method giving 97.03 and 97.07 per cent. The method as described fails in the presence of sodium carbonate-a not unlikely impurity in these salts. To determine carbonates and phosphates, the method is carried out as described, but the titration is performed in a 150 C.C. flask. After titrating the acetic acid, 1 C.C. of normal sulphuric acid is added, the solution diluted to 150 c.c., and well mixed, filtered after standing for at least one hour, and the residual (soluble) silver determined by Volhard's process on 100 C.C.of the filtrate. The presence of alkali-metal chlorides vitiates the silver titration, but their presence is readily detected by the precipitate produced before the addition of sodium acetate in the volumetric process. If chlorides are present, they can be determined by Volhard's me hod, and a correction made. The amount of silver nitrate added in the process is immaterial, though, if added in large excess, the end-point of the titration is obscured by the precipitation of silver hydroxide. sodium acetate. The results so obtained are slightly in excess of the truth. A. R. T. Qualitative Test for Phosphoric Aeid in Roeks. A. P. Lidoff. (Zeit. anal. Chem., 1909, 48, 172-175.)-The usual method of testing for phosphorus by the blackening of silver nitrate paper is complicated by the fact that arsenic, antimony, and silicon, after treatment with magnesium, also evolve gases which blacken silver nitrate. The author, therefore, proposes to substitute cupric acetate for the silver salt.The substance to be examined is finely powdered and then ignited strongly, in order to expel water, organic matter and carbon dioxide. I t is then mixed with magnesium powder in the proportion of 80-100 mgm. of substance to 250-300 mgm. of magnesium, or a mixture of equal parts of magnesium and aluminium. The mixture is placed in an iron test-tube, loosely plugged with asbestos. The tube is then heated to a red heat until the magnesium begins to burn. When cold, a piece of wire is pushed into the fused mass and the latter is transferred to a test-tube.A 20 per cent. solution of potassium hydroxide is then added, and the tube is closed by a rubber cork which carries a, calcium chloride tube containing a cotton-wool plug, above which is a strip of test-paper. This paper is moistened with a 5 per cent. solution of cupric acetate, slightly acidified with acetic acid. The top of the tube is closed by a rubber cork, through which passes a, glass tube. The test-tube is thenTHE ANALYST, 181 warmed, and a considerable evolution of hydrogen takes place. In two or three minutes, if phosphoretted hydrogen is present in the gas, the test-paper assumes a uniform black coloration, due to the formation of copper phosphide. The liquid should not be boiled, since the condensation of water in the tube is to be avoided.After exposure to the air for five to six hours in the moist state, the black colour of the test-paper disappears either partially or completely. Arsenuretted hydrogen also blackens copper paper, but the colour has a metallic appearance quite different from that due to phosphorus; it also does not disappear on exposure to air. If ammonia be formed by the action of the alkali on the ignited mass, in quantities in excess of the acetic acid present, the test-paper becomes intensely blue in colour, and subsequently changes to brown, owing to the formation of cuproso-cupric oxide, but in this case also the original green colour is not restored under the action of moist air. J. F. B. A Mathematical View of Sampling, with Reference to the Degree of Accuracy to be obtained. M.L. Griffin. (JOZLWZ. SOC. Chenz. Id., 1909, 28, 192-194.)-The author shows that the well-known curve connecting the number of variations from a mean value with the magnitude of their departure from the mean holds for the case of a number of samples taken from the same bulk. The general law for the curve is y = Ke-h2fl, where x represents the amount of the variation from the mean, and y the number of these variations (ie., the probability of their occurrence). It follows that extreme variations from the mean are so improbable that they do not occur. I n general, the arithmetical mean of a series of observations of equal weight may be taken as the true mean, the probable error varying inversely as the square root of their number.For observations of different weights, each observation must be multiplied by its weight, and the sum of the products divided by the sum of the weights to obtain the mean. Practically, in sampling down, the number of particles present should remain constant--i.e., the smaller the sample becomes, the finer must it be crushed. A. G. L. Composition of Washing-Powders containing Sodium Peroxide. B. Pfyl. (Arbeit. Kaiserl. Geszmdheitsanzte, 1909, 30, 87-92.)-Analyses of preparations, sold under fancy names and described as (( chlorine-free bleaches,” are given. The pre- parations examined were packed in tins divided into two parts, an inner and an outer, directions being given for mixing stated quantities of the contents of the inner and outer compartments with water to prepare the bleaching solution.The contents of the inner compartment were found to consist of from 76 to 80 per cent. of sodium peroxide, 20 per cent. of calcium carbonate, and small quantities of alkali carbonate and hydroxide. The substance in the outer compartment consisted of ordinary soap- powder containing some clay and silica. Whilst the addition of the mixed powders to water, under the conditions given in the directions for using the preparations, was unaccompanied by any marked reaction, it was found that an explosive reaction could be produced by adding water, drop by drop, to the mixed powder. Two specimens of another similar preparation were found to consist, as regards the contents of the inner compartment, of from 18 to 34 per cent.of sodium peroxide182 THE ANALYST. respectively, mixed with large quantities of sodium carbonate, fat, and soap, whilst the outer compartments contained ordinary soap-powder. w. P. s. Volumetric Method for the Estimation of Titanium and of Titanium and Iron in the Presence of Each Other. E. Hibbert. (Jozcrn.. SOC. Chem. Ind., 1909, 28, 189-190.)-1n one part of a solution containing titanium and iron, the titanium is estimated, after reduction by zinc and hydrochloric acid, by titration with a solution of methylene blue, which is standardised against a standard titanium solution. I n another part of the original solution, iron (in the ferric state) is estimated by titration with titanous chloride solution. Iron salts have no action on methylene blue, but the lower oxides of vanadium and tungsten reduce it.The reduction of the titanium is conveniently carried out in a flask closed by st rubber stopper, carrying a Bunsen valve and two short glass rods. The top of the valve is closed, not by the usual glass rod, but by a short glass tube closed by s small rubber stopper. Through this rubber stopper a piece of platinum wire is inserted, the lower end of which, inside the flask, carries a small rod of zinc, which effects the reduction. When this is complete, the zinc is raised above the liquid by means of the wire, carbon dioxide is passed through the flask by removing the two small glass rods, the zinc rod is rinsed with water, and the titration effected. The maximum error of the method is about 0.3 per cent.A. G. L. Iodometric Estimation of Vanadic Acid, Chromic Acid and Iron in Presence of Each Other. G. Edgar. (Zeit. Anorg. Chenz., 1909, 61, 280-285.)- To 25 C.C. of a solution of sodium vansdate, potassium bichromate and ferric chloride, 1 to 2 grams of potassium bromide and 25 C.C. of concentrated hydrochloric acid are added, and the mixture distilled down to a volume of 25 C.C. in a current of hydrogen, The bromine evolved is absorbed in an alkaline solution of potassium iodide, which is cooled, acidified, and titrated with & sodium thiosulphate solution. The value obtained corresponds to the reduction of V,O, to V,O,, and of CrO, to Cr,O,, the iron being unaffected. The residue in the distilling bulb is then mixed with 1 grain of potassium iodide, 10 C.C. of concentrated hydrochloric acid, and 3 to 5 C.C. of syrupy phosphoric acid, and the distillation continued as before until the residue measures about 10 C.C. The iodine now liberated corresponds to the reduction of V,O, t o V,O,, and of Fe,O, to FeO. I n another 25 C.C. of the original solution, chromic acid only is estimated by acidulating with sulphuric acid, and adding 3 C.C. of syrupy phosphoric acid and an excess of & arsenious oxide solution. After stbanding for fifteen to twenty minutes, the mixture is made alkaline with sodium bicarbonate, and an exceBs of Tc iodine solution added. After standing for another thirty to sixty minutes, the excess of iodine is estimated by means of the arsenious oxide solution, starch being added as usual. From the three titration values obtained, the quantities of vanadic acid, chromic acid, and iron present can be calculated with an error of not more than a few tenths of a milligram on 0.06 to 0.20 gram of substance present. The distillations are conveniently carried out in an inclined cylindrical vessel, made from a 100 C.C. pipette by bending up both stems, the lowerTHE ANALYST. 183 one being fused to a small tap-funnel, which can be connected with a hydrogen generator, and the upper stem being expanded into a small bulb to catch spray, and then bent down again so as to dip into the absorbing liquid. A. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9093400173

出版商:RSC    

年代:1909

数据来源: RSC

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THE ANALYST. 183 APPARATUS, ETC. New Form of the Von Babo-Krafft Continuous Mercury Pump. C, Hansen. (Zeit. mzgezu. Chenz., 1909, 22, 337-338.)-The pump shown in the figure is rendered more rapid than the ordinary form by branching the mercury supply tube and providing two tubes through which the mercury drops. Each supply tube is provided with a tap. The main mercury supply tube is provided with an air-trap, consisting of a glass bulb, into which the loEer prolongation of the tube extends nearly to the centre. A valve, consisting of a glass float weighted with mercury, is provided in the tube through which the mercury is returned to the reservoir, and prevents the entry of an undue amount of air. The pump requires about 70 C.C. of mercury. ‘It is constructed by Desaga of Heidelberg, at a cost of about 100 marks.A. G. L. An Electrically Controlled Gas Regulator. E. E. Reid. (Ainer. Chem. Journ., 1909, 41, 148-152.)-A glass U-tube of about 8 mm. internal diameter is provided with a, side-tube, and is enlarged at the top to hold a small rubber stopper. Through this stopper passes the gas- delivering tube, with an external diameter 1 mm. less than the bore of the U-tube, and this tube is inserted so that its lower end is below the side-tuba. The U-tube is filled with mercury to a point a, little more than half-way up to the side-tube, .and so that there remains a space of 4 & 1 mm. between the surface of the mercury and the end ,of the gas-delivery tube. In the other arm of the U-tube a weight, of very soft iron-rod, 7 mm. diameter and 15 to 20 mm.long, is suspended freely from a hook on the armature of an electro-magnet, and the iron rod acts simply by its weight on the mercury. The armature is held up by a spring which is fastened rigidly at its other end, and this spring is adjusted to support the weight, but to yield quickly to the magnet, If the sudden motion be rigidly and suddenly transmitted to the mercury, the latter may splash into the side-tube. The gas enters by the above-mentioned delivery-tube, and flows under the lower end of the tube, up through the space between the tubes, and out at the side-tube. When the electro-magnet is actuated, the lowering of the iron weight causes a, corresponding elevation of the mercury in the other arm, partially or wholly closing184 THE ANALYST. the space between the bottom of the delivery-tube and the surface of the mercury, and so shutting off the gas.The delivery-tube is provided with a pinhole opposite the side-tube, through which sufficient gas passes to the burner to keep it lit. I n constructing the apparatus, two or three very small pinholes may be made, and closed with wax. One or more of these, as the size of the burner may require, can be opened with a hot needle to allow the passage of gas for a pilot flame, or the burner may be provided with an independent supply to maintain a small flame. For the electro-magnet an ordinary electric bell may be used, the vibratory make-and-break being short-circuited and the bell removed. The magnet may be wound up to 20 ohms to economise current.With this resistance, a single storage cell will give good results, while with less resistance an ordinary dry cell suffices. Instead of being suspended, the weight may be floated on the mercury, the amount of the latter being adjusted to allow of the proper passage of the gas. In this case the electro-magnet is dispensed with, and a coil of wire wound round the limb of the U-tube containing the weight. The resistance of the coil should be between 5 and 20 ohms, according to the battery used, and the coil should be placed somewhat below the centre of the weight. When the current is passed, the weight is drawn down and the gas-supply cut off as before. The apparatus may be con- trolled by an electrical regulator, by which a contact is made when a certain tem- perature is exceeded, and broken when the temperature falls.A modified form of this regulator, in which the whole apparatus is encased in a block of cast iron, is recommended on the score of compactness and safety. A. R. T. A New Automatic Ureometer. E. Pozzi-Eseot. (Ann. Chinz. anal., 1909, 14, 52-53.)-The author describes a new ureometer flask which obviates the incon- venience of measuring out each time the necessary quantity of hypobromite solution. The apparatus (see figure) consists of a reaction-flask, A, of suitable size, with a wide neck. Into this neck is ground a stopper, B, carrying three tubes. C is the gas-evolution tube, connected with the gas burette; D is a dropping-tube fitted with a tap, and con- nected with the cylindrical funnel R, containing the hypobromite solution; E is a tube connecting the flask A with the upper part of the funnel R, enabling the liquid to run easily from the one vessel to the other.The funnel R is closed by a stopper, M, through which communication can be made with the outside air when necessary. The whole apparatus measures 120 to 150 mm. in height; the capacity of A is 30 to 60 c.c., and that of R, 20 to 30 C.C. When in use a measured quantity of urine is placed in the flask A, and an excess of hypobromite in the funnel R ; the pressure is adjusted, and, the apparatus being closed, a measured quantity of hypobromite solution is allowed to pass through the stopcock D. The apparatus is, of course, applicable to the analysis of many other substances by the gas-evolution method.J. F. B.THE ANALYST. Apparatus for the Examination of Flour. suclz. Nahr. Gewssm., 1909, 17, 86-88.)-The apparatus figures; the ends of the central glass rod are so shaped that they may be used as stoppers for the upper and middle parts of the apparatus respectively. About 30 grams of the flour to be tested are placed in the apparatus, the lower end having been closed with a rubber stopper, and the lower bulb is about one- third filled with chloroform. The glass stopper is inserted, as shown in Fig. A, and the contents are well shaken; the stopper is then raised, and the apparatus is filled with chloroform almost up to the edge of the upper funnel-shaped bulb. The latter is then covered with a glass plate, and the apparatus is set aside for a time. Fragments of husk, hair, and other impurities rise to the surface of the chloroform, and, after the stopper has been inserted in the upper part, may be decanted into a beaker for further examination.The remaining contents of the ap- paratus, after a further period of about twenty-four hours, will be found to have separated into a thick emulsion which fills the bulb, whilst below this, and in the neck of the apparatus, is a layer of 185 E. Schaffnit. (Zeit. Untev- is shown in the accompanying A B chloroform having a more or less yellowish colour. At the bottom of the neck will be found a yellow precipitate (gluten cells). By inserting the stopper, as shown at Fig. B, these layers may be separated from one another. The apparatus is also useful for the detection and separation of mineral adulterants in flour ; these settle rapidly to the bottom of the neck, and may be removed by opening the rubber stopper.w. P. s. A New Potash Absorption Apparatus. M. S. Losanitsch. (Re?.. deut. Chenz. Ges., 1909, 42, 237-238.)-An improved modi- fication of the well-known Geiesler potash bulb is shown in the figure. The entry-tube x is fused into the neck of the bottle E, which is filled with glass-wool and the series of three potash bulbs, w. The exit from the bottle H communicates with the ball K, and this in turn communicates, by way of the hooked shaped tube h, with the vertical tower R, whence the gas escapes through a. In order to charge the apparatus, the potash solution is sucked through z into the bottle H, and is then drawn through the tube r into the three bulbs 20, in which it is uniformly distributed.The tower 11 is plugged at the bottom with glass-wool, and then charged either with ignited, sifted soda-lime or with potassium hydroxide and calcium chloride in the usual manner, and a plug of glass- wool is placed before the exit. The whole apparatus weighs about 25 grams186 THE ANALYST. empty, and 50 to 60 grams charged; it is self-contained, and all joints, with the exception of the stopper, are fused; it is stable, and can easily be wiped before weighing. The main bulk of the absorption takes place in the bottle H, in which a large surface of potash solution is exposed to the gas by the glass-wool with which it is packed. As in all apparatus of this class, it is neceesary to attach a guard-tube at the exit to retain any moisture carried through by the current of gas; the hooked shape of the narrow tube h, however, reduces the loss of moisture to a minimum.J. F. B. Apparatus for the Purifieation of Mercury. L. J. Desha. (Amer. Chem. Joum, 1909, 41, 152-155.)-The figure shows an automatic apparatus for the purification of mercury, which is continuous in its action and can be used for large or small quantities. A and B are tubes, 22 mm. in diameter and 90 cm. and 35 cm. in length respectively, connected at their lower ends to a U-shaped tube carrying a stopcock, M. C is a thick-walled glass tube, 1.5 mm. in bore and about 200 om. long, and to which a side-tube with stopcock is fused just above B. I t s lower end hangs loosely in B near the constriction, and the upper end passes through the rubber stopper D into E, which latter is 20 mm.wide and 15 cm. long, and terminates in the thick-walled capillary F, 76 cm. long, extending to the bottom of the mercury-trap, G. The capillary-tube H is fused into G ; its upper end is expanded and extends 25 mm. above the outlet of F, while its lower end, extending 10 cm. into the liquid in A, is blown into EL small bulb containing several very small holes. A second tube leads from E through D to the suction-pump. Mercury is poured into A or B in any desired qutntity, but at least sufficient to cover the end of the tube C in B. A is next filled with 1 per cent. nitric acid or other purifying solution. The trap G is filled with mercury to the level of the t > p of the tube H, and the suction-pump started.Under the diininished pressure produced in C and E mercury is drawn from € into C, and the stopcock L is so adjusted that alternate small irortions of mercury and air are drawn into E. Mercury is also simul- taneously drawn from G into F until the pressure in F a~ d C is equalised. The mercury coming from C into E runs do-n the a tube F into G, then into H, and is finally discharged through the minute openings in the bulb into the cleansing solution in A. The purified mercury is withdrawn at M. By adjustment of the stopcock L the maximum efficiency for any giveu pump may readily be ascertained. The aut.ior proposes to further increase the efficiency of the apparatus by combining an electrolytic cleansing action with the abo 'e I automatic principle. To effect this, a platinum plate will be hung in A beside tl e bulb of E, and surrounded by a silk bag, and a small platinum wire will make th? electrical connection with the mercury in H (the anode). A small current passec'THE ANALYST. 187 between it and the platinum plate in the nitric acid will serve to electrolyse out the impurities in the charged small globules of mercury issuing from H, and the bag will prevent any deposit on the cathode from again contaminating the mercury. A. R. 2’.

ISSN:0003-2654    

DOI:10.1039/AN9093400183

出版商:RSC    

年代:1909

数据来源: RSC

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THE ANALYST. 187 T H E I N S T I T U T E OF CHEMISTRY. THIRTY -FIRST ANNUAL GENERAL MEETING. THE thirty-first Annual General Meeting of the Institute of Chemistry was held at 30, Bloomsbury Square, London, W.C., on Monday, March 1, at 4.30 p.m,, Professor Percy F. Frankland, the retiring President, in the chair. The annual accounts were received, and the EON. TREASUREE said that, regarded a8 a business concern, the position of the Institute was sound for its present needs. It was paying its way and putting a little by, but it had not sufficient to meet the problem of the future-namely, the approaching expiry of the lease of its premises. During the year 1908, however, the improvement in the finances of the Institute had been more than fully maintained. Professor PERCY F.FRANKLAND, the retiring President, then delivered his address. Whilst he regretted that the honour of representing the Institute had drawn to a close, it was by no means disagreeable to leave the responsibilities which the office of President involved. He was very thankful that, through good fortune and the help of the councils and officers with whom he had been associated, he was able to hand over the affairs of the Institute in as sound and healthy a condition as when he took them over from his predecessor three years ago. The roll of the Institute has increased by 78 Fellows, 30 Associates, and 68 Students; and, not- withstanding the increasing stringency of the regulations, the number of candidates for examination had increased from 94 (in 1906) to 150 (in 1909). He believed these figures indicated that a real advance was taking place in the demand for highly trained chemists.He would emphasise the fact that whilst the well-being of the community was greatly promoted by the services of competent chemists, the mischief which could be wrought by the ill-trained and incompetent was incalculable. It was one of the chief duties of the Institute to maintain a high level of training for professional chemists, by demanding of candidates for its membership evidence of thorough training, and by requiring them to pass searching examinations. Par- ticular attention had lately been given to the educational side of the Institute’s activity, and he referred to five important changes : Latin, hitherto compulsory, had been transferred to the list of optional subjects in the preliminary examination ; the number of examiners had been greatly increased, forming a Board the members of which were jointly responsible for the examinations ; written papers had been introduced in the final examination; a working knowledge of French and German would shortly be required of all candidates for the final examination; and the Council now encouraged the holding of examinations in India, in the Colonies, and in different centres of the United Kingdom.There was no finality either in the188 THE ANALYST, syllabus of the examinations or in the courses of training demanded. Such arrange- ments would require frequent remodelling in the future as the development of science and improvement of facilities of higher training might dictate and render possible.The PRESIDENT then referred to the criticism of the Institute by Professor Kipping in his presidential address to the Chemical Section of the British Associa- tions at their meeting last year, wherein he indicated that the Institute ignored the necessity of research work, and suggested that good research work should be insisted on in the caBe of all candidates for its fellowship. Professor FRANKLAND reminded the Fellows that the results of research were not necessarily recorded in the Transactions or Proceedings of the Royal Society or in the pages of any scientific journal ; those were mostly for academic researches. There waB a vast amount of research involving originality and attainments of the highest order which from its very nature could not be published at all.Should chemists who are engaged on such research be debarred from the Fellowship because their names are not at the head of so many dozen pages apiece of the journal of the Chemical Society or in a similar publication? He would assure Dr. Kipping that he had met chemists whose names are not associated with such academic researches who were nevertheless fully equipped and highly original investigators. Should these men not have been admitted to the Fellowship of the Institute? Succeeding Councils had built up an organisation of real flesh and blood, and not a paper Utopia. Could anybody deny that the Institute had by its policy during the thirty-two years of its existence enormously improved the theoretical and practical equipment of professional chemists in this country, and that it had stimulated hundreds to pursue courses of study which but for the Institute would never have been undertaken at all? Could it be denied that the examinations were specially distinguished as tests of original capacity as well as of theoretical attainments, manipulative skill, and knowledge of routine methods ? Noreover, the examiners were empowered to take into consideration any research work which any candidate might previously have carried out.He mould yield to none in the advocacy of research as a part of training, but one must not be misled by an empty phrase or mere nomenclature. There was much training in originality of thought and experimental procedure which was not called research, and much of what was called research that involved no originality in the thought or deed.The PRESIDENT then referred to the work of the various committees, indicating how the Institute had endeavoured to promote the interests of its members. He made special reference to protests made by the Council against professional chemists being invited to apply for appointments by tender, and appealed to the Fellows and Associates to assist in the endeavour to crush this sinister development, The Institute had lately taken steps to establish an Appointments Register, and had already succeeded in placing a number of members in good positions. Steps would be taken to make manufacturers and other employers aware of the existence of this register, which promised to be most useful.Passing to the most important item in his address, the President intimated that a special committee had been discussing the arrangements to be made in view of the approaching expiry of the lease of the present premises of the Institute.THE ANALYST. 189 The committee had come to the conclusion that between $10,000 and 615,000 would have to be raised by voluntary contributions, in order to provide even a modest, but dignified home, in which the Institute could carry on its administrative work and conduct its examinations. They did not require a pretentious exterior or luxurious interior, but they wanted more commodious laboratories, offices, and library. The sum named left no margin for extravagance. The committee had prepared a pamphlet, setting forth the work of the Institute, discussing its present and prospective financial position, and giving a clear account of the aims in view, and the President urged the Fellows and Associates to read it carefully, after which they would, he felt sure, make such contributions as they could afford.Their joint action and personal sacrifice would continue to bear fruit in the time which is to come long after they had become sleeping and forgotten members of that professional brotherhood in which it was their privilege now to be active workers. The officers and members of Council for the ensuing year were duly elected as follows : Presideizt.-George Thomas Beilby, LL.D., F.R. S. ~ice-Pi,esideitts.-Bernard Dyer, D.Sc. ; Martin Onslow Forster, D.Sc., F.R.S. ; Percy Faraday Frankland, LL.D., Ph.D., F.R.S. ; Oscar Guttman, M.1nst.C.E. ; Egbert Grant Hooper ; Raphael Meldola, F.R. S. Hen,. Tyeaszwer.-Alfred Gordon Salamon, A.R.S.M. Members of CozmciZ.-Leonard Archbutt ; William John Atkinson Butterfield, M.A. ; Russell Forbes Carpenter ; Francis Howard Carr ; Charles Edward Cassal, Colonel, V.D. ; Alfred Chaston Chapman ; Frederick Daniel Chattaway, U.A., D.Sc., F.R.S. ; Arthur Crozier Claudet, A.R.S.M. ; Harold Govett Colman, M.Sc., Ph.D. ; John Henry Coste ; Arthur William Crossley, D.Sc., F.R.S. ; Walter William Fisher, M.A. ; Walter Charles Haucock, B.A. ; Otto Hehner ; George Gerald Henderson, M.A., D.Sc. ; William Richard Eaton Hodgkinson, Ph.D. ; Frederick Gowland Hopkins, M.A., M.B., D.Sc., F.R.S. ; William Macnab ; George McGowan, Ph.D. j Gerald Tattersall Moody, D.Sc. ; Kennedy Joseph Previt6 Orton, M.A., Ph.D. ; William Jackson Pope, M.A., M.Sc., F.R.S. ; Robert Rattray Tatlock ; Oliver Trigger ; John Augustus Voelcker, M.A., B.Sc., Ph.D. ; Alexander Forbes Watson, B.Sc. ; William Maurice Gathorne Young.

ISSN:0003-2654    

DOI:10.1039/AN9093400187

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

190 THE ANALYST. REVIEWS. A TREATISE ON COLOUR MANUFACTURE. By GEORGE ZERR and R. RUBENCAMP. English Edition by C. MAYER. 1908. Pp. xiii x 605. 30s. net. London : E. C. Griffin and Co. This work is a comprehensive treatise on the manufacture of the most important pigment colours in use at the present time. The introductory chapter deals with the authors’ classification of pigments, and also contains a short summary of a few fundamental principles required for the proper understanding of the succeeding sections. Under the heading of ‘‘ Artificial Mineral Colours ” the authors give a detailed description of the plant required in the compounding, moulding, drying, crushing, and grinding of these pigments. Dealing next with the actual manufacture of the artificial mineral colours, reference is made not only to the old-established products, but also to such recent introductions as lithopone and zinc yellow, which have been successfully employed as substitutes for the deleterious lead pigments.The modern processes for the production of ultramarine are also described. The analytical side of the manufacture of these colours is not entirely neglected. The simpler qualitative tests for the purity of the raw materials of the mineral colour industry are indicated, and in some cases quantitative methods of evaluation are suggested. Several useful tabulations are given of the principal mineral colours and of the materials employed in the production of lakes. The treatment of the natural mineral colours is dealt with in a special section, and another chapter is devoted to an account of the manufacture of lampblack and allied pigments.One of the most interesting portions of the book is that dealing with the application of the coal-tar colours in the production of lakes, for it is in this direction that progress has recently been most rapid. The general nature of lakes is discussed, and the formation of these pigments from various classes of synthetical colouring matters is illustrated by many typical examples. The concluding chapter refers to the application of the pigment colours in the arts of painting and dyeing. The treatise is illustrated throughout, and cannot fail to be of service to those wishing to gain aninsight into this important branch of applied chemistry. G. T. MORUAN. THE CHEMISTRY OF ESSENTIAL OILS AND ARTIFICIAL PERFUMES.By ERNEST J . PARRY. 1908. Price 12s. 6d. London : Scott, Greenwood and Son. Mr. Parry’s book presents within a reasonable compass a very large amount of judiciously-selected and well-arranged information of just the kind which the analyst who is interested in this branch of the science requires. The developments during recent years in the essential oil and artificial perfume industries, and the additionsTHE ANALYST. 191 made to our knowledge of this fascinating department of chemistry, have been so considerable, that the enlargement and revision of the first edition, published in 1899, had become almost a necessity. The author of a work dealing with the chemistry of the essential oils is confronted at the outset with a problem of some difficulty-that of deciding upon the class of reader to whom he intends particularly to appeal, and of determining how much and what ground he should cover. Thus, the chemical and physical properties of the compounds occurring in the essential oils are fully described in numerous treatises of general organic chemistry, and in certain special works such as that of Heusler, so that more than a brief review of this portion of the subject is unnecessary.Again, the work is either to constitute a laboratory textbook for the inexperienced analyst, in which case questions of analytical procedure must be dealt with in detail, or it is intended for the experienced worker, in which case very much may be taken for granted. In the work under review the author has wisely devoted by far the larger portion of his space to a systematic consideration of the natural history of the essential oils, and has condensed those portions dealing with descriptive organic chemistry and methods of analysis within a comparat.ively small compass.Perhaps this process of condensation might have been carried still farther without detracting from the value of the book. A work such as this is clearly intended for the specialist, or, at least, for the experienced analyst, and, consequently, it does not appear to be really necessary to describe the operations involved in determining specific gravities by means of a bottle or a Sprengel tube, or to devote space to a description of the polarimeter, the Abb6 refractometer, or any other of the common appliances of a well-equipped laboratory.The author has very properly classified the various oils according to the botanical relationships of the plants producing them, and the subject matter is accurate, and, with it few exceptions, in accordance with the most recent knowledge. I n a few cases, however, the author does not appear to have referred to the latest memoirs, and in some instances the information given might have been amplified with advantage. Thus, no reference is made to hop oil as a source of myrcene (p. 32), although it contains from 25 to 30 per cent. of that hydrocarbon ; and more space might have been devoted to Java citronella, oil, the numbers given as typical for that oil being, in the writer’s experience, far from characteristic.In reference to the chapter dealing with analytical matters there is nothing that calls for special remark, save, perhaps, that, in speaking of Valenta’s dimethyl sulphate method, Borne referenc might well have been made to the recent experimental revision and criticism of the work by Harrison and Perkin (ANALYST, 1908, 33, 2). Among the minor blemishes may be mentioned the use of such expressions as in vacuo for ‘‘ under reduced pressure,” “ points ” (p. 103) for ‘‘ units,” “ferment ’’ for (( enzyme,” and a tendency to refer to the month of publication of certain journals instead of to the pages (see pp. 131 and 132). The book includes in the form of an appendix a list of the requirements of the principal pharmacopoeias in respect of such essential oils as are included in them, information which is not always easily obtainable, and which will be of use to a good many readers. The printing is good, the illustrations clear, and there is an adequate index.192 THE ANALYST. Mr. Parry has produced a good book, and one which cannot fail to be of considerable usefulness t o all who axe actively interested in the chemistry of essential oils and synthetical perfumes. A. C. CHAPMAN.

ISSN:0003-2654    

DOI:10.1039/AN9093400190

出版商:RSC    

年代:1909

数据来源: RSC