摘要:

THE ANALYST. JANUARY, 1888. PROCEEDINGS OF SOCIETY OF PUBLIC ANALYSTS. AN ordinary meeting of this Society was held on the 14th ult. at Burlington House, the President, Mr. A. H. Allen, in the chair. The minutes of the previous meeting were read and confirmed. On the ballot papers being opened it was reported that the following gentlemen had been elected :-As member, W. Hogben, analytical chemist. As associate, A. W. Trench, assistant to Mr. 0. C. Hagemann. The following gentlemen were proposed for election :-As members, John Heron, analytical chemist ; W. E. Matthews, analytical chemist, of Melbourne ; Laurence Briant, brewer’s analyst, Holborn Viaduct. Mr. Fox was appointed auditor for the ensuing year, and in case Mr, Johnstone continued too unwell to act, it was decided to ask Mr.Harland to assist Mr. Johnstone. Mr. Adams proposed, and Mr. Hehner seconded, a notice of motion, to be on the agenda for next meeting, that ‘‘ Mr. W. F. Lowe, of 13, Cheapside, be appointed Solicitor to the Society, and that whenever legal business is likely to come before the Council he be requested to attend.” The following papers were read and discussed :- ‘‘ Note on the Estimation of Peroxide of Hydrogen.” ‘‘ The Relation between Specific Gravity, Fat and Solids not Fat, upon the Basis of the Society’s Process for Milk Analysis.” By Otto Hehner and Henry D. Richmond, At the instenco of Dr. Muter (who was absent through illness), Mr. Hehner referred to the new Margarine Act, which comes into force on the 1st of January, and to the question of public analyste’ certificates under it. By C. T. Kingrett2 THE ANALYST. ~~~ After some discussion it was ultimately decided that if proceedings were being taken under the new Act, the best form of certificate would be, I am of opinion that this is a sample of margarine,” without stating the relative quantities of butter and foreign fat ; and, if under the Sale of Food Act, the quantities must be given as hitherto. The Annual Meeting will take place on the 11th of January inst., after which the usual dinner will be held, of which due notice will be given.

ISSN:0003-2654    

DOI:10.1039/AN888130001b

出版商:RSC    

年代:1888

数据来源: RSC

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2 THE ANALYST. ON FILTRATION. BY OTTO HEHNER AND HENRY D. RICHMOND. IZead at Meeting, November, 1887. CONSIDERING that a large percentage of the analyst’s working time is spent upon various filtering operations, it is not a little remarkable how ill the conditions are understood which influence the rate at which a fluid passes through a filter. The text-books are generally silent upon the subject, or, when they do give instructions to the student, mostly direct that the filter-paper should be fitted into the funnel as closely as possible. (See, for instance, Fresenius’s (‘ Qual. and Quant. Analysis.”) I n many laboratories where students are instructed, this advice is followed. In others the paper is folded so that the angle formed by the edges of the filter should meet in an angle somewhat larger than 90”.In others, again, various forms of pleating the filters are in use. If we except the Bunsen Waterpump arrangement-which no doubt allows of the most rapid working, but is not in general favour owing to the transferring of filtrates from one vessel into another which it entails, and the not infrequent breaking of filters in the middle of an analysis which occurs,-for quantitative purposes, smooth filters closely fitted, or loosely laid into the funnel, are employed ; for qualitative work, various forms of pleated filters, It has long ago been observed by Fleitmann (“Zeitsch.f.Ana1. Chem.,” xiv.,p. 77) that in many cases a double filter filters more rapidly than a single one, because it presents a thicker passage for the filtrate to escape, With a similar intention, Ebermayr ( ‘ I Chem.Centralbl.,” 3, f. x., 176) recommends to lay under the filter a small piece of muslin into the funnel. Hempel (‘‘ Zeitsch. f, Anal, Chem.,” xiv., p. 308) etches, with hydrofluoric acid, a few channels into the funnels used in connection with a Bunsen pump, whilst De Mollins (“Zeitsch, Anal. Chem.,” xix., p. 334) uses a perforated cone placed into a funnel. A similar arrangement has recently been patented in England by Nickels. When a filter-paper of sufficient coherency is placed tightly into a funnel in the manner directed by Fresenius, and the rate of filtration ascertained, and the paper, when empty, is then cautiously lifted so that a glass rod may be placed between it and the funnel, the velocity of filtration is in,all cases much increased.It is evident that by placing the paper close to the walls of the funnel the fluid which is capable of passing through theTI€E ANALYST. 3 pores of the paper cannot find an exit with sufficient rapidity to allow of the total filter- ing capacity of the paper being brought into play. The smoother the funnel and the more nearly its angle approaches GOO, the more complete the fit and the greater the blockage. The old-fashioned fluted funnels were no doubt constructed to counteract this blockage, but in the case of the thin filter-paper now generally in use, this object is not attained, the fluting being too shallow to prevent the paper, expanded as it is by the moistening, from clinging closely to the funnel and barring the flow of ths filtrate.We therefore got some funnels made which have a number, generally four, high ridges running straight on the inner surface from the edge of the funnel for some dis- tance into ths shaft. It is impossible for the filter-paper, however thin, to adapt itself to the sides and to obstruct the flow of the filtrate, whilst a t the same time sufficient support is given to the paper t o enable it to bear the heaviest precipitates without risk of breakage. The following table gives the time, in seconds, required for filtering 250 C.C. of cold water. I n all cases the filters mere kept full of water during the duration of the experiment. For the purpose of strict comparison, we attempted to use one and the same piece of filter-paper for the different modes of filtration, but we found that even pure water gradually blocks up or contracts the pores of the paper, each succeeding litrs requiring a somewhat longer time than the preceding one, as will be seen from the following set of figures, which represent such successive times :- 217, 345, 267, 282, 293, 295, 296 seconds.For cadi experiment, therefore, ,z new piece of paper was taken, all from the same bundle, and four separate sets of trittls were made to equalise as much as possible differences in thickness and porosity. Column 1 shows the kind of filter-paper used; 2, the rate of filtration in the case of the old smooth funnel with narrow shaft, the paper laid closeIy into the funnel, and the shaft kept full of water; 3, filtration fhrough smooth funnel, with shaft cut short, the paper being folded 5 3 as not to fit well; 4, new funnel with four high ridges, paper dropped in anyhow; 5, old fluted funnel, no par- ticular care taken t o fit the paper ; 6, pleated paper for qualitative analysis; 7, paper pleated in the following manner, and shown in the figure :-Fold the paper across the centre as usual, open it, and fold it again at right angles; press the parts be tween the diameters thus indicated inward to the middle; the paper when looked a t from the top now forms a four-pointed star.Press it flat; the outer edges now meet at an angle of 90" Double back each pair of edges, so that they meet in the middle, n:ld open the filter as shown in the figure. All papers were of the same size.4 TI-IE ANALYST.1 2 3 4 5 6 Smooth ; Folded larger New Old Fluted Pleated "per' Shaft full. than 90°. Funnel. Funnel. Paper. 682 Best Swedish,j 200 Thin . .. . I 480 I- 218 Average 395 ( 328 -- 306 English, Thin< 156 c 181 -- Average 285 Schleicherand ( 563 S~hG11(590),( 450 washedwith I 545 H.FI. . . .. 750 Average 577 -- (1070 Schleicherand I 700 SchGll(59 7), -( very Thick c 6o -.- Average 886 Schleicherand I 412 SchB11(597),-( 388 Thick .. . . 430 (- 54s -- Average 445 592 5 48 138 85 341 137 135 79 287 160 840 160 180 950 357 415 368 1125 280 547 517 182 252 252 30 1 -- -- -- -- -- 95 95 97 74 90 51 60 49 65 56 160 145 192 162 165 262 350 332 322 317 188 212 168 160 182 - - -- -- -- 854 1290 600 115 715 152 90 217 152 153 338 543 582 508 492 295 288 420 488 3 73 132 455 188 507 321 -- -- -I -- -- 56 70 61 84 68 52 45 80 48 61 98 100 90 188 119 192 210 180 202 198 85 88 135 80 97 - - I- - 7 Richmond's Pleat.70 73 69 60 68 75 83 91 55 76 120 200 155 150 156 155 172 175 160 150 92 100 145 92 107 - - -- -- -- It is seen that, with all classes of filter-paper examined, the worst plan which can be adopted is to fit a filter closely into the funnel. The paper does not get a chance to work, and the loss of time is very great, the greater the thinner the paper. When the filter is folded so that it lies loosely in the funnel, excellent results are frequently ob- tained, but these are somewhat erratic, especially with thin papers, because the paper is apt to slip closely into the funnel when fully weighted with water. In all cases the velocity in Class 3 was tbe greater, the greater the angle a t which the fold was made.It disposes of any chances due t o imperfect folding or fitting of the paper ; it allows more freely than any of the other methods the passage of the fluid into the stom, and this far more cer- tainly than the old fluted funnel, which, indeed, with thin paper gives very bad results. Paper folded in pleats in the usual manner filters, especially in the case of very thick paper, faster than smooth filters are capable of doing, but the long, uneven The new ridged funnel gave the best and most concordant results.THE ANALYST. 5 edge renders washing so diflticult that they cannot well be used for exact quantitative work. The folding used in the tests stated in Column 7 is intended t o obviate this diffi- culty as far as possible, and to provide a pleated filter with a smooth edge. It will be seen that its filtration velocity equals that of ordinary pleated paper. The funnels with deep ridges, described in this paper, have been made by, and may be obtained from Messrs. Townson and Mercer, 87, Bishopsgate Street, at a price differing but very little from that of ordinary smooth funnels.

ISSN:0003-2654    

DOI:10.1039/AN8881300002

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

THE ANALYST. 5 ALUMINA AS A NATURAL CONSTITUENT OF WHEAT FLOUR. BY W. C. YOUNG, F.C.S. (Read at Meeting, Nouember, 1887.) IN a paper read before the Society last June, and published in the August number of the ANALYST, I gave an acconnt of some experiments with the logwood test, the results of which seemed to indicate that alumina was a natural constituent of wheat flour, and, further, that it was confined to ths gluten, the starch being quite free from it. I n the discussion which followed, our President pointed out that it was generally supposed that alumina was not a natural constituent of wheat flour, and that when found it was ascribed to accidental impurities or purposely added alum. I find also that in the dis- cussion of a paper by Wanklyn at the first meeting of this Society, Mr.Allen similarly expressed himself, but Dr. Dupr6 mentioned that in conjunction with Dr. Odling he had made many analyses of wheat, and had found minute quantities of alumina in every sample. Recently Yoshida has communicated a paper to the Chemical Society on ‘‘ Aluminium in the ashes of flowering plants,” in which he shows that alumina iS a normal con- stituent of wheat and other cereals. Soon after the reading of my last paper, 1 made a quantitative experiment on wheat flour, the result of which not only confirms Yoshida’s work, but shows further that the whole of the alumina is contained in the gluten. The flour used was the best quality Vienna, containing -7 per cent. of ash, and a3 near as I could ascertain about 8 per cent. of gluten. I obtained from 100 grammes of this flour, by a process I shall presently describe, 90075 gramme of phosphate of alumina, The gluten was separated by washing in a muslin bag in the usual way, and when dried contained 1.26 per cent.ash; 20 grammes of this dried gluten, finely powdered, was then treated with about 250 C.C. of a mixture of equal volumes of acetic acid and water, and heated in the water bath for about twenty-eight hours. By this time the mass had become quite liquid, the gluten having lost its firmness in the same way that gelatin does under similar circumstances. After standing a short time the liquid was poured off, and the sediment further treated with weak acetic acid twice, and the three portions of liquid evaporated t o dryness, the sediment being rejected. I n this way I think that any extraneous earthy matter present in the gluten was separated, and, there- fore, only the natural alumina retained, The dried residue was then burnt to a perfect ash, the ash dissolved in dilute6 THE ANALYST.hydrochloric acid and filtered, the insoluble matter being well washed and weighed. The insoluble matter thus obtained weighed only -009 gramme, and of this -0075 was silica. The insoluble matter was then fused with about twice its bulk of mixed alkaline carbonates, dissolved in dilute hydrochloric acid and filtered. This filtrate was added to the acid solution of the ash, evaporated to dryness, redissolved in a small quantity of dilute hydrochloric acid and filtered. The filtrate was then boiled, and cautiously added to 25 C.C.of a saturated solution of pure caustic soda, also boiling, and the whole kept boiling for a few minutes. It, was then filtered, and the precipitate washed, the filtrate made slightly acid with hydrochloric acid, about 6 C.C. of a saturated solution of sodium phosphate added, and finally a slight excess of ammonia. After boiling for about ten miiiutes, the precipitate of phosphate of alumina was collected and weighed. I may mention that the process I have just described has been in use for some years now in my laboratory for determining alumina in bread and flour, and is really an improvement on a modification of Normandy’s old process which I suggested some years back. The points to be observed as essential to success are, first, the fusion with alkaline carbonates of the ash insoluble in hydrochloric acid, as I have repeatedly found that hydrochloric acid does not dissolve the whole of the alumina in the ash; second, keeping the solutions down to the smallest possible bulk; and third, the employment of B saturated solution of soda.I n this way I obtained ~0185 gramme of phosphate of alumina from 20 grammes of gluten. Now as the flour contained S per cent, of gluten, and gave originally *0075 per cent. of phosphate of alumina, 20 grammes of gluten would be equivalent to 250 of flour, which would yield .01S75 of phosphate of alumina. So that practically I obtained the whole of the alumina of the flour in the gluten. As in the process of washing the starch from the gluten a large proportion of any foreign earthy matter that may have been present must have been separated, and any remaining eliminated by dissolving the gluten in acetic acid, there can be no doubt that the alumina obtained in this experiment was present as a natural constituent of the flour, and I think further that the interest- ing fact is established that the bulk of it is associated with the gluten.

ISSN:0003-2654    

DOI:10.1039/AN8881300005

出版商:RSC    

年代:1888

数据来源: RSC

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6 THE ANALYST. DOES NEUTRAL OR 8lJBaACETATE OF LEAD PRECIPITATE HOP- BITTERS ? BY DR. W. JOHNSTONE. (Recut? at Heeting, November, 1887.) GENTLEMEN, It will be in your recollection that; our worthy President read a paper before the Society in May last, entitled 6 g An Improved method of Detecting Quassia and certain other Hop-substitutes in Beer,” wherein the following sentence appeared : “ Seeing that the bitter principles of hops are entirely precipitated by neutral acetate of lead, the presence of some hop-substitute is absolutely certain if the chloroform or ether residue has a marked bitter taste.” I n the interesting discussion following the mading of thatTHE ANALYST. h paper, Mr. Adams said he had no difficidty in distinguishing between a bitter of hops and the substitute used for it, but he did not think there was any possibility of distinguish- ing between the individual bitters, and one could only positively say there was another bitter present besides that of hops.Dr. Muter, in following Mr. Adams, remarked as follows: ‘ I Now came a difficulty which shook his faith as an analyst as regarded hop bitters. €10 had always believed in the process, from practising upon beers with various added bitters, until some time ago he got a beer which he was privately assured by the maker to have no bitter other than hops. This sample he put through the process, and he got a bitter out of that beer with chloroform, after using lead. Me worked on a fairly large quantity, but the process here showed bitters other than hop, although he mas assured that the sample represented as pure a beer as could possibly be obtained.” I, Mr.President, have experienced and obtained the same results as Dr. Muter, and have now no hesitation in stating that the use of neutral or sub-acetate of lead in precipitating hop bitters is no use whatever, and for the following reasons : in that I received a sample of beer from my friend, Mr. Quartermain, who assured me that it was brewed by himself, and from nothing but pure malt and hops. Now this sample of beer when put through the process gave a decided bitter. The result aroused my suspicions, and I wrote to my friend reporting the result, when he kindly replied, assuring me again that the beer was as he represented, and that there were four different samples of hops used in the brew, three of which he sent me, at the same time stating that he was very sorry he could not send the fourth sample, as they had been entirely used up a t that particular brewing, a circumstance I also regretted ; however, I submitted the three samples I received to the process and found all of them give a distinct bitter, so under these circumstances tho bitter found in the beer could not be wholly derived from the missing sample, and therefore does not affect the finding of the bitter in this particular sample of beer.The idea now occurred to me, could the three samples of hops examined have been treated in any way with an infusion of Quassia or other foreign bitter ; so to decide this question, if possible, I obtained from Mr. Spriggs, who resides at Maidstone (brother of one of my assistants), a sample of this year’s hops, plucked by himself and forwarded direct to me in the condition in which they were picked, and upon arrival they were carefully wind-dried, and then submitted to the process.The results obtained being a decided and distinct bitter. This morning I received a sample of hops from our President, who, in the letter that accompanied the sample, informed me that he could obtain no bitter from them after having submitted them to the process. I, fortu- nately, have been able‘also to pass them through the mill, but with quite a different result. Here, gentlemen, is the bitter extracted for you to taste. I shall not detain you any longer, gentlemen, but conclude by stating that the process described by our President in his paper, read before the Society and published in the June number of THE ANALYST, is quite misleading, and that the use of neutral or sub-acetate of lead, used in the manner as therein described, does not precipitate the natural bitter belonging to hops. ( Cone ZICS ion of the ,Socie~yl’s I’mxwZin gs. ) One fact more, and I am finished.

ISSN:0003-2654    

DOI:10.1039/AN8881300006

出版商:RSC    

年代:1888

数据来源: RSC

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8 THE ANALYST. ON REICHERT-MEISSL’S METHOD OF BUTTER ANALYSIS, AND ITS APPLICATION FOR THE EXAMINATION OF BUTTER AND BUTTER SUBSTITUTES. BY DR. RUDOLF WOLLNY. (Continued from page 237.) THE following results were obtained by the method improved as described. The reagents were first tested, and then five blank experiments were made, 3 C.C. NaHO and 6 C.C. alcohol being treated without fat, precisely as the sample to be analysed, namely, they were boiled for 15 minutes under a reflux condenser, the alcohol distilled off in 15 minutes ; 100 C.C. of boiled distilled water were added, and the solution kept hot in a water bath for the same time, and ultimately distilled with 40 C.C. H,SO, and two small pieces of pumice; the distillate, measuring 110 c.c., was filtered, and 100 C.C.were titrated. The figure thus obtained, due to the volatile acid contained in the mda solution and to the carbonic acid unavoidably absorbed, was subtracted from the analytical results furnished by the various fats. In the second column of the subjoined table the corrected numbers are found, indicating exactly the vobtile f a t t y acids. ANALYSES MADE BY R. WOLLN~. C.C. deci-normal alkali NO. 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 Substance examined. 3 C.C. NaHO 9 9 9 , 1s 9 9 7, 9 , 9 9 77 Blank experiment 9 , 9 , 1, 9 , 9 ) 99 9 , 1 ) Beef fat Earthnut oil 9 , 2 9 9 , Sesam Oil Cotton Oil 9 9 ? f 7, ?, Oleomargarine Pure Butter 7, 7 Consumed Corrected. Calculated -A r--- - - *30 *30 -30 .no 4 5 -- - -3 5 -35 -30 *30 --.-2 5 -33 003 -33 *03 -33 .03 -33 .03 *33 .03 -3 3 .03 .44 .14 .39 .09 .39 .09 .39 .09 - - _- __ - - - - . _ - _- _- - - _ _ - - -_ - 1 - - - - __ 28.82 28.52 __ 28-93 28-63 - 28-71 28.41 - 28.93 28.63 _- 28.58 -_ 28.88 28-82 28-52 __ 28.82 28.52 - 82-77 28.47 --_THE ANALYST. 9 C.C. deci-normal alkali. NO. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 156 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 , Substance examined. Consumed. Corrected. Pure Butter 28.82 28.52 9 , 9 9 28.88 28 58 9 9 9 9 20.45 20.1 5 2 } 9 9 9 9 ( 9 , 9 , Y, 99 ) 1.43 1.54 ;:;;} 9 , ;:;: \ 9 9 2 8.34 40 -1 9 , 9 9 ( 9 9 9 9 ,, ) 14-74 14.44 } Margarine 1 (2 per cent. Butter) -88 9 9 9 ) ( 9 , 9 9 19 ) -88 9 9 2 (4 $ 9 9 9 3 (6 99 9 , ) 1.98 9 ) ( 9 9 9 9 9 9 ) 2.04 9 9 ( 9 , 9 , ,, ) 2.70 9 , 4 (8 99 ,, ) 2.64 9 , 3 00 9 , f, (10 ? ? ,, ) 3.19 9 9 J 9 ( 9 9 9 ) .) 3.30 9 , 6 (50 7, ,, ) 14-63 14.33 9 , 7 (85 9 , ,, ) 24.64 24-34 19 ( 7 9 1, ,, ) 24.86 24.56 } 9 , 8 (90 9 , ,, ) 36.51 25.21 ?9 9 9 (?, 9 , ,, ) 26.18 25.88 } $ 9 9 (95 9 7 ,, ) 27-61 27.31 3 C.C. NaHO -17 - -2s __- .32 - ANALYSES MADE BY A. SANGER. Blank Experiment .22 - 9 9 9 ) -- 9 , P9 -22 9 9 -32 9 9 9 , 7 9 -- Oleomargarine -28 *06 9 9 9 8 -06 9 9 -28 -06 19 9 8 -06 9 , *22 -00 Pure Butter 29-25 28.93 ,? 2, 29.15 28-93 Y ? Y ? 29.1 5 28.93 9 9 9 , 28.82 38-60 9 , 9 9 28.82 28.60 9 9 ? 9 28.99 28.77 9 9 9 9 28.99 28.77 ?9 2 9 28.82 28.60 :g } ;:;; } 9 9 9 9 ( 9 9 7 9 ,, ) 2.15 1-93 } 9 9 ?, ( 9 , 99 Y9 ) 2-64 8.42 } Margarine 1 (2 per cent. Butter) *77 9 9 $ 9 ( 9 9 9 , 9 9 ) *88 9 , 2 (4 9 , ,, ) 1.54 9 , 19 ( 9 , 9 9 9 9 ) 1-49 9 9 3 (6 9 9 1, 4 (8 9 9 ,? ) 2.64 2.42 ,, ) 2.09 1.87 Calculated ’ - - - -62 1.20 1.77 2-34 2-92 14.35 24.35 25.79 27-23 *G2 1.80 1.77 2.34- - ~ THE ANALYST._. l o - C.C. deci-normal alkali. -7 ,-.----A NO. 180 181 182 183 184 185 186 187 188 Substance examined. Consumed. Margarine 5 (10 percent. Butter) 3.08 7 9 G (50 7 7 7 , ) 14.47' 9 9 7 (85 7 7 ) 24.31 7 7 9 7 t 9 9 7 7 ,, ) 3.0s 17 ? 7 ( 7 9 7 7 ,, ) 14.41 9 7 9 7 ( 9 7 7 , 7 7 ) 24.42 7 7 8 (90 7, ,, ) 26.7'4 7 9 7 9 ( ? 7 7, ), ) 25.95 9 7 9 (95 9 ) 9 7 ) 27.50 189 Cotton Oil 190 7 ) 7 ) Substance examined. Beef-fat.Oleomargarine. Earthnut oil. Sesam oil. Cotton oil. Butter mixture, 2 per cent. ?? 4 ,? 77 6 J ? ? ? 8 7 7 77 10 ?? ,? 60 j? 1, 86 ,, ?? 90 ? 7 J 7 9.5 ,, Pure butter. SUMMARY OF ANALYSES. Results by modified method. Min. 1 *03 *03 -03 *09 *55 1.13 1.68 2-34 2.86 14.19 24.09 26.52 37.28 28.41 - Max. 9 *03 *03 *03 -14 -66 1-35? 1.93 2.42 3.00 14-44 .24*66 27-31 "8.93 - 26.31 Corrected. 2.86 3.86 } 14.25 1 14.19 J 24.09 24.20 } 25-58 35.73 } 27.28 Mean. 3 *03 *03 S O 3 .11 -69 1.24 1.81 2.40 2-90 14.30 24.30 25.84 37-30 98.65 - Resnlts by Meissl method. Min. 4 -26 *19 *63 * i d 1-07 1 *84 3.39 2.83 3.16 16.04 24.94 26.04 2'7.76 28.93 - Max. 6 -92 1.29 1.07 -74 1.68 2.13 3 -60 3.31 3.89 15-88 2;5*3p 26.55 28.21 30.55 - Calculated. 2.92 14.35 24.3 5 25.79 27.22 I -~ )ifferences of 4 and i compared with 3.Min. Max. The soda solution used by myself had been filtered through glass-wooi, but was slightly turbid from suspended carbonate; that used by Sanger was quite clear, and the latter, therefore, found somewhat less volatile acid in the alkali used than I did. I n experiment 135 the soap solution had been allowed too become cold and had con- sequently gelatinised. The fatty acids separated from it were therefore solid and fused only towards the end of the distillation. The volatile acids obtained consumed only 20.15 C.C. instead of 28.65 C.C. It is necessary therefore that the soap solution should be decomposed when having a temperature of not less than 50 to 60° C . The correct figures of column 2 agree very well with the calculated ones.The volatile fatty acids passing into the distillate correspond therefore to the total quantities contained in the soap, and hence it is possible to calculate accurately the percentage of butter contained in mixtures, when the fluctuations of volatile acids in different butters have been ascertained by further experiments. A11 estimations hitherto made areTHE ANALYST. 11 defective, for reasons already stated. The same applies to the estimations of volatile acids in the various materials entering into the composition of butter-substitutes. The method of analysis, as modified by me, satisfies all reasonable demands which may be made, and complies with the requirements of Clause 2 of the German Margarine Bill. The object of the present investigation has so far been directed towards conducting the saponi~'ication in a manner free from sources of error ; I now proceed to the second part of the research, viz., to ascertain the conditions of distillation whereby absolutely uniform results may be obtained.This object has already been attained in materials yielding small amounts of volatile acids; but in the case of butter and mixtures con- taining a large percentage of it, differences tip to -7 C.C. have been observed. It became necessary therefore to study all conditions which might influence the result of the distillation. I n the first place, it appeared of interest to ascertain the total amount of volatile acids contained in butter, respectively how much could be obtained by repeated distillation of the decomposed soap.Experiments 191-20%-5 grms. butter-fat were saponified and decomposed as usual ; after 110 C.C. had been distilled off, 110 C.C. distilled water were added, and the like amount again distilled off; this was repeated twelve times. The distillates required the following quantities of deci-normal solution :- 1. 28-16 5. *33 9. 9 8 2. 2.20 6. *33 10. -28 3. *77 7. -3 3 11. -22 4. -50 S. -3 3 12. -32 a total of 33-05 c.c., the distillation not being quite completed even then. Similar series of experiments (203-217) were made with three other samples of butter. 1. 2. 3. Distillate 1 26.74 27.99 31.29 1, 2 2.97 2.86 3.41 9 9 4 -55 955 a 6 6 7, 3 -8% -77 1.10 9 9 5 -44 -44 -44 31-58 me1 36.90 The quantities of volatile acids obtained in the first distillate are therefore fairly proportionate to the total amounts, and no advantage could be derived for analytical purposes by repeated distillations. The molecular weight of tlie volatile acids contained in the various fractions of butter 3 were next ascertained by weighing the baryta salts. That of t,he first and main fraction was found to be 96, whilst the insoluble portion of the fatty acids passing over with the first distillate was 197, and with the further distillates 251. The soluble acids therefore chiefly consist of butyric acid, the insoluble ones correspond with palmitic acid. 100 grms. of a 5 per cent. solution of pure butyric acid were distilled and each portion of 10 C.C. of the disbillate titrated with normal soda. The various fractions consumed 10.0, 9.4, S.3, 7.3, 6.2, 5.1, 3 * S , and 2.9 c.c., the remainder in the retort, measuring about 20 C.C. using 2.0c.c. Na.130. (To be concluded.) Experiment 218.

ISSN:0003-2654    

DOI:10.1039/AN8881300008

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

12 THE ANALYST. ESTIMATION OF POTASSIC BITARTRATE I N WINE-YEAST AND CRUDE CREAM OF TARTAR. BY ARTHUR BORNTRAGER. (Concluded from page 242.) A mixture of 1.875 grms. of this sample mixed with *625 grm. calcic tartrate and some acid calcic phosphate gave 99.52 per cent. potassic bitartrate. I had the same ideain my mind before Klein published his process, but I always thought it would be necessary to make an allowance for the slight solubility of the cream of tartar in the 10 per cent. solution of potassic chloride. A 10 per cent. solution of potassic chloride retained in 100 C.C. -0376 grm. of bitartrate a t a temper- ature of 11.5-13-5°C. and -0583 grm. a t 28-29°C. I n Klein's experiments there must, therefore, have been a loss of about 1.66 per cent. of cream of tartar. Further experiments have also convinced me, it makes no difference whether the liquid is filtered off after standing for only half an hour (after ten minutes vigorous stirring), or allowed to stand all night.A cream of tartar thus treated gave 99.6 instead of 99.87. I have since made experiments which confirmed my dews. SOLUBILITY OF POTASSIC BITARTRATE IN 10 PER CENT. SOLUTION OF POTASSIC CHLORIDE AT ORDINARY TEMPERATURE. 1-25 grms. bitartrate were dissolved in about 125 C.C. boiling water, and after cool- ing mixed with 10 grms. OF potassic chloride for every 100 c.c., stirred well for 10 minutes, and after standing for half an hour filtered off. The acidity was then taken with soda in 50 C.C. of the filtrate, I n the table the soda is given in C.C. N soda.TABLE Ir. Temperature of flnid- N. soda. Bit,artrate C.C. in 100 C.C. ' Before After After 10 After' adding adding minutes' standing KC1. KC1. standing half-hour. SG.5OC. 21 OC. 23.5OC. 24.5QC. -13 ,0488 . . .. . . * . *13 .. 18-5 15 17.5 17.5 .ll -0432 .. .. .. .. -12 .. I further once more determined the amount of bitartrate which separates after standing over night from a solution of 2.5 grms. of cream of tartar is 55 C.C. of water with addition of 5 grms. potassic chloride. The crystals were first washed with a 10 per cent. solution of potassic chloride saturated with cream of tartar. The further washing with 10 per cent. potassic chloride without cream of tartar is superfluous, as will be seen from Table IV. TABLE 111. Temperature of liquid- / b Midnight.At time of N. Soda. Bitartrate found- filtering. C.C. Grms. Per cent. Day. 23.50C. 2ooc. 19*5vC. 13.06 2.4553 98.21 20.5 19-5 20.5 13.05 2.4534 98.14 22.5 20 21 13-08 2,4590 98.36 The following results were obtained after allowing to stand for only half an hour.THE ANALYST. 13 The crystals in the first six experiments were finally washed with a 10 per cent. solution of puve potassic chloride. TABLE IV. Temperature of fluid-- 'Before After 7 adding adding After stirring. After filtering. N* Soda* Bitartrate found. KC1. KC1. C.C. Grms. Per cent. 27.5OC. 23-5OC. 23.5"C. 23.5OC. 13.04 2.4515 98.06 35-5 21.5 22.5 83.5 13.05 \ 17.5 .. 13.5 .. 16.5 .. 17.5 .. 13'05 } 2.4534 98-14 13.05 24 20 22 23.5 13.05 23.5 15.5 18.5 31.5 13.08 2-459 98.36 22 17.5 20.5 21.4 13.04 2.4515 98.06 20.5 22.5 16.5 18-5 18.5 20.5 20 21.5 The results of the following table were obtained by treating 2 grammes of cream of tartar with 40 C.C.of boiling water, and after cooling adding the potassic chloride. After 15 minutes stirring and half an hour's stsnding the crystals were washed with 10 per cent. solution of potassic chloride (saturated with cream of tartar), TABLE V. Temperature of fluid- .I h * After At time of N. Soda. Bitartrate found- stirring. filtering, C.C. Grms. Per cent. Before After adding adding KC1. KC1. 2 3 T . 17-5OC. 21-5"C. 22.5W. 10.44 1.9627 98.14 . . . . .. . . 10.46 1.9655 98.32 16.5 12.5 15.5 17 10.48 1.9702 98-51 1.9665 98.32 . . . . .. .. 10.46 1.9702 98.51 .. . . .. . . 10.48 I therefore propose to add 00330 grm. of potassic bitartrate to the quantity found As I had found that cream of by Klein's process before calculating the percentage.tartar acts on gypsum most probably according to the formula- CaSO,L + 2 KHC4H406= K,SO, + CaC4H40, + H2C4H406, I made experiments to ascertain the influence of gypsum in-the analysis of tartar by Klein's process. A mixture of 2 grms. of potassic bitartrate and -3 grm. of gypsum was exactly treated according to Klein's directions. For the first extraction I used 30 C.C. water; for the following I used less. I n experiment A, I boiled first for five minutes; in the others, ten minutes, so as to see whether longer boiling makes a difference. The insoluble matter was washed on the filter with boiling water until quite free from sulphates. The filtrates were boiled down t o 40 c.c., mixed with 5 grms.of KCI, and treated as usual. Experiment A took 10.27 C.C. N Soda= 1.9308 KHC,H,06 or 96.54 per cent. The presence, therefore, of about 13 per cent. of gypsum makes even Klein's process uncertain. I now must call attention to another source of error affecting Klein's process and the casserole. Warington has often found in yeasts and tartars a crystallised calcic carbonate, most likely fraudulently added. This is only soluble with ,the greatest diffi- Experiment B =I 0.14 N S or 1,9063 grms.= 95.31 per cent.14 THE ANALYST. culty in cream of tartar, whilst amorphous calcic carbonate is readily attacked. We must, however, not forget that in the process of purifying cream of tartar on the large scale, the time of boiling lasts a good deal longer than in the casserole or Klein's method.SO to find out the influence of crystallised calcic carbonate (which in samples of tartar may be noticed with a magnifying glass), I made the following four experiments :- 4.38 grms. of bitartrate were mixed with -5 grm. of finely powdered pure Iceland spar and 50 C.C. of water. The four mixtures were respectively boiled for 5, 10,30, and 60 minutes ; then a t once neutralised. After ti minutes' boiling used 17*G2 C.C. N S. Carbonic acid was already evolved in the cold. 7 9 10 9 , 7, 17.12 ,, 9 , 30 9 7 9 7 16.86 7, 9 , GO 1 ) , 16.00 ,, I f the calcic carbonate had fully acted, only 13.30 C.C. N S would have been required. I n practice, the neutralising power of the calcic carbonate will chiefly depend on its state of division. The presence of calcic carbonate in tartars diminishes the yield of crystals, as insoluble calcic tartrate is formed, and the mother liquid contains uncrystallisable neutral potaesic tartrate.This may be partially remedied by adding to the mother liquor a definite quantity of sulphuric acid, which will again form the bitartrate. I n the analysis of such a mixture it is the best thing to add, besides the potassic chloride, about 5 C.C. of acetic acid, which does not influence the accuracy of the process, as will be seen from Table VI. 2.5 grms. of bitartrate were dissolved in somewhat less than 55 C.C. of hot water; the liquid, after cooling, was diluted with glacial acet'ic acid exactly up to 55 c.c., and then mixed with 5 grms. of potassic chloride. After standing over night the crystals were washed 15 times with a 10 per cent. solution of potassic chloride (saturated with cream of tartar) and then titrated. TABLE TI. Midnight. At time of filtering. C.C. C.C. 2O@C. 23*5@C. 050 13*OG 2.4553 98.21 19 20 1 *30 13.07 2.4572 98.29 .. 21 4.75 13.05 2.4534 98-14 19.5 21 9.50 13.07 3.4572 98.29 If Verniere's proposals (treating the calcic tartrate with sulphuric acid, and making the tartaric acid thus liberated into cream of tartar by means of a potash salt) should find universal favour with the manufacturers of cream of tartar, the best plan will be t o try and estimate as accurately as possible the total amount of real tartaric acid, and follow as closely as possible the actual process of manufacturing. Temperature of fluicl- Acetic acid. N Soda. Bilartrate. Grms. Per cent,

ISSN:0003-2654    

DOI:10.1039/AN8881300012

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年代:1888

数据来源: RSC

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14 THE ANALYST. THE CHEMISTRY OF TYROTOXICON, AND ITS ACTION UPON LOWER, ANIMALS." BY VICTOR C. VAUGIIAN, M.D., PH.D. SINCE making my last report on the investigations concerning the nature of tyrotoxicon, I have continued my work, aided greatly by Messrs. F. G. Novy and E. V. Riker. We * From thc Arncricm Piha~macisf.THE ANALYST. 15 Boon ascertained that if some butyric acid ferment bo prepared as is ordinarily done in the preparation of butyric acid, and some of this be added to normal milk, and the whole be kept in closely stoppered bottles for eight or ten days, the poison will be developed in the milk in considerable quantity. The milk should be filtered, the filtrate neutralised with sodium carbonate, and then extracted with ether. Having a strong solution of the poison in absolute alcohol, which had been obtained from milk inoculated as stated above, we added to it some platinum chloride, and began to evaporate on the water-bath.As soon as the alcohol evaporated the residue exploded with great violence. The experiment was repeated a number of times with like results. From some of this alcoholic solution the platinum was removed with hydrogen sulphide gas; but the filtrate was then found to have lost its explosive property. This reminded us that diazobenzol compounds form with platinum chloride a highly explosive salt, and that diazobenzol is also decomposed by hydrogen sulphide. Some diazobenzol was prepared according to the method of Griess (Annalen cler Chenzie und cler Pharmacie, vol. 137), and comparisons made between this and tyro- toxicon.With equal parts of sulphuric acid and carbolic acid tho prepared diazobenzol nitrate gave a green coloration, while with the same reagents tyrotoxicon gave a colour which varied from a yellow to an orange-red. But the diazobenzol nitrate dissolved in the whey of normal milk, and extracted with ether, or in the presence of other proteids, gave the same shades of colour as the tyrotosicon did, and the potassium compound of the tyrotoxicon, prepared by the method to be given later, gives the green coloration. This colour test may be used as a preliminary test in examining milk for tyrotoxicon. It is best carried out as follows :-Place on a clean porcelain surface two or three drops each of pure sulphuric acid and pure carbolic acid.This mixture should remain colour- less or nearly so. Then add n few drops of the aqueous solution of the residue left after the spontaneous evaporation of the ether. If tyrotoxicon be present an orange-red to a purple colour will be produced. This test is to be regarded as only a preliminary one, for it may be due to the presence of a nitrate or nitrite. The tyrotoxicon must be purified according to a method to be given farther on before the absence of a nitrate or nitrite can be positively demonstrated. I n the filtrate from milk which is rich in tyrotoxicon, after neutralization with sodium carbonate, filtration, and acidifying with hydrochloric acid, gold chloride produces a precipitate, which is insoluble in water, but soluble in hot alcohol, from which it separates on cooling in golden plates.Diazobenzol gives with gold chloride a precipitate having all these properties. I n both cases the gold compound is decomposed by frequent treatment with hot alcohol, and this fact prevented any satisfactory ultimate analysis of this compound. It should be remarked here that from some samples of milk this gold salt is obtained much more easily than from others, and the difference is dependent not so much upon the amount of tyrotoxicon present, as upon tthe condition of the other organic matter present. It is best obtained from samples which have stood in well stoppered bottles for a month or longer. Thinking it not likely that the diazobenzol existed in the cheese and milk as a nitrate, we prepared some diazobenzol butyrate, and found the crystals of these to agree exactly with those of tyrotoxicon, and that they decomposed with like rapidity when exposed to moist air..16 THE ANALYST. From tyrotoxicon obtained from milk, diazobenzol-potassium hydrate was obtained according to the method of Griess, and the per cent. of potassium in this compound was determined, The filtrate from the milk, which had been inoculated with the ferment, and kept in a stoppered bottle in a warm room for ten days, was neutralized with sodium carbonate, agitated with an equal volume of absolute ether, allowed to stand in a stoppered flask for twenty-four hours, the ether removed and allowed to evaporate from an open dish. The aqueous residue was acidified with nitric acid, then treated with an equal volume of a, saturated solution of potassium hydrate, and the whole concentrated on the water-bath.On being heated the mixture became yellowish-brown, and emitted a peculiar aromatic odour. Both the colour and odour corresponded exactly with the colour and odour produced by carrying some of the artificial diazobenzol through a com- parative test. On cooling the mass crystallised, the diazobenzol-potassium hydrate appearing in the test with the tyrotoxicon, and in the comparative test also, in beautiful six-sided plates, along with the prisms of potassium nitrate. The crystalline mass was treated with absolute alcohol, filtered, the filtrate evaporated on the water-bath, the residue dissolved in absolute alcohol, from which the diazobenzol-potassium hydrate was precipitated with ether.The precipitate was collected, washed with ether, dried, and the per cent. of potassium estimated as potassium sulphate. 0.2045 gram. of the diazobenzol- potassium hydrate yielded 0.109 gram. of potassium sulphate. Per cent. of potassium calculated, 24.42 ; found, 23.92. Chemists will now appreciate the great difficulty that has been experienced in isolating the active agent of poisonous cheese. The readiness with which diazobenzol decomposes is well known. When warmed with water it breaks up into carbolic acid and nitrogen. Hydrogen sulphide decomposes it ; therefore all attempts to obtain the poison by precipitating it with some base, such as mercury or lead, and then removing the base with hydrogen sulphide, have failed. Moreover, diazobenzol is only a transition product of putrefaction. I have frequently found that leaving some milk rich in the poison in an open beaker for twenty-four hours would be sufficient t o destroy the whole of the poison.The following experiments will show that the effects of tyrotoxicon and diazobenzol upon the lower animals are identical :- Experiment l.-Trom one half gallon of some milk which had stood in a tightly stoppered bottle for three months, there was obtained quite a concentrated aqueous solu- tion of the poison, after the spontaneous evaporation of the ether. Ten drops of this placed in the mouth of a small dog three weeks old caused within a few minutes frothing at the mouth, retching, the vomiting of frothy fluid, rapid breathing, muscular spasm over the abdomen, and, after some time, watery stools.The next day the dog seemed to have partially recovered, but was unable to retain any food. This condition continuing for two days, the animal was killed with chloroform. No examination of the stomach was made. Experiment 2.-Tyrotoxicon obtained from poisonous ice-cream was given to a cat. Within ten minutes the cat began to retch, and soon it vomited. The retching and vomiting continued for two hours, during which time the animal was under observation, and the next morning it was observed that the cat had passed several watery stools.THE ANALYST. 17 -~ After this, although the cat could walk about the room, it was unable to retain any food. Several times it was seen to lap a littlemilk, but on doing so it would immediately begin to retch and vomit.This condition continuing, after three days the animal was placed under ether, and its abdominal organs examined. We certainly expected to find marked inflammation of the stomach ; but we really did find the stomach and small intestines filled with a frothy serous fluid, such as had formed thevomited matter,and the mucous membrane very white and soft. There was not the slightest redness anywhere along the alimentary canal. Experiment 3.-Some tyrotoxicon obtained from milk which had been inoculated with poisonous cream, and allowed to stand for forty-eight hours, was administered to a large old cat. The amount of the poison administered in this case was small. Experiment 4.-Some tyrotoxicon from milk was given to a young, but full-grown cat.Within fifteen minutes there was marked and evidently painful retching, and within half an hour vomiting accompanied by [rapid breathing. Later there were several stools, the first two of which contained fecal matter ; but subsequent ones were rice-water like, and wholly free from fecal odour. After two days some more of the poison was given, and the vomiting and diarrhcca again induced. The animal was then anaesthetized, and examination of the stomach and intestine showed the mucous membrane blanched, as was found in experiment 2. We have the records of a number of other experiments with tyrotoxicon on the lower animals; but as the symptoms induced in all were substantially the same, it is un- necessary to note them here. We will now give the effects observed in the lower animals after the use of the prepared diazobenzol. Experiment &-Gave to a large old cat 100 milligrams.of diazobenzol butyrate, Immediately the animal began to purge. Then she lay upon the floor breathing rapidly and retching severely for two hours, when she died. The retching was most violent, but vomiting seemed impossible. Post-mortem examination showed the lungs greatly congested, but the mucous membrane of the stomach and intestine was not reddened. The stomach contained some food. I suppose that the congestion of the lungs was due to the violent retching. Experiment 6.-To a young, but full-grown Maltese cat I gave 100 milligrams. of diazobenzol butyrate. With most violent retching, but without either vomiting or stool, the animal died within thirty minutes after the administration of the poison.The lungs were found acutely congested, and the stomach free from any redness. The circular fibres of the small intestine were tightly contracted. Experiment 7.--Gave to a full-grown cat 25 milligrams. of diazobenzol butyrate. Within ten minutes vomiting and purging were induced. The first stools contained fecal matter ; but the subsequent ones were like rice-water, and wholly free from fecal odour. After two days the cat was able to take food; then 10 milligrams. more of the poison were given, with the reproduction of the vomiting and purging. The animal then rapidly emaciated, and after a few days it was anresthetised, and the mucous mem- brane of the stomach and intestine found blanched. Experiment &-lo milligrams.of the poison produced prof use diarrhcea, and con- tinued vomiting in a cat. It soon produced retching, but no vomiting or diarrhea. The lungs were not congested.18 T.HE ANALYST. Experiment 9.-75 milligrams. produced vomiting and diarrhcea with congestion of the lungs in a dog. It seems unnecessary to detail any more of these experiments, as the identity of tyrotoxicon with diazobenzol is now established, not only by chemical analysis, but this proof is strengthened, if chemical analysis can be strengthened, by the action of the poison on the lower animals, and by the post-moytene appearance. I think it highly probable that diazobenzol or some closely-allied substance will be found in all those foods which from putrefactive changes produce nausea, vomiting and diarrhma.I n some oysters which produced these symptoms I have recently found tyrotoxicon. Milk or other fluid to be tested for this poison should be kept in well stoppered bottles; for if the fluid be exposed to the air the tyrotoxicon may decompose in a few hours. The filtrate from the milk, or the filtered aqueous extract of cheese should be neutralised with sodium carbonate, then shaken with half its volume of pure ether. Time should be given for the complete separation of the ether. Purified tyrotoxicon is insoluble in ether, and it probably owes its solubility in ether at this stage to the presence of impurities. After complete separation the ether should be removed by a pipette, and allowed to evaporate spontaneously from an open dish. The residue from the ether may be dissolved in distilled water, and again extracted with ether. To a drop of an aqueous solution of the ether residue apply the preliminary test with sulphnric and carbolic acid. To the remainder of the aqueous solution of the ether residue add an equal volume of a saturated solution of caustic potash, and evapo- rate the mixture on the water-bath. The double hydrate of pohassium and diazobenzol will be formed if tyrotosicon be present, and this may be recognised by its properties and reactions which have already been described.

ISSN:0003-2654    

DOI:10.1039/AN8881300014

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年代:1888

数据来源: RSC

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18 T.HE ANALYST. NONTHLY RECORD OF ANALYTICAL RESEARCHES INTO FOOD. ESTIMATION OF FAT IN MILK. - MORSE, PIGGOT, AND BunToN.-This method con- sists in the dehydration of the milk by means of anhydrous sulphate of copper; the extraction of the fat by means of the.low-boiling products of petroleum ; the saponification of the butter by means of an excess of a standard solution of potassium hydrate in alcohol; and the determination of the excess of the alkali by means of a solution of hydrochloric acid. The following apparatus and reagents are required :- (1) A porcelain mortar and pestle. (2) An extraction tube, 14 or 15 mm. in diameter, 220 mm. in length, with funnel- (3) A 200 C.C. Erlenmeyer flask, strong enough t o be used with a filter pump. (4) A suitable stand for holding the flask and extraction tube.(5) Ten-cubic centimetre pipettes. ( 6 ) Weighing-glasses with ground-glass stoppers. (7) A low-boiling gasoline, distilling between 30'' and 60". (8) Dehydrated sulphate of copper. (9) Semi-normal solution of potash in 95 per cent. alcohol. ManipuZation.-Place about 30 grams. of the anhydrous copper sulphate, roughly measured in a copper spoon of the size to hold about that amount, in a porcelain mortar ; shaped top. A straight chloride of calcium tube may be used for this. (10) A semi-normal solution of hydrochloric acid.THE ANALYST. 19 make a cavity in the centre of the mass with the pestle. Allow 10 C.C. of the milk to run on to the copper sulphate, being careful that none of it touches the sides of the mortar. When the milk is nearly dry, grind the mass up with a little clean sand, transfer to the extraction tube, gently pressing it down in the tube by means of a glass rod. The lower portion of the extraction tube to be packed with clean cotton wool. The fat is extracted in the following way : 15 C.C.of benzene is poured over the material in the extraction tube and drawn down with the aid of the filter pump, until the whole of the mass to be extracted has become wet with the liquid, when the connection with the pump is closed; after about five minutes another portion of 15 C.C. of benzene is poured into the tube and the whole of the liquid slowly drawn through with aid of the pump into the flask. Usually one extraction of this kind is sufficient to withdraw the whole of the butter, but for the sake of greater accuracy the process may be repeated two or three times. Pitmtioln.-The benzene may be evaporated and the residual butter fat saponified with about 25 C.C. of the appoximately semi-normal potash. The residual alkali is determined by means of the semi-normal hydrochloric acid, using phenol-phthalein as indicator. The difference between the amount required in this process and the amount necessary to neutralise the quantity of alkali taken gives the amount of alkali required for the saponi- fication, The number of milligrams. of potash required for one gram. of the fat is taken a t 230. The fat may also be accurately titrated without evaporating the benzsne. W. H. D.

ISSN:0003-2654    

DOI:10.1039/AN8881300018

出版商:RSC    

年代:1888

数据来源: RSC

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THE ANALYST. 19 MONTHLY RECORD OF GENERAL RESEARCHES I N ANALYTICAL CHEMISTRY. ANALYSIS OF POTASSIUM-ANTIMONIUM FLUORIDE. By G. STEIN. Chem. Zeit., 84. -. This double salt is now extensively used in dye-works, instead of tartar emetic, on account of its low price. To qualitatively test for its purity, the author adds potaesic ferrocyanide, which should give no blue colour, and baric chloride, with a little hydro- chloric acid, should give no turbidity. It is, of course, better to make a quantitative analysis, which is easily performed, as follows :-*5 grm. of the compound is dissolved in hot water, and after adding a few drops of phenol-phthalein, rendered just alkaline with ammonia. The precipitated antimonic oxide is collected on a weighed filter, washed, and dried a t 110" C,, and weighed.The yield should be 66 per cent. L. DE K. REACTIONS OF OAK-BARK TANNIN. C. B~TTINGER. Liebig's Ann., 240.-The assay of tanning materials is still so unsatisfactory that everything which throws light on the subject must be considered welcome, The author has found the true oak-bark tannin to behave to bromine in a different way from other tannins, in so far as it yields a brownish yellow deposit, Cl,oH,4Br20,,, which shows the following reactions : It is with difficulty soluble in water, but readily so in a mixture of alcohol and acetic ether. This solution gives, with cupric sulphate, a precipitate ; with ferro and ferricyanides, a green turbidity ; and with ferric chloride, the usual blue black. It explodes when fused with solid potassic hydrate. When again heated with anhydrous bromine it passes with effervescence into C,,H,,Br,O,,, a reddish compound, which is easily soluble Alkalies soon dissolve it.in alcohol, carbon disulphide, acetic acid, alkalies, and ammonia. L. DE K. AMMONIC DITHIOCARBAMATE AS A REAGENT. J. KLEIN. Repert Anal. Chemie, 42, 43.-The action of carbon disulphide on an alcoholic solution of ammonia produces not only the ammonic dithiocarbamate, but also the sulpho-carbonate. To obtain the first in a pure state Mulder's process is the best,, Ammonia gas is evolved from a mixture of20 THE ANALYST. 150 parts of sal ammoniac and 300 parts of quicklime, and passed into 600 parts of strong alcohol. When the temperature is kept a t 30° C only the dithiocarbamate will crystallise out, which must be washed with a little strong spirit, and dried between blotting paper. I f after exposure some particles turn reddish, these must be rejected.To see if the salt is really free from sulpho- carbonate add a little to an ammoniacal solution of nickel sulphate when no red colour should develop. The salt keeps far better as a 5 per cent. watery solution than in the solid state. As will be seen, it may be conveniently used instead of sulphuretted hydrogen, for the separation of many metals. Action on copper :-A solution of a copper salt, which must contain free HCl is completely precipitated on boiling, cupric dithio- carbamate being precipitated as a yellow powder which may be washed and collected without loss. The author prefers to ignite it in a current of hydrogen, and so form cuprous sulphide, which is then weighed.Iron, manganese, nickel, cobalt, alkaline earths and alkalies ?re not affected. Zinc comes down slightly with the copper, but may be removed by a second precipitation. This double precipitation is, in fact, always advisable when the copper is present in relative small quantities. Inapply- ing the process to brass, dissolve the alloy in nitric acid, evaporate with hydrochloric acid to dryness, dissolve residue in water containing about 5 per cent. HCl, boil and add the reagent. The precipitated copper is, after washing, redissolved in nitric acid and once more similarlyvtreated. Action on zinc, etc. :-Zinc is completely precipitated on boiling if the liquid contains no free hydrochloric acid ; free acetic acid, if not present in too large amount, does not prevent the precipitation.The author therefore recommends the addition of a little sodic acetate. The precipitate may be collected and washed without loss, and is, like the copper, best made into zinc sulphide before weighing. Ferric salts are reduced to ferrous salts, which are thrown down from a neutral solution. Nickel, cobalt, and manganese are but incompletely precipitated, even from an ammoniacal solution. Aluminium and chromium :-Aluminic sulphate is thrown down on boiling, probably as hydrate, with evolution of sulphuretted hydrogen. Chrome alum gives a precipitate, partly consisting of hydrate, partly of a blue body of a complex nature. The filtrate is also coloured blue. I n presence of free acid chromates am reduced to chromic salts.Mercury, lead, silver, bismuth, cadmium, all yield characteristic precipitates. Cadmium may be separated from copper by first adding excess of ammonia and potassic cyanide, then an excess of the dithiocarbamate. Copper and mercury may also be similarly separated, using soda ley instead of ammonia. The copper may be recovered from the filtrate by adding hydrochloric acid. Tin and antimony also yield characteristic precipitates, but the author attaches great importance to the power of the reagent to precipitate arsenic, as there is no doubt it can be got absolutely Finally 95 parts of carbon disulphide are added. On heating the cadmium is precipitated. free from arsenical impurities. L. DE I(. BOOKS, &c., RECEIVED, AMEI~ICAN Analyst; American Chemical Review ; American Druggist ; American Grocer ; American Journal of Pharmacy ; Brewer’s Guardian ; Canadian Pharmaceutical Journal ; Chemist and Druggist ; Country Brewer’s Gazette; Druggist’s Circular ; Hospital Gazette ; The Illustrated Sidney News ; Indea pendent Journal; Invention; Journal of t h e American Chemical Society; Journal of Microscopy and Natural Science ; Justus Liebig’s Annalin der Chemie ; Journal of the Society of Chemical Industry ; Le Nouvement Hygienique ; Medical Press ; Nedical Record ; The Miller ; Monthly Magazine of Pharmacy and Chemistry ; National Druggist ; Pharmaceutical Journal ; Pharmaceutical Record ; The Polyclinic ; Popular Science News ; Repertorium der Analytischen Chemie ; San Francisco New8 Letter ; Scientific American ; Society of Arts Journal. NOTICE TO CORRESPONDEBTS. Communications on Literary or Exchange Matters to be sent t o 325, Bennihgtoh Road, London, SIE,

ISSN:0003-2654    

DOI:10.1039/AN8881300019

出版商:RSC    

年代:1888

数据来源: RSC