摘要:

THE ANALYST 3 ‘( The Detection and Estimation of Formaldehyde in Milk,” by Herbert S. Shrewsbury, F.I.C. and Arthur W. Knapp B.So. F.1.C “The Determination of Aldehydes i n Oil of Lemon,” by A. H. Bennett ; and ‘< Some Analyses of Cream Cheese,” by Cecil H. Cribb B.Sc. F.I.C. * * % + I +

ISSN:0003-2654    

DOI:10.1039/AN9093400001

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

THE ANALYST 3 THE GRAVIMETRIC ESTIMATION OF ANTIMONY AND TIN. BY EDWARD CAHEN, A.R.C.S., A.I.C., AND GILBERT T. MORGAN, D.Sc., F.I.C. (Read at the Meeting, December 2, 1908.) AT the suggestion of the Analytical Chemistry Investigation Committee of the Society of Public Analysts, a detailed examination has been made of the method recommended by Vortmann and Metzl (Zeit. Anal. Chem., 1905,44, 525 ; ANALYST, 1905, 30, 281) for the quantitative separation of antimony from tin. The results obtained in this investigation rendered it desirable to extend the work in order to compare this process with other methods which have been suggested for the gravimetric separation of these two metals. I. VORTMANN AND METZL'S ESTIMATION OF ANTIMONY. Preliminary experiments were carried out with the view of ascertaining whether antimony, in the absence of tin, could be precipitated completely by the two methods proposed by these authors.1. Precipitatio?% in HydrochEoric Acid.-Antimony oxide was dissolved in the least possible amount of hydrochloric acid, a few drops of phenolphthalein added, the solution neutralised with caustic soda, and made up to 50 C.C. A known excess of hydrochloric acid (24 C.C. of specific gravity 1-16} was then added, and the solution maintained at the boiling-point in a water-bath while a rapid stream of sulphuretted hydrogen was passed in for about thirty-five minutes. The antimonious sulphide which separated at first in the flocculent orange hydrated form changed into the black crystalline anhydrous modification, this transformation being promoted by the vigorous agitation of the mixture.The liquid was then diluted to twice its bulk, when a slight yellow cloudiness appeared, which was speedily dispelled by the further passage of the gas. The crystalline precipitate was now dealt with in the manner indicated in section 3, being collected in the modified Soxhlet tube, and weighed after drying at 280' C. The quantitative results exhibited in Table A show that the precipitation was complete. The precipitate was generally washed with hot very dilute acetic acid saturated with sulphuretted hydrogen. 2. Precipitation in Presence of Phosphoric Acid.-The foregoing procedure waB adopted up to the point when 50 C.C. of neutral solution were obtained. At this stage 50 C.C. of phosphoric acid (specific gravity 1.3) and 20 C.C.of hydrochloric acid (specific gravity 1-16) were introduced. The precipitation and manipulation of the antimonious sulphide were then effected as above. The results shown in Table B are in fair agreement with those obtained with hydrochloric acid alone.4 THE ANALYST. TABLE A.-PRECIPITATIOS I N PRESEXCE I TABLE B.-PRECIPITATION IX PRESENCE OF HCl. OF H3PO.p Sb,O,. Taken. 0.5063 0.6054 0.6980 0.5834 0.7262 6 u a Sb8,. Sb. Found. Per Cent. Theory = 83.3 0.5886 82.88 0.7025 82.81 0.8104 82.87 0.6777 82.96 0.8446 83.03 Sb,O,. Taken. 0.4818 0.5208 0.4970 0.8860 0-6574 0.4944 0-5804 0.5678 0.6680 0.7060 Sb,S,. Sb. Found. Per Cent. Theory = 83.3 0.5600 82.99 0.6052 82-94 0.576'7 82.81 1.0300 82-99 0,7658 83-16 0.5750 83.01 0,6756 83-10 0.6598 82.94 0,7748 82.77 0.8182 82.73 Mean .,.82.91 I Mean ... ... 82.94 3. Estiinatioit of Aiztinzony in the Presence of Tin.-Solutions of antimony and tin prepared by dissolving pure antimonious oxide and metallic tin in hydrochloric acid were treated with hydrogen sulphide in the presence of phosphoric acid as in- dicated in section 2, the current of gas being diminished con- siderably as soon as the precipitation of antimonious sulphide was completed. I t was found that discordant results were obtained by washing the black crystalline antimonious sulphide with carbon bisulphide and alcohol, and drying at 110" C. Heating of the Gooch crucible over an Argand burner, while carbon dioxide was introduced through the perforated crucible lid, was also unsatis- factory ; the air was not completely excluded, and oxidation of h sulphide occurred even at 150" to 180" C.The crucible was next heated in a small copper air-oven, which could be kept filled with carbon dioxide. Eventually oxidation was entirely prevented, and a constant temperature (280° to 300" C.) main- tained by the use of the modified Soxhlet tube shown in the accompanying figure. The glass stopper b, which carries a vertical tube c, fitted with a thermometer e, and a side tube d for the admission of the carbon dioxide, fits loosely into the broad Soxhlet tube a, and closes it round the rim by its own weight and that of the thermometer. The precipitate is collected on an asbestos mat restiag on a porcelain disc, . The heat is supplied by a small 9 ring-burner g, 1 inch in internal diameter (shown in plan and section), made to fit the tube.The carbon dioxide admitted into the Soxhlet tube is washed in aqueous potassium bicar- bonate and dried over calcium chloride.::: * Lewis A. Yontx (Jown. Amel.. Chenz. Soc., 1908, 30, 975) calls attention to the fact that it is not entirely pure antimonious sulphide which is weighed, and points out that a siiiall amount of an uTHE ANALYST. 5 The results indicated in the following table were obtained in the presence of 0.3 to 1.0 gram of tin. TABLE C.-ANTIMONY PRECIPITATED IN THE PRESENCE OF TIN. Sb,O,. Taken. 0.3180 0.3080 0.9500 0.6506 0.6242 0.2832 05645 0.6248 0.8242 0.4176 Sb S.. ObtAdd. 0.3690 0-3574 1 -1034 0.7552 0.7256 0.3286 0.6568 0.7232 0.9580 0.4846 Sb.Per Cent. 82.83 82.83 82-88 82.85 82.99 82-83 83-05 82.60 82.99 82-83 Mean ... ... 82.91 Taken. Sb,O,. 1.2008 0.6280 0.7536 0.8610 0.6204 0.5326 0.5736 0.6472 0.5788 0,4386 Obtained. Sb,S,. 1.3978 0.7304 0.8746 0.9988 0-7214 0-6186 0.6678 0.7500 0.6736 0.5082 Sb. Per Cent. 83.10 83-01 82.85 82.79 82-99 83.10 83-08 82.73 83.08 82.71 Calculated . . . 83.3 The filtrate from the antimonious sulphide was boiled, treated with hydrogen sulphide, and then nearly neutralised with ammonia, The precipitated tin sulphide was allowed to Regregate by heating the mixture on a hot plate, so that when collected it could be readily washed with dilute ammonium nitrate solution. The dried sulphide, when oxidised either by roasting and subsequent treatment with nitric acid, or by the direct action of this oxidising agent, gave high results, which showed that phosphoric acid was precipitated along vith the stannic sulphide.In fact, it was frequently found that the impure stannic oxide had completely fused at the temperature of the blowpipe. The conclusion arrived at regarding Vortmann and Metzl's method is that under certain narrowly defined conditions it is quite possible to obtain a quantitative separation of antimony from tin, but in order that the process may be effective several precautions are indispensable. One of these, the absence of nitric acid or other oxidising agent, is a condition which is not conveniently brought about when the antimony and tin are to be separated from the other metals of the sulphide group. Moreover, as stated in the precading paragraph, the method does not admit of the estimation of tin by any simple process.11. CZERWEK'S METHOD FOR ESTIMATING TIN IN THE PRESENCE OF ANTIMONY. With the object of arriving at an estimation of the tin in the alloys of this metal with antimony, an examination was made of the following method due to Czerwek (Zeit. Anal. Chern., 1906, 45, 505). The clear solution, obtained by dissolving the alloy at 40 to 45" C. in 15 C.C. of nitric acid (specific gravity 1*42), 15 C.C. of water, and 6 grams of tartaric acid, was heated to boiling, and the tin precipitated by a slight excess of phosphoric acid (specific gravity 1*3), 5 to 30 drops being oxychloride is co-precipitated with the sulphide. obtained, in spite of the volatility of the oxychloridc.Yet his data show that satisfactory results can hn6 THE ANALYST. added according to the amount of the metal present. The mixture was stirred continuously, and after diluting to 300 c.c., was left on the water-bath for fifteen minutes. The gelatinous precipitate was collected, washed with hot aqueous ammonium nitrate, dissolved in warm ammonium sulphide, and stannic sulphide was precipitated from the solution by dilute suiphuric acid after diluting the liquid to 1 litre. Other metals, such as copper and lead, which are precipitated with the tin by phosphoric acid, furnish sulphides insoluble in ammonium sulphide, and are thus separated. The filtrate from the stannic phosphate was neutralised with ammonia, mixed with excess of ammonium sulphide, warmed, and then cooled and acidified with acetic acid.The tin and antimony were finally weighed as oxides. I n putting this method into practice it was found that a mixture of tin and antimony, unlike an alloy of these metals, did not dissolve in the mixed acids. Moreover, the tin phosphate obstinately retained traces of antimony even after repeated washings with animonium nitrate or dilute tartaric acid, and finally appre- ciable traces of tin make their appearaim in the filtrates. This method of precipi- fating tin gives good results, but is quite untrustworthy for the estimation of antimony. Five estimations of tin in ammonium stannichloride gave coucordant results with a mean of 32.42, whereas the calculated percentage of tin in (NH,),SnCl, is 32.33. 111. HENZ’S GRAVIMETRIC METHOD FOR TIN AND ANTIMONY.This method was tested with mixtures of pure tin and antimony, and the separation was carried out exactly as described in the author’s original paper (Zeit. Alzorg. Chem., 1903, 37, 1), and in Treadwell’s (‘ Analytical Chemistry,” vol. ii,, p. 189. The following points of detail are, however, worthy of note : 1. The substitution of concentrated sulphuric acid for aqua regia as the solvent 2. The amount of potassium sulphide must be reduced to a minimum. 3. An excess of hydrogen peroxide is essential to the success of the operation. 4. Instead of the oven employed by Henz, the washed antimony sulphide may be 5. The tin may be deposited electrolytically in a reasonable time by the employ- of the mixed metals is detrimental to the analytical process.dried at 280 to 300” C. in the modified Soxhlet tube figured on p. 4. ment of rotating electrodes. ELECTROLYTIC ESTIMATION OF TIN WITH A ROTATINQ ANODE. A platinum gauze cylinder (4 cm. diameter and 4 cm. length) coated with electrolytic copper was employed as cathode, the rotating anode being a, platinum spiral placed along the axis of the cylinder. The current used was 2.5 to 3 amphres with 4 volts, and the anode made 700 to 900 revolutions per minute. A series of experiments was carried out with tin alone, to obtain satisfactory conditions for the complete deposition of this metal. Hydrochloric acid solutions of pure tin were treated with the same amounts of caustic potash, tartaric acid, and oxalic acid as in the Henz method, and electrolysed for one hour.Table D shows ten results obtained in this way.THE ANALYSTo TABLE D. 7 Sn Taken. Sn Found. Error. Sn Taken. Sn Found. Error. - 0°0002 + 0~0002 - 0.0012 - 0.0016 k 0~0000 0.1256 0,1712 0-1394 0.1427 0.1773 0.1250 0-1700 0.1402 0,1432 0.1772 - 0.0006 - Oa0012 + 0~0008 + 0.0005 - 0~0001 0.1270 0-1898 0.1782 0.1414 0.1414 0,1268 0.1900 0.1770 0.1398 0.1414 The filtrates from the antimony were then treated with 8 C.C. of redistilled con- centrated sulphuric acid, evaporated to about 150 c.c., and electrolysed in a tall 200-C.C. beaker covered by a split clock glass. The spray on the under surface of this cover was washed into the beaker about fifteen minutes before the end of the operation. The current, which was continued for one hour, raised the temperature of the solution sufficiently to prevent the crystallisation of the salts present. Table E shows some results obtained in the analysis of several mixtures of anti- mony and tin, the latter being estimated electrolytically with the rotating anode.TABLE E. Error. Antimony Sulphide. Antimony Taken. Antimony Found. Tin Taken. Tin Error. 0.1226 0.1794 0.1834 0.1174 0.1246 0.1138 0.1264 0.0944 0.2262 0.2082 0.0968 0.1380 0.1150 0-1134 0.1131 0.1724 0.2552 0,2536 0.1678 0.1782 0.1584 0.1776 0.1348 0.3136 0.2922 0-1398 0.1956 0.1624 0.1594 0.1600 0.1202 0.1822 0*1810 0.1198 0,1272 0.1131 0.1268 0.0962 0.2237 0-2085 0.0997 0,1392 0.1163 0.1140 0-1142 - 0.0024 + 0.0028 + 0.0024 + 0.0026 - 0-0007 + 0*0004 + 0*0018 - 0.0025 + 0.0003 + 0.0029 + 0.0012 + 0.0013 + 0*0006 + 0*0011 - 0.0024 0.1298 0.1464 0.1600 0.1212 0.1286 0.1374 0.1810 0.1460 0.1486 0.1488 0-1654 0,1502 0.1225 0*1180 0.1174 0.1274 0.1422 0,1590 0.1168 0.1228 0.1354 0.1796 0-1436 0.1462 0.1496 0.1632 0.1446 0.1206 0.1166 0,1126 - 0.0024 - 0.0042 - 0~0010 - 0.0044 - 0*0058 - 0.0020 - 0.0014 - 0.0024 - 0.0024 + 0*0008 - 0.0012 - 0.0056 - 0.0019 - 0.0014 - 0.0048 Henz’s method was tried on certain alloys of known constitution.I t was at once found to give low results for the tin in those alloys, which contained much lead. Some experiments were accordingly carried out to Bee whether the estimation of the lead would reveal where the loss of tin was taking place. Estimations of lead were therefore made in two alloys : (1) After separating the antimony and tin as oxides ; (2) after separating the antimony and tin as soluble sulphides by means of potassium sulphide, as in Henz’s method.In the first case, the alloy was dissolved in a very8 THE ANALYST. little nitric acid, evaporated nearly to dryness, boiling water added, and, after settling, the antimony and tin oxides were filtered off, the lead in the filtrate was precipitated by 1 C.C. of sulphuric acid, evaporated till strongly fuming, cooled, a little water and alcohol added, and allowed to stand overnight. The precipitate was filtered off through the modified Soxhlet tube, washed with 100 C.C. of alcohol and water (1 : l), heated to 260 to 300" C., and weighed. Weight of Alloy. 0.5014 0.5006 0-5012 0.5010 0.5012 0.5004 0.5006 0.5014 0.5014 TABLE F.-ALLoY.Weight of PbSO,. 0.4038 0.4054 0.4044 04054 0.4210 0.4200 0-4154 0.4142 0.4144 85. S b. Per Cent. Weight ofMixed Oxides. 0, 0.5967 5076 10.6033 16.72 16.55 16-50 I 0.2'620 0-2580 0.2598 Pb. Per Cent. Sb. Per Cent. 11-53 11.76 55.01 55-31 55.11 55-27 Weight ofMixec Oxides. 0.2590 0.2576 57.37 57-32 56.66 56.43 56-45, Lead spoilt 79.07 79.60 Weight of Sb,S,. 0.1616 0.1654 1.1174 1.1162 1.1158 3c Pb. Per Cent. Weight of Sb,S,. 81.62 81.17 Weight O f SnO,. 1.1557 1.1528 1.1550 ALLOY B. Weight of SnO,. 0.0805 0.0748 Sn. Per Cent. 24-45 24-01 24.36 Sn. Per Cent. 6.32 5-86 Method I. : Antimonyand tin separated as oxides. Method 11. : Antimony and tin separated as sulpho-salts. Method I. : Antimony and tin separated as oxides. Method 11. : Antimony and tin separated as sulpho-salts.In the second case, the sulphides of lead and copper (obtained by the separation of the antimony and tin as soluble sulpho-salts, as in Henz's method) were carefully washed with boiling water and flushed into a glass dish, treated with nitric acid and bromine, evaporated to dryness, and taken up with nitric acid and water and treated as in the first case. The results in Table F show conclusively that any separation depending on the solubility of the sulpho-salts is quite untrust- worthy when large quantities of lead are present. In fairness to Henz's method, it may be pointed out that it was only put forward as a method for the separation of antimony and tin in white metals, which do not contain much lead. The method is, * The high percentage of lead in these series is due to contamination of lead sulphate with stannic oxide.THE ANALYST.9 therefore, limited in its applicability. Furthermore, those alloys which are suitable for the Henz treatment give a precipitate of lead and copper sulphides, which is so slimy that it is filtered and washed only with extreme difficulty. Another point to which attention might be called from a commercial point of view is the expense of the 30 per cent. hydrogen peroxide used in the separation. The results given in Table F, besides showing the contamination of the lead sulphate obtained by Henz’s separation, also indicate that concordant results can easily be obtained by the procedure described in Fresenius. The exact details of the method vary considerably with different operators.We may say, however, in con- clusion, that the method, whether worked as described by Fresenius, or by any of the various modifications now favoured by analysts, remains the best, the most widely applicable, and certainly the quickest, of all the gravimetric methods we have examined. The use of the modified Soxhlet tube above described greatly lightens the burden of the manipulation of the antimony sulphide, and is there- fore to be recommended generally in any gravimetric estimations of antimony. ANALYTICAL LABORATORY, ROYAL COLLEGE OF SCIESCE, LOSDON, SOUTH KESSIKGTOS, S.W. DISCUSSION. Mr. F. 5. LLOYD asked if the authors could suggest any reason for the solubility of an alloy in liquids which were incapable of dissolving separately either of the metals of which the alloy was composed.Dr. RIDEAL said that his son had obtained in Classen’s laboratory satisfactory results with electrolytic methods very similar to those which the authors had used for the electrolytic separation of antimony and tin. Mr. HEHNER said that much of the asbestos now supplied was so freely soluble in acid as to be unsuitable for general use in analytical work. He had recently examined a number of samples of asbestos, and had found that, although some few were only soluble GO the extent of a fraction of 1 per cent. in warm hydrochloric acid, the greater number dissolved to 8 considerable extent. Mr. CHAPMAN thought it desirable to emphasise the fact that, although the method based on the separation by means of the sulpho-salts worked quite well when the proportion of lead was small, the results for lead were always too high in the case of alloys containing large proportions of lead and comparatively little antimony and tin.Dr. MORGAN said he was afraid he was not prepared to give any very definite answer to Mr. Lloyd’s question. Possibly, however, there was some kind of chemical combination between the metals of the alloy. Their experience had been the same with alloys of very varying composition. As to electrolytic methods, the experience mentioned by Dr. Rideal was the same as their own. I t would be seen that the fifteen results given in the paper for alloys containing tin and antimony were very near the truth. This, however, was only the case when the proportion of lead was small. They had tried a great many other specimens of asbestos, including the slaty-coloured kind, and had found that all dissolved to a large extent even in dilute10 THE ANALYST. acids.:’: It was for this reason that they had ventured to recommend the kind referred to, which was by far the best they had examined as regards being unaffected by acids and allowing of rapid filtration. It was rather expensive, costing 20 marks per 100 grams, but was well worth its price. They agreed with Mr. Chapman that Henz’s method did not work well with alloys containing large quantities of lead; and, indeed, this was stated by Henz, who had not put forward his method a8 applying to alloys of that kind. The fact that the insolubility of the tin and antimony sulphides was increased by the presence of a large quantity of lead sulphide, although known to analysts, was not often mentioned in the literature as a limitation of the sulphide separation of these metals. Mr. CHAPMAN said that he had only mentioned the question of the lead because in some textbooks the method was recommended as a standard laboratory method, without any mention of its limitations in this direction.

ISSN:0003-2654    

DOI:10.1039/AN9093400003

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

10 THE ANALYST. OIL FROM “ CARAPA GUYANENSIS” (“ CARAPA PROCERA,” D.C.). BY J. LEWKOWITSCH, PH.D. (Read at the Meeting, December 2, 1908.) IN a previous paper (ANALYST, 1908, 33,184) on “ Carapa Oil ” I pointed out the dj&- culties that surround the problem of correctly identifying the several species of Carapa, and I also described the oil obtained from the new species-Carapa gyaizdijlora. Through the kindness of Professor Dunstan, of the Imperial Institute, I received a considerable quantity of the seeds of C‘arapa guyanensis. I am informed that there is some confusion with regard to the botanical origin of these Carapa seeds. The seeds were sent from Sierra Leone as Carapa guyanemis, Aubl., apparently following a mistake in Oliver’s ‘‘ Flora of Tropical Africa.” The species described by Aublet was, however, Carapa guianensis, and this is confined to the West Indies and South America.It seems, therefore, probable that the nuts sent from Sierra Leone are derived from Carapa procera, D.C., of which C. guyanensis, Oliv., and C. guineeitsis, A. Juss., are synonyms. A large proportion of the kernels were mouldy ; hence in several lots of nuts, amounting to about 20 pounds each, the good kernels, bad kernels, and shells were determined quantitatively with the following result : ... Good kernels ... . , J ... 35.5 per cent. Bad kernels ... ... ... 27.0 ,) ,, Shells ... ... ... ... 37.5 ,, ,, ... ... The sound kernels yielded by extraction with ether 57.26 per cent. of oil, * In reply to queries as to the cornyosition of the quick-filtering white asbestos recommended by the authors, Mr.Cshen has since analysed thc substance, with the following result : SiO, 56.17, MgO 23’6, CaO 13’64 (FeO,Al,O,), 3‘11 per cent., with sniall amounts of MnO, Na,O, and H,O not determined. These numbers show that the material, although resembling glass-wool in texture, has the composition of a typical asbestos. Compare Dana’s “ Mineralogy,” fifth edition, p. 236.11 THE ANALYST. A large quantity of good kernels were comminuted in the manner simulating the operation on a large scale, and were pressed in the cold in a hydraulic press at a pressure of 150 atmospheres. A yield of 24 per cent. of oil was thus obtained. The pressed cakes were then broken up, comminuted, warmed to 150' F., and again expressed in the hot press at a pressure of 150 atmospheres.A quantity of hot pressed oil, amounting to 27 per cent. of the kernels, was obtained. The total amount of oil recovered from the kernels amounted to 46.7 per cent., as compared with 57-26 per cent. obtained by extraction with ether. The oil extracted with ether-the total oil-had the iodine value 75.09. The cold pressed and hot pressed oils were examined separately, and gave the following constants : Cold Pressed Oil. Specific gravity at 40" C. (water at Specific gravity at 15.5' C. (water at 40°C.=1) ... ... ... ... 0.9179 ... 15.5" C. = 1) ... ... ... Solidif ying-point ... ... ... 12O c. ... Melting-point ... ... ... ... 15-36' C. ... Saponification value . , . ... ... 197.1 ... Unsaponifiable matter ... ...... 1.51% ... Butyro-refractometer '( degrees . . . . . 54.5 ... ... 0.9272 ... Iodine value ... ... . I . ... 75-67 ... Reichert-Meissl value ... ... ... 3.53 ... Hot Pressed Oil. 0.9174 0.9327 14' C. 15-48' C. 196.4 71.25 3-14 2.04 % Insoluble Fatty Acids. Cold Pressed Hot Pressed Oil. Oil. Fatty acids + unsaponifiable , . . ... 95.13 ... 92.66 % Neutralisation value ... ... 192.4 ... 192.0 Mean molecular weight of the fatty acids ... ... ... ... ... 291.5 ... 292.1 Solidifying-point (Titer test) ... ... 35-45' C. ... 36-15' C. ... The insoluble fatty acids consisted of : ( 6 Liquid " acids (yielding ether-soluble ( 6 Solid " acids (yielding ether - in - Iodine value of solid fatty acids ... 16.56 ... 17-87 lead salts) ... ... ... ... 65.9 % ... 63.46 % soluble lead salts) ... ... 34.1 % ... 36.54 % ... Iodine value of liquid fatty acids ... 107.4 ... 108.0 Through the kindness of Dr. T. A. Henry, the oil was examined polarimetrically In contradistinction to the oil from The oil and the cakes have a very bitter taste, like all the corresponding products by Dr. Pickles in the Imperial Institute. Carapu, grandiJoru, the present oil does not contain any optically active substances. of the other Cctrupa species.

ISSN:0003-2654    

DOI:10.1039/AN9093400010

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

12 THE ANALYST. A RAPID METHOD FOR THE DETECTION AND ESTIMATION OF FORMALDEHYDE IN MILK. BY HERBERT S. SHREWSBURY, F.I.C., AND ARTHUR W. KNAPP, B.Sc., F.I.C. (Read at the Meeting, Decembey 2, 1908.) iMetlzod.-The reagent is made by mixing 0.1 C.C. of pure nitric acid (or 1.6 C.C. of normal nitric acid) with 100 C.C. of concentrated hydrochloric acid. To 5 C.C. of milk in a test-tube (about 18 ems. by 2 cms.) 10 C.C. of the freshly made reagent are added, the mixture shaken vigorously, and kept for ten minutes in a water-bath at a constant temperature of 50" C. The tube and its contents are then cooled rapidly to about 15" C. A violet colour shows the presence of formal- dehyde, and its intensity indicates the amount, which may be estimated by means of standards put on at the same time.If the colour obtained is deeper than that shown by 6 parts of formaldehyde per million of milk, it will be advisable for accurate estimations to use a dilution of the sample made with pure milk. In the following table it will be seen that the most delicate quantitative reaction is obtained with milks containing 0.2 to 6.0 parts of formaldehyde per million. LIMITS OF REACTION. Parts Formaldehyde per Million of Milk. 0 ... ... ... ... 0-1 ... ... ... ... 0.2 ... ... ... 1, 2, etc., to 6 ... ... 7, 8, 9, 10, 20, etc., to 80 ... 80 to 2,000 ... ... ... 2,000 to 10,000 ... ... 0.2, 0.3, etc:;'to 1.0 ... Appearance. Sixty-three samples were examined, and none showed Very faint heliotrope, scarcely distinguishable from Distinct pale heliotrope. Colours grade well.A difference of 0.3 part can be Each increase of one part showed a marked increase in Intensity of colour increases slightly. Decrease of colour. Two thousand parts give colour Gradual change of colour from violet to yellow. more than the faintest discoloration. blank. detected with certainty. intensity of colour. about equal to that given by three parts. Appearuiice gicen by Milks Free fi-onz Fo~maldehyde.--It has been stated that the Massachusetts State Board of Health (British Food Jou~nul, 1899, p. 208) had for two years been detecting and estimating formaldehyde in milk by adding hydro- chloric acid and a drop of ferric chloride to the milk, and heating the mixture to just below the boiling-point in a porcelain dish. Leonard and Smith (ANALYST, 1899, 24, 86) devised independently a similar method of estimation.Fisher pointed out (Zoc. cit.) that heavily borated milk also gave a violet colour. C. Amthor (Zeits. UnterszLch. Nahi.. Geimssiu., 1900, 3, 233-235 ; ANALYST, 1900, 25, 208) criticised this method, having obtained violet colours with milks containing neither formaldehyde nor boric acid, on heating with hydrochloric acid. These conflicting opinions led us to test by our method the following milks,THE ANALYST. 13 none of which contained formaldehyde : ( a ) Sixty-three fresh samples ; ( b ) milk containing 0.5 per cent. boric acid; (c) milk saturated with boric acid; (d) boiled milk ; (e) sour milk in all stages of decomposition. We did not obtain in any of these cases more than the faintest discoloration, the milk remaining practically white.A white blank is an obvious advantage, and cannot be obtained (1) if ferric chloride be used as an oxidising agent, or (2) if the reacting substances are heated to 100" C. There can be little doubt that the reaction is the same in all its essentials as that of the Hehner test, the chemistry of which has been described by 0. Rosen- heim (ANALYST, 1907, 32, 32). As Rosenheim found with sulphuric acid, so we find with hydrochloric acid, that the colour is not produced with milk proteins unless an oxidising agent and formaldehyde are present in certain ratios. Neither is the colour obtained unless the acid (a) is strong and (b) present in considerable con- centration. Thus no colour resulted with formalised milk, and a 0.1 per cent.solution of pure nitric acid in-(a) Pure acetic acid (milk 5 c.c., acetic acid 10 c.c.); ( b ) water (milk 5 c.c., water 10 c.c.) ; or with a 0.1 per cent. solution of ferric chloride in (c) normal sulphuric acid (milk 10 c.c., acid 7 c.c.) ; (d) normal hydrochloric acid (milk 10 c.c., acid 7 c.c.). Normal nitric acid alone, or a 1 per cent. solution of nitric acid in hydrochloric acid, gave the usual yellow colour yielded by proteins when oxidised with nitric acid. The uBe of a large excess of acid is advantageous, as it produces a homogeneous liquid. We have tried as oxidising agents in this reaction hydrogen peroxide, sodium arsenate, and ferric chloride, but tho colours produced were not so satisfactory as when nitric acid is used. We believe our method is the most delicate test for formaldehyde in milk, and we prefer it on this account to that described by one of us (Shrewsbury, ANALYST, 1907,32, 5), and also because it is rapid and gives white blanks and pure colours.We wish to state that the above work has been greatly facilitated by the kind- ness of the Birmingham Health Committee in permitting us, the assistants of the Public Analyst, to prosecute research in the Municipal Laboratory. DISCUSSION. Mr. C. G. MOOR asked whether such dyes as might be sometimes used in commercial milk would have any effect on this reaction. In determining the fat in milk by centrifugal methods, one often obtained, on the addition of acid, a strong coloration which might be due to colouring matters. Mr. CHAPMAN said that if a sample gave a colour reaction with acid, one probably would not attach too much importance to the indications of this test for formaldehyde, It would be noted, however, that the authors had obtained perfect blanks with no fewer than sixty-three samples, and it seemed only reasonable to suppose that of so large a number some might have been artificially coloured.Mr. W. PARTRIDGE asked how the quantities of formaldehyde added to the tubes shown were measured--i.e., whether the ordinary formalin solution was distilled or standardised in any way, or whether it was simply assumed to contain 40 per cent, of formaldehyde. Mr. F. J. LLOYD asked how long it remained possible to obtain the reaction after the formaldehyde had been added.14 THE ANALYST.Dr. MONIER-WILLIAMS remarked that Hehner had shown that formaldehyde when added t o milk gradually disappeared, and the coloration obtained at any particular moment would be due merely to the formaldehyde that had not yet disappeared. Mr. LLOYD asked whether there was any hope of being able to find the formaldehyde after it had entered into combination with the casein. Dr. LESSING drew attention to Sorensen’s work on the action of formaldehyde on amino-acids, which might furnish some explanation for the disappearance of formaldehyde in milk, It is conceivable that the formaldehyde might combine with the amino-group in such a way that it could possibly continue to produce characteristic reaction. The authors replied that the standards were made from a solution of 1 part formaldehyde by weight in 1,000 parts of water, standardised by the iodine method. They consider that the dyes commonly used in milk would not interfere with the formaldehyde reaction. Formalised milk (unlike dyed milk) did not give a colour with the reagent in the cold in less than twenty-four hours, Some dyed samples were included in the milks tested. The faint tints produced in these were different from, and very much paler than, the colour obtained when 1 part formaldehyde per million was present. 0. Rosenheim (ANALYST, 1907, 32, 107) showed that the compound derived from casein and formaldehyde gave the usual violet colour with sulphuric acid and an oxidising agent. Formalised milk fails to give the Hehner reaction after a certain time, SO that apparently the formaldehyde undergoes other changes.

ISSN:0003-2654    

DOI:10.1039/AN9093400012

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

14 THE ANALYST. THE DETERMINATION OF ALDEHYDES IN OIL OF LEMON. BY ALEX. H. BENNETT. THE estimation of citral in lemon oil is a subject which has attracted a good deal of attention, and a number of methods have been suggested for the purpose, none of which, however, have hitherto obtained general acceptance. The process at present to be described is ~t slight modification of one originally put forward by Walther (Plzarm. Centralb., 1899, 40, SZl), and depending on the reaction between the aldehyde and hydroxylamine. In this process the lemon oil was heated in alcoholic solution under a reflux condenser with a sufficient excess of a 5 per cent. solution of hydroxylamine hydrochloride in alcohol, with the addition of 0-5 to 1.0 gram of sodium bicarbonate, which serves to neutralise the hydrochloric acid liberated by the action.The excess of hydroxylamine remaining at the end of the reaction is titrated, and comparison with a blank experiment gives the amount which has entered into combination with the citral. Messrs. Schimmel and Co. (Semi-Annual Reports, April, 1900) criticised this method on the ground that the carbon dioxide evolved carries off hydroxylamine, which thus appears as if it had entered into combination with citral, giving rise, therefore, to results which are too high, and which vary according to the excess of bicarbonate, the time and rate of boiling, and other conditions.THE ANALYST. 15 To overcome this objection I have, instead of using bicarbonate, proceeded by the addition, to the solution of the hydrochloride, of alcoholic soda or potash, in quantity sufficient to liberate an amount of hydroxylamine in excess of that which would be required to combine with the citral present, but not to complete neutralisa- tion of the acid of the hydrochloride, Such a partially neutralised solution can be boiled under a reflux condenser without any loss of the base, as is shown by the following experiments : Twenty C.C.of a solution of hydroxylamine hydrochloride in 80 per cent. alcohol, exactly neutralised to phenolphthalein with sodium hydrate, required for retitration (after diluting with water, and using methyl orange as the indicator) 19.9 C.C. of sodium hydrate and heated under a reflux condenser for half an hour, and an hour and a half respectively. After cooling, diluting with water, and completing the neutralisation to phenol- phthalein, each required 19-9 C.C.of : sulphuric acid for the retitration. sulphuric acid. Two similar quantities were each treated with 8 C.C. The actual analysis is conducted as follows : Twenty C.C. of lemon oil are mixed with 20 C.C. of a solution of hydroxylamine hydrochloride in 80 per cent. alcohol, and to the mixture is added about 8 C.C. of alcoholic potash and 20 C.C. of strong alcohol (which is sufficient to procure complete solution when hot). The mixture is boiled gently under a reflux condenser for half an hour, and then allowed to cool. The condenser is washed down, and the contents of the flask diluted with about 250 C.C. of water, and neutralised to phenolphthalein. The liquid is then titrated with sulphuric acid, using methyl orange as indicator.The number of c.c.'s of acid required, subtracted from the number used in a blank experiment, in which no lemon oil is present, gives the amount of hydroxylamine which has entered into reaction with the citral, and multiplied by 0.076 gives the weight of citral. When the titration to methyl orange is performed in the usual way with addition of a drop of the indicator to the solution, the end point is often not very satisfactory. I find that much sharper results are obtained by making use of drops of a very dilute aqueous solution of methyl orange scattered on a white plate. When drops of the solution which is being titrated are brought into contact with these the change of colour when neutralisation is complete is well marked. EXPERIMENTS WITH KNOWN MATERIALS.The (' pure " citral obtained from Kahlbaum was optically inactive, and had a specific gravity of 0.8903 at 25" C. When agitated with sodium sulphite solution 8 small residue remained unabsorbed, which, extracted with ether, amounted to 4 par cent. of the citral taken. Portions analysed by the foregoing process gave the following results : Citral Taken. Found. Per Cent. 0.958 gram ... ... 0.919 ... ... 95.7 1-088 ,, ... ... 1.049 ... ... 96.4 0.711 ,, ... ... 0.676 ... ... 95.1 0.935 ,, ... ... 0-889 ... ... 95.1 0.57'7 ,, ... ... 0.551 ... ... 95.516 THE ANALYST, 10.475 grams of this citral were dissolved in purified terpenes and diluted to One hundred C.C. of this solution would therefore contain 5.72 grams of the 175 C.C.aldehyde. Four determinations were made, using 20 C.C. and 10 C.C. of the solution. Found, 5.70, 5.72, 5-90, and 5.93 grams per 100 C.C. A sample of lemon oil was found by this method to contain 4.05 per cent. citral, To 50 C.C. of the essence, citral was added so as to give Found, 6-55 and 6.60 grams Mean, 5.81. or 3.45 grams per 100 C.C. a mixture calculated to contain 6.7 grams per 100 C.C. per 100 C.C. THE RESULTS WITH ESSENCE OF LEMON. A large number of samples have been examined by this process during the past season, and the results obtained lie almost entirely between the limits of 4 to 5 per cent. As a general rule, it may be said that the oils from the eastern part of the island show a somewhat higher percentage of aldehyde than those from the Palermo district, which seldom exceed 4.2 to 4.5 per cent., and also that the higher results are usually found in the essences made during the earlier part of the season-that is, UP to March.Whether the aldehyde content of an essence actually diminishes during storage is a point that I hope to determine during the coming season. The samples here referred to were ordinary commercial samples received in the course of practice, and were in all cases examined by fractional distillation and otherwise, but I have been able also to have a few samples prepared directly from the fruit under my own observation. The lemons were brought from the different districts mentioned, and the results found were as follows. (For the facilities for preparing these samples I am indebted to Messrs.Bush and Co., through the courtesy of Mr. Lewis Sofio.) Lemons from Barcelona, ... ... 497 per cent. ,, ,, Cctlabria, ... ... 4.6 ,, 8 ) ,, Messina ... ... 5.2 ,, ) ¶ ), Syracuse ... ... 4.3 ,, The last result is no doubt exceptionally high, though it was approached by a few other samples during the season. It is evident that a fair amount of variation is possible among genuine samples ; and on the experience of only one season it would be inadvisable to suggest any limits, though by comparison with the results of other methods I think that the above-mentioned figures-4 to 5 per cent.-will probably be found to include almost all pure essences. A few experiments have been made with previous concentration of the lemon oil by distillation under a pressure of 15 to 20 mm., as in the method of Burgess and Child (Jounz.Xoc. Chem. Ind., 1901, 20, 1176)-i.e., from 100 C.C. of oil 90 C.C. are distilled off, using a fractionating flask with three bulbs, and the residue, amounting to 7 or 8 c.c., is distilled with steam, and the citral determined in the distillate. The results found with hydroxylamine agree fairly well with those obtained when the citral is absorbed by means of sodium sulphite (exact agreement is hardly to be expected). I n one instance, 8 c.c. of steam distillate showed 40 per cent. aldehydeTHE ANALYST. 17 by absorption, and 38.7 per cent. by the hydroxylamine test. This last figure was equivalent to 3.2 per cent., calculated on the original oil, which by direct analysis, without concentration, had given 4.7 per cent, Very appreciable quantities of citral, however, are found in the terpenes of the distillate, as is shown in the following experiment : 7.5 grams of citral were dissolved in purified terpenes, and diluted to 150 C.C.Calculated citral, 4.8 grams per 100 C.C. Found by hydroxylamine test, 4.77 and 4.94. One hundred C.C. were distilled as above. Even the first 10 per cent. showed citral equal to 0.17 gram, and the following 80 C.C. were found to contain 1:4 grams ; or, altogether, 1-57 grams, or 1.8 per cent. I n this experiment the steam distillation was lost, but in another similar one I found : I n first 10 per cent. distilled ... ... 0.11 gram citral. I n 80 per cent. distilled ... ... 1 18 grams ,, I n steam distillate ...... ... ... 3.03 ,, ,, ... Total ... ... ... 4.32 I t is evident, therefore, that the results obtained in this way, though comparable with one another, and valuable to the manufacturer of terpeneless oils, are consider- ably below the truth. My thanks are due to my assistant, Mr. 0. J. D. Thomas, for carrying out, many of the analyses by this method. MEYSINA. DISCUSSION. Mr. CHA~WAN said that the subject of this paper was of great practical importance, and it was a matter for congratulation that the Sicilian analysts were now coming into line with the general practice of analysts irl other parts of Europe. Only a very few years ago the methods adopted in Sicily for the analysis of lemon oil gave results in the neighbourhood of 7 or 8 per cent'. of citral, whereas manufacturers complained that do what they might they could not obtain more than 4 per cent, He might point out that Mr. H. E. Burgess had, some few years ago, called attention to the necessity of varying the amount of bicarbonate of soda used in the hydroxylamine method; but no doubt the process as recommended by the author was better, and he (Mr. Chapman) thought they were much indebted to Mr. Bennett for sending them this communication. Mr. L. MYDDELTONASH said that some two or three years ago a Messina analyst had admitted to him in conversation that he knew that the citral in lemon oil never reached 7 per cent. The growers, howevar, were accustoined to b3 paid on the unit percentages shown by the particular method in question, and for that reason it was retained, although it was known to be incorrect. Mr. CHAPMAN said that there would have been no objection to that if certain of the Messina Analysts had not contended that the results were actually correct.

ISSN:0003-2654    

DOI:10.1039/AN9093400014

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. The Detection of Benzoic Acid in Fats, and especially in Butter. L. Robin. (Ann. de Chim. Anal. AppZ., 1908, 13, 431-433.)-The following method is capable of detecting with certainty 3 mgms. of sodium benzoate in 25 grams of butter : That quantity of the melted butter-fat is shaken with a solution of 0.4 to 0.5 gram of sodium bicarbonate in 50 C.C. of water and 15 C.C. of 95 per cent. alcohol, and the whole allowed to stand for ten minutes. The alcoholic layer (which should be alkaline to turmeric) is then drawn off, acidified with 7 or 8 drops of sulphuric or hydrochloric acid, and heated just to the boiling-point, after which it is shaken with a little talc and filtered. The cold filtrate is extracted in a separating funnelTHE ANALYST.19 with 40 C.C. of ether, and the ethereal extract washed once with a mixture of 20 C.C. of water, 5 C.C. of 95 per cent. alcohol, and 0-2 to 0.3 gram of sodium bicarbonate. This alkaline alcoholic extract is evaporated on the water-bath, and the residue will contain the sodium benzoate. To identify the benzoic acid, the residue is cautiously heated with a mixture of 5 C.C. of concentrated sulphuric acid and 10 drops of fuming nitric acid until white vapours appear, the liquid being then poured into 50 C.C. of water containing a fragment of turmeric paper. A yellow coloration indicates benxoic acid, and its presence may be confirmed by rendering the yellow liquid alkaline with ammonia, and adding ammonium hydrosulphide drop by drop, with shaking after each addition.When benzoic acid is present, the colour changes, after the addition of a few drops, from yellow to reddish-orange, the interlsity of the latter coloration depending upon the quantity of the acid. C. A. 31. Estimation of Fat in Chocolates by Means of Chloral Alcoholate. A. Kreutz. (Zeits. Unterazich. Nahr. Genussm., 1908, 16, 584-586.)-The method described previously for the estimation of fat in cocoa (ANALYST, 1908,33,320) may be applied to the estimation of fat in chocolates. From 2 to 3 grams of the sample are used for the estimation, and it is recommended that, after evaporating the ether from the extract obtained as described in the case of cocoa, the chloral alcoholate be removed by heating under reduced pressure at a temperature of about 75" C.The residue obtained is treated with carbon tetrachloride, to dissolve the fat, and the solution is filtered, to separate a little theobromine and colouring matter which arc present. The filtrate is then evaporated, and the residue of fat weighed, after being dried at a temperature of from 100" to 105" C. w. P. s. Colour Reaction of some Essential Oils, with Special Reference to the Examination of the Fat obtained from Flavoured Chocolates. R. Reich. (Zeits. Untersuch. Nahr. Genussm., 1908, 16, 452-459.) -It has been shown by Gerber (ANALYST, 1907, 32, 90) that certain flavouring materials such as are added to chocolates give colorations with the reagents which are employed for detecting the presence of sesame oil, and that on this account the detection of the latter in chocolates is rendered more difhult. The author has systematically examined a number of essential oils, etc., as regards their behaviour towards these reagents, and the following are the results of his experiments : Oil of cloves contains furfural, and gives a, red coloration when treated with sesame oil and hydrochloric acid; oil of cloves, oil of pimento, and oil of bay, which all contain eugenol, give red or yellowish-red colours with stannous chloride and with vanillin dissolved in hydro- chloric acid, as well as when heated with hydrochloric acid alone.When shaken with sesame oil and hydrochloric acid, cinnamic aldehyde gives a violet-red, vanillin a blue-violet, and benzaldehyde a yellowish-red coloration ; oil of cinnamon (Ceylon) and oil of cassia give the same colour reaction as does cinnamic aldehyde, and this aldehyde yields a permanent olive-green coloration when shaken with stannous chloride solution.These reactions must be taken into account when testing the fat obtained from chocolates for sesame oil. If the fat contains -sesame oil as well as traces of cinnamic aldehyde or vanillin it will give a violet-red coloration with hydro-20 THE ANALYST. chloric acid. A red coloration is produced when thymol is mixed with vanillin and hydrochloric acid, and oil of caraway and its constituent-carvone-give a similar reaction. Camphor and menthol, and those essential oils which contain terpenes- namely, oils of peppermint, lemon, ginger, eucalyptus, and turpentine-when treated with hydrochloric acid and vanillin, give red, violet-green, green, or blue-green colora- tions ; on warming, these colours change to blue or blue-violet.w. P. s. The Theobromine-Content of Cocoa and a New Method for Estimating the Same. A. Kreutz. (Zeits. U?ztewxh. Nahr. Genussm., 1908, 16, 579-584.)- On estimating the fat in cocoa by the method described previously (ANALYST, 1908, 33,320), it was noticed that the fat contained a crystalline substance which was sub- sequently proved to be theobromine. Further experiments showed that a portion of the theobromine existing in cocoa is extracted along with the fat, whilst the remainder, probably present as a glucoside, is only obtained after subjecting the cocoa to hydrolysis. The method proposed below for estimating theobromine is only of actual use for ascertaining the total amount of theobromine in cocoa, as experimental evidence is adduced that it is impossible to separate exactly the free theobromine from that portion of the alkaloid existing as a, glucoside. The details of the method are: From 1.5 to 2.0 grams of the sample are treated with chloral alcoholate as described previously (Zoc.cit.), and the residue of fat and theobromine is weighed. The fat is then dissolved in carbon tetrachloride (in which theobromine is quite insoluble), and the solution is filtered. The solvent is evaporated, and the residue of fat is reweighed. The diff’erence between the two weighings gives the amount of theobromine. The residue of cocoa obtained in this part of the process is dried and boiled under a reflux condenser with about 50 C.C.of 4 per cent. sulphuric acid for forty-five minutes. The hot solution is then neutralised by the addition of moist barium carbonate, and the mixture evaporated to dryness. The residue is ground up with clean sand and extracted with chloroform for five hours in a Soxhlet apparatus, the chloroform extract being afterwards evaporated and the residue of theobromine weighed. The following quantities of total theobromine were found in various samples of cocoa : Schaal’s, 3-73 to 3-82 per cent. ; Reichardt’s, 3-55 to 3-85 per cent, ; van Routen’s, 1.99 to 2.23 per cent. ; Stollwerk’s, 3.18 to 3.48 per cent. ; and Suchard’s, 2.63 to 2.92 per cent. w. P. s. Estimation of Essential Oils in Spices, etc.R. Reich. (Zeits. Untersuch. Nahr. Qenussm., 1908, 16, 497-509.)-The ordinary method of estimating essential oils in spices by steam-distilling the latter, salting out the oil from the distillate, dissolving the oil in a suitable solvent, and evaporating the solution, fail8 to give accurate results, owing to the difficulty of exactly ascertaining the point at which the whole of the solvent has been removed, as further drying beyond this point results in loss of the volatile essential oils. Mann has proposed (Archiv. Pharm., 1902,240, 155) a method in which the ethereal solution of the oil is placed in a flask through which a current of air is aspirated; the air leaving the flask is passed over calcium chloride, and then through a fine platinum jet against the top of a small Bunsen flame, and, when the air ceases to give a luminous cone by its burning, the dryingTHE ANALYST.21 operation is stopped and the residue of oil weighed. The author now gives a modi- fication of Mann's process. The solution of the essential oil in ether, pentane, or rhigolene (a petroleum spirit fraction boiling at 20" to 30" C.) is placed in a flask, and the bulk of the solvent is evaporated as described by Mann. A drop of isopropyl chloride is then added to the contents of the flask, and the current of air continued until the air leaving the flask no longer gives a green flame when directed through a platinum jet against a piece of copper gauze heated to dull redness by means of a small Bunsen flame. The green colour of the flame persists as long as there is the least trace of isopropyl chloride (or solvent) remaining in the flask, and is much more visible than the luminous cone mentioned by Mann.Results of estimations are given showing that the method is trustworthy for the estimation of cinnamic alde- hyde, eugenol, menthol, thymol, camphor, carvone, and the essential oils of cassia, cinnamon, cloves, pimento, peppermint, aniseed, and ginger. In the case of oils of caraway (total), lemon, eucalyptus, and turpentine, the results obtained are un- satisfactory owing to the presence of very volatile compounds (terpenes). w. P, s. Notes on the Mace of Commerce. E. M. Holmes. (Pharm. Joz~r~t., 1908, 81,652.)-There are three kinds of mace found in commerce in this country-namely, genuine or Banda mace, which is the arillus of the fruit of Mt-+stica fragrans; Bombay mace, from M.Malabarica ; and Macaasar mace, from ill. argentea. Genuine mace, when broken across and examined with a hand-lens, appears on the broken surface oily but uniform, the oil-cells not being easily distinguishable. It has a characteristic flavour, resembling, but distinct from, that of nutmeg, and is scarcely acrid. The surface of Bombay mace, when broken across, shows under similar conditions, on its inner edge, a projecting, slightly transparent membrane, and the oil-cells are distinctly recognisable as dark-reddish points forming an irregular ring near the surface. Bombay mace has a sweetish and somewhat mucilaginous taste, with a faint flavour having scarcely any pungency. Macassar mace has a flavour nearly resembling nutmeg but somewhat sassafras-like, and is distinctly acrid, this characteristic being alone sufficient for its recognition.The transverse surface of Macassar mace is oily like that of true mace, but the oil- cells are distinguishable in a good light, being apparently larger than those of M. fragrans. According to Soltsien (1894), Bombay mace, after exhaustion with petroleum- ether, yields about 30 per cent. of matter to ether, while genuine mace only yields 3-5 per cent. Schneider found (Year-Book Pharm., 1897, 156) that the colouring matter of Bombay mace dissolves in caustic potash solution with an orange-red colour, changed to yellow by sulphuric acid (50 per cent.), with partial precipitation of the colouring matter. Hefelmann (Pharnz.Zeit., 1891, 122) showed that the adulteration of mace with the Bombay*variety may be detected by boiliug the sample with alcohol and filtering through filter-paper. The edge of the paper is stained red in the presence of the adulterant, and if this be present only i n small amount the colour may not appear until the filter-paper is dried. If basic lead acetate solution is added to the alcoholic filtrate, a white turbidity is obtained in the case of genuine22 THE ANALYST* mace, but a red precipitate if Bombay mace be present. Turmeric gives a similar reaction; but a strip of white filter-paper moistened with the alcoholic solution, and then with a cold saturated solution of boric acid, will become orange-brown in the case of turmeric, remaining unchanged in the case of Bombay mace.A. R. T. The Detection of Hydrogen Peroxide in Milk. W. P. Wilkinson and E. R. C. Peters. (Zeits. Unterszich. Nahr. Gemssm., 1908, 16, 515-517.)-The authors have investigated a test proposed by Feder, which depends on the formation of a blue-violet coloration when milk containing hydrogen peroxide is heated with hydrochloric acid after the addition of a little formaldehyde. They find that the intensity of the coloration obtained is not only dependent on the actual quantities of hydrogen peroxide and formaldehyde present, but also on the proportion which the quantities of these two substances bear to one another. The results of. the experiments given show that the strongest reaction is obtained when about 0.005 per cent.of hydrogen peroxide and from 0.004 to 0.013 per cent, of formaldehyde are present. Traces of other substances, such as ferric salts, nitrates, etc., also give the reaction, and a sample of milk which gives a coloration with the test does not, therefore, necessarily contain hydrogen peroxide. The reaction recommended recently by the authors (ANALYST, 1908, 33, 401) for the detection of hydrogen peroxide is capable of detecting as little as 0.001 per cent. of this substance. Ferric salts and nitrates do not give any coloration. W. P. S. Colorimetric Estimation of Formaldehyde in Milk. E. W. T. Jones. (Chem. News, 1908, 98, 247.)--The method is based upon the well-known blue colour reaction obtained when milk containing formaldehyde is warmed with hydro- chloric acid containing a trace of iron.The acid reagent is prepared by dissolving 0.25 gram of pure iron wire in hydrochloric acid, the solution oxidised with nitric acid and the iron precipitated with ammonia, and the washed precipitate dissolved in 500 C.C. of strong hydrochloric acid. A standard solution of formaldehyde is made by diluting 1 C.C. of “ formalin” (40 per cent. solution of formaldehyde) to 1 litre with water; 0.1 C.C. of this solution added to 10 C.C. of milk gives a product con- taining 1 part of “formalin” in 100,000 (or 1 part of formaldehyde in 250,000 parts of milk). To make an estimation, 10 C.C. of the suspected milk, contained in a large test- tube (1” x 6’7, are treated with 10 C.C. of the acid reagent, while into each of two similar tubes 10 C.C.of pure milk are placed, and to one of these 0.1 c.c., and to the other 0.2 c.c., of the dilute standard “formalin ” solution is added, together with 10 C.C. of the acid reagent in each case. The contents of the three tubes are well mixed, and then placed in a water-bath at 90” C., which is subsequently kept at a temperature of 80” to 85” C. for twenty to twenty-five minutes. To each tube 30 C.C. of cold water are added, the mixture shaken, cooled, and filtered, the residue washed with about 10 C.C. of water, and the filtrates made up to 100 C.C. in each case. The colours are then compared in Nessler glasses in the usual manner. If the colour shown in the ‘‘ sample ” filtrate be darker than that given by the 0.1 C.C. standard,THE ANALYST. Alcohol, by Volume, per Cent.23 Extract, per Cent. it is better to dilute the 0.2 C.C. standard. The colour given by the lower standard is not so pure as that obtained by diluting the stronger standard to the strength of the lower one. The sample and the standards must be submitted to exactly the same conditions side by side. A. R. T. Total Acids, per Cent. The Composition of Certain Wines from the South of France. J. Fiehe. (Chem. Zezt., 1908, 32, 1105-1106.)-For many years past the genuine character of certain French wines has been called in question by German chemists on account of their abnormal values for total extract and free tartaric acid. Apart from the fact that many of the wines contain less than the lowest proportion of extract regarded as genuine in Germany, most of them also contain a considerable amount of free tartaric acid, According to German regulations the free tartaric acid in wines containing not more than 0.8 gram of total acids in 100 C.C.should not, as a rule, exceed one-fifth to one-sixth of the total non-volatile acids; in wines containing more than 0.8 gram of total acids per 100 C.C. the proportion of free tartaric may be higher. French chemists, on the other hand, have repeatedly asserted that these wines from the South of France are genuine, and that the free tartaric acid may amount to about 2.0 grams per litre. I n order to obtain complete certainty on the points in dispute, the author has examined the wines from grapes, grown near Narbonne, and shows that the frequently high proportion of free tartaric acid must be attributed to the conditions of the soil, and not to any addition of that acid.The following results are typical of those obtained, the amounts of total and free tartaric acid having been estimated by the official German method of Halenske and Moslinger (Zeit. Anal. Non- Total Volatile Sugar, Tartaric Acids, per Acid, per Cent. Cent. per Cent. Chem, 1905, 34, 279) : 7.7 5.2 9.5 9.6 11.0 Variety of Grapes. 1.37 1'9 1.90 2.34 1.55 Arariioii : 1907 .. 1907 .. Csrignari : 1907 .. 1907 .. Bourret : 1907 .. 0.675 0.937 0.675 0.825 0.487 Colour. 0.570 0*100 0'450 0*8!!5 0'120 0.67 0.584 0.132 0.270 0.700 0.11 0.375 0'427 0.10 0.150 Wliite Red l \ l i t c lied Whit c Specific Gravity. 0,9954 1.0014 0.9952 0.9973 0.9938 Ash, Per Cent. 0'196 0'530 0-214 0.330 0.354 Alka- linity tf Ash in C.C.N - K ~ H . 1.55 2.75 2 .OO 2'25 2.05 c. A. ~ Free Tar - taric Acid ~ Per Cent. 0.218 0.263 0.084 0.037 0'023 M. The Detection of Artificial Invert Sugar in Wines by Means of the Resorcinol-Hydrochloric Acid Reaction. A. Kickton. (Zeits. Unterszuh. Nclhr. Geizussnz., 1908, 16, 574-579.)-The reaction described by Fiehe (ANALYST, 1908, 33, 397) for the detection of invert sugar in honey cannot be applied generally to the detection of this sugar in wines. In the first place, the decomposition product which gives the coloration is considerably affected by fermentation. Secondly, sweet wines such as port, sherry, tokay, malaga, etc., of undoubted genuineness,24 THE ANALYST. All Samples. Maximum ... Minimum ... Average ...invariably give a positive reaction with the test. This is proba,bly due to the presence of caramel and other substances which are known to give a red coloration when treated with resorcinol-hydrochloric acid, and also to the fact that this class of wine is frequently made from evaporated grape-juice. w. P. s. Commercial Sicilian Sumac. F. P. Veitch and B. J. Howard. (BzLlZ. No. 117, Burecu of Chemistry, Uizited States De?:anhmt of Agriczdtzm, 1‘308, September 12; through Jozmt. Soc. Chew,. I d . , 1908, 27, 1164.)-The leaf of BlzzLs coriaria, or Sicilian mountain sumac ( I ( masculmo ’!), contains from 25 to 35 per cent. of tannin, and suffers much adulteration with stems and with lower grade and darker coloured substances, the chief of these being the leaf of Pistacia Zciztiscus (“ lentisco 7 7 ) , which contains 12 to 20 per cent. of a catechol-tannin, which darkens on exposure to air.The leaves of the following are less generally employed as adulterants : CoTiaria nzyrtzfolia (‘( stinco ”), Tawzarie Afiicaiaa ( b 4 brusca ”), Ailantlzus qladzdosn, and Vitis vinifwu (grape-vine). The samples of commercial Sicilian sumac examined gave the following results on analysis : Tintoinetre Reading. Soluble Non- Available Colour Extract. Tannins. Tannins. o.5 per Cent. Solution. Sand’ Moisture. Ash. Red. Yellow. 9-46 10.95 3.05 55.4 22-7 35.1 11-2 27.8 6.34 6-12 0.28 41.8 17.1 19.6 0.8 4-7 7-79 8.18 1-41 48.4 19.5 28.8 3.1 10.7 33.3 11.2 27-8 The percentage of available tannin and the colour of the pure and adulterated samples are shown in the following table.I t will be noticed that the adulterated sumacs contained on the average 2.2 per cent. less tannin than the general average of all the samples, indicating the presence of at least 30 per cent. of ‘‘ lentiscus ” : 19.6 26.6 1.9 4.1 5.6 11.8 Available tannins, per cent. Colour in 0.5 per cent. Red ... ... ... Yellow ... ... solution : Maximum 35-1 3.5 12.8 Pure Sumac. Minimum. 27.4 0.8 4.7 Average. 31.9 2.1 9.4 Adulterated Samples. Maximum. Minimum. Average. I 1 ii number of commercial samples contained an excess of sumac stems, but as the average tannin-content of these samples was 29.9 per cent., the stems are not added in such large quantities as the b ( lentiscus.” The colours of the dry sample and of the aqueous extract are distinctly darker i n adulterated specimens.THE ANALYSTo 25 The microscopical examination of the leaf is best carried out as follows: A small quantity of the sample is placed on a microscope slide with 2 or 3 drops of chloral hydrate solution (150 grams in 100 C.C.water), the mixture gently heated to boiling, and kept at that temperature for one minute, the chloral hydrate being replaced during the heating if necessary. The sample is allowed to cool, and then covered with a cover-glass, when it is ready for examination; or a portion of the powdered sample is slowly boiled with a few C.C. of chloral hydrate solution for two or three minutes, the mixture allowed to stand for a few minutes, and a little of the deposit then removed with a pipette, and mounted on a slide in the usual way.A. R. T. The Estimation of Succinic Acid in Fermented Liquids. E. Pozzi- Escot. ( A m . de. Chirn. Anal. AppZ., 1908, 13, 439-440.)--8 known volume of the liquid is treated with gelatin to remove tannin and colouring matters, then neutralised with ammonia, and treated with a large excess of acetic acid and with barium chloride to precipitate oxalic and other acids. The filtrate and washings are heated to boiling-point, and treated with a considerable excess of lead acetate, which precipitates albuminous substances, phosphates, and tartaric and citric acids, leaving malic and succinic acids in solution. The precipitate is washed with water rendered faintly acid with acetic acid, and the filtrate and washings treated with hydrogen sulphide. The precipitated lead sulphide is separated, and the filtrate boiled to expel the excess of hydrogen sulphide. I t is next acidified with sulphuric acid, and treated while boiling with potassium permanganate until the colour persists for at least five minutes. Under these conditions the malic acid and any residual traces of tartaric acid are completely oxidised. The boiling solution is now decolorised by adding a little potassium bisulphite, and the sulphuric acid precipitated with barium chloride. The filtrate is concentrated, rendered slightly alkaline with ammonia, and treated with an excess of an alcoholic solution of bariurn bromide, and with three times its volume of 95 per cent. alcohol. The precipitated barium succinate is collected, washed with 60 per cent. alcohol, and calcined in a muffle, and the residue of barium carbonate treated with a known excess of hydrochloric acid, the excess being subsequently titrated. The number of C.C. of hydrochloric acid consumed by the barium carbonate, multiplied by the factor 0.0059, gives the quantity of succinic acid in the sample of the original liquid. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN909340018b

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

THE ANALYSTo 25 BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. The Detection of Bile Acids by Means of Rhamnose. C. Neuberg. (Biochenz. Zeits., 1908, 14, 349-350.)-The author points out that the reaction described by Jolles (ANALYST, 1908, 33, 430) had been mentioned previously by Rauchwerger and himself (Chem. Centralbl., 1904, 2, 1434). I t was there shown that the reaction is also obtained with substances other than bile acids. Aromatic compounds (terpenes) occurring in urine give a green fluorescence when treated with rhamnose and sulphuric acid, and cholesterol gives a red coloration. The reaction w. P. s. is not, therefore, characteristic of bile acids.26 THE ANALYST. The Spectroscopical Identification of Blood-Stains on Coloured Fabrics. S. Wertogradow. (Westn. Obsch. Gigieni, 1908, 44, 1083 ; through Chem.%?it. Rep., 1908, 32, 582.)-The blood-stains may be readily dissolved by a 10 per cent.. solution of sodium hydroxide, and although the dyestuff from most coloured fabrics is simultaneously removed, the sharp spectrum of hzemochrornogen will appear more clearly than the spectrum of the dyestuff. A five per cent. solution of ammonia is also a good solvent, but also dissolves the dyestuff, though not to the same extent as sodium hydroxide solution. The spectrum of haemoglobin and of hzemochromogen may be clearly observed in a solution thus obtained, the one compound being readily transformed into the other. Blood-stains dissolved in glacial acetic acid give a less pronounced spectrum of hzematin, and this solvent is less suitable than the two preceding in the case of coloured materials.In the autbor's opinion the hEmato- porphyrin test with concentrated sulphuric acid is not sufficiently reliable. The best solvent for the stains is water in the presence of a current of carbon dioxide, for the dyestuff is but seldom extracted at the same time. C. A. &I. Excretion of Creatinine in Man. C. J. C. van Hoogenhuyze and H. Verploegh. (Zeits. physioZ. Chenz., 1908, 57, 161-266.)--As the result of a lengthy investigation, the authors confirm the conclusions arrived at by other workers that, whilst creatinine is converted into creatine in the liver, the latter organ is, in certain cases, capable of transforming creatinine from creatine. When the liver is largely destroyed by cancer, considerable quantities of creatine, instead of creatinine, are found in the urine.Fevers and hunger decrease the activity of the liver, and cause creatine to be excreted in the urine. Creatinine is never found in healthy tissues and blood, as it is removed completely and quickly by the kidneys. The method employed in estimating creatinine in urine was that recommended by Folin ; for the inversion of the creatine, the urine was heated for three hours with twice its volume of hydrochloric acid (cf. ANALYST, 1907, 32, 48). W. P. s. A Method of Determining the Degree of Bacterial Contamination in Milk by Means of Indigo Carmine. J. W. Winogradow. (Farmax. Jow., 1908, 47, 903; through Chent. Zeit. Bep., 1908, 32, 565.)--Five drops of a, 0.1 per cent. solution of indigo carmine are shaken with 100 C.C.of milk in a stoppered wide-necked flask, which the milk completely fills. When viewed by ordinary diffused light the milk then has a bluish tint, but in the presence of anaerobic bacteria, the colour gradually disappears. Milk that has been kept without any special precautions only retains the coloration for a few hours. If, however, the hands of the milker and the udder of the cow are washed before milking, and the vessels in which the milk is kept are perfectly clean, the colour may persist for forty- eight hours at 15' C. before bacterial reduction of the indigo carmine is complete. Vaudin gives as the minimum duration of the colour in milk fit for use : Twelve hours at 15" C. ; eight hours at 15" to 20' C. ; and four hours at temperatures above 20" C. C.A. M.THE ANALYST, 27 Method for the Quantitative Precipitation of the Casein of Human Milk. Engel. (Biochem. Zeits., 1908, 14, 234-237.)-The complete precipitation of casein from human milk by treatment with acids usually fails owing to the narrow limits within which the quantity of added acid must be kept. The author finds, however, that in the case of acetic acid the precipitation is not so dependent on the acidity of the mixture, and the following process is recommended: The milk is diluted with four times its volume of water (ic., 100 C.C. of milk are diluted to a volume of 500 c.c.), and for each I00 C.C. of milk taken 70 C.C. of TG acetic acid are added. The mixture is kept at a temperature of from 3" to 4" C. for about three hours, then shaken and heated for a, few minutes in a water-bath at a temperature of 40" C.The precipitated casein is finally collected on a filter. w. P. s. The Behaviour of Salol and Distearylsalicyl Glyceride in the Body. J. Bondzynski and V. Hunnieki. (Chew?,. Xeit., 1908, 32, 1117.)--The authors have devised a method for the quantitative estimation of salicylic acid in fwes and urine, and have thus been able to compare the behaviour of sdol and salicylic acid in the organism. They find that salol is eliminated from the system more slowly than sodium salicylate. The behaviour of distearylsalicyl glyceride was also studied in the same way. This glyceride, hitherto unknown, was prepared by the action of silver stearate upon dichlorhydrin salicylate. It melted between 46" and 49" C.C. A. M. Estimation of Urea in Urine. S. R. Benedict and F. Gephart. (Joul.1~ A?ncl-. Clzem, SOC., 1908,30,1760-1764.)--Folin's method, depending on the decompo- sition of urea, into ammonia on distillation with magnesium chloride, is difficult to control because the distillation must be carried almost to dryness, and yet not so far that hydrochloric acid is produced. The authors have devised an improved process which depends on the decomposition of the urea, in an autoclave in presence of hydrochloric acid. Five C.C. of urine, together with an equal volume of dilute hydrochloric acid (1 vol. of strong acid to 4 vols. of water), are introduced into a wide test-tube. The mouth of the tube is closed by a cap of lead-foil, and the tube is placed in an autoclave which is heated to 150" to 155" C., corresponding to a, pressure of about six atmospheres, this temperature being maintained for about an hour and a half. The contents of the tube are washed into a, distillation flask, diluted to about 400 c.c., treated with 20 C.C. of 10 per cent. sodium hydroxide solution, and distilled for about forty minutes into an excess oE standard acid. The residual acid is titrated, and the urea, is calculated after subtraction of the previously determined ammonia, nitrogen contents of the urine. The results are always slightly higher than those obtained by Folin's process, but they are probably more accurate. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9093400025

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

THE ANALYST, 27 ORGANIC ANALYSIS. Estimation of Vegetable Alkaloids by Means of Potassium-Mercuric Iodide. G. Heikel. (Chefla. Zeit., 1908, 32, 1149-1150 ; 1162-1163.)-The well- known Mayor’s reagent (6.775 grams of mercuric chloride and 25 grams of potassium28 THE ANALYST. iodide per litre) has been used for titrating alkaloid solutions, the reagent being added as long as a precipitate formed, but the composition of the prtcipitate is not constant, and depends on the concentration of the solutions. The author therefore proposes a modification of the method, and gives the amounts of the various alkaloids which are precipitated by a definite volume of the reagent. The details of the process are as follows : Ten C.C. of the alkaloid solution (containing 0.1 gram of the alkaloid) are treated with an excess of the reagent (not less than 15 C.C. excess should be added), and the mixture is diluted to a volume of 100 C.C. After filtering, 80 C.C.of the filtrate are treated with 10 C.C. of 10 per cent. ammonia, a definite volume (at least 10 c.c.) of 2; potassium cyanide solution is added, and the whole is then titrated with $G silver nitrate solution until a permanent turbidity is obtained. Working in this manner, the author has ascertained how many C.C. of the reagent are required to precipitate 0.1 gram of alkaloid, and under what conditions of dilution, etc., these results may be taken a6 being fairly constant. In most cases it was found best to perform the final titration in sulphuric acid solution. Aconitine (dilution 1 : 500) requires 6.2 C.C.of the reagent for each 0.1 gram of alkaloid; atropine (1 : 500), 10.8 C.C. ; berberine (1 : 500), about 10.7 C.C. ; brucine (1 : SOO), 7.9 c.c., but the volume of the reagent required increases with the dilution ; quinine- in neutral solution the amount of reagent required is fairly constant at 11.2 C.C. for any dilution between 1 : 500 and 1 : 1000; in acid solution (1 : 500), 19.8 C.C. are required; cinchonine (1 : 500), 11.0 C.C. in neutral solution and 19.9 C.C. in acid solution; cinchonidine (1 : 500), about 17.5 C.C. ; cocaine, about 12.2 C.C. ; and colchicine, 6.95 C.C. w. P. s. Formation of Formaldehyde in Cane-Sugar Solutions. A, A. Ramsay. (JOZLWZ. and PTOC. Roy. SOC. of New South Wales, 1907, 41, 172-1$5.)---Trillat has previously shown (see ANALYST, 1906, 31, 410) that formaldehyde is produced in traces when cane-sugar is heated to 125O C., and in greater quantity at 150" C.The author now states that formaldehyde is also formed in minute quantity when solutions of cane-sugar are heated at 100" to 103" C. Thus, when a strong solution (approximately 20 per cent. by weight) of cane-sugar in water was boiled and dis- tilled, the liquid obtained after twenty minutes' distillation gave a faint reaction for formaldehyde with Hehner's milk-sulphuric acid test, as also did the distillate obtained after another twenty minutes. The first 5 C.C. redistilled from each of these fractions gave a strong reaction for formaldehyde. The residue in the retort from the original distillation, on being made up to its original bulk with water and re- distilled, gave a distillate containing a smaller amount of formaldehyde than the previous fractions.The final residue in the retort was clear and colourless, boiled at 101.5O C., and gave a strong formaldehyde reaction. Methods for the detection and determination of formaldehyde in jams, etc., by distillation are therefore shown, in the light of these results, to be valueless, since formaldehyde is produced in the manufacture of jam, and the quantity present will be increased by distillation. On distilIing acidified solutions of four samples of pure jam specially prepared by the author, distillates were obtained in each case giving a strong reaction for formaldehyde, and it was found that after half the liquid fromTHE ANALYST, 29 the retort had distilled over, the next fractions distilled contained more formaldehyde than the first fractions.The author found from 1.3 to 14.0 parts of formaldehyde per 100,000 in various samples of jam examined (process adopted not stated). Perrier in 1906 reported the presence of 0-2 to 0.33 part of formaldehyde in 100,000 in cider, and smaller quantities in other foodstuffs. Furfuraldehyde has been shown by Forster to be formed under conditions similar to those above described, but this compound, which was not found by the author, gives with Hehner’s milk-sulphuric acid test a faint pink zone at the junction of the two liquids, the colour ultimately changing to dark green; this reaction cannot be mistaken for that given by formaldehyde.Hehner’s milk-sulphuric acid test for formaldehyde was found to be the most delicate, and when carried out by adding the milk to the solution immediately before pouring in the sulphuric acid, 1 part of formaldehyde in 10,000,000 gives a characteristic reaction in a few minutes. A. R. T. New Indieator, Highly Sensitive to Weak Bases. E. Rupp and R. Loose. (Ber. deut. Chem. Ges., 1908, 41, 3905-3908.) - An indicator, as highly sensitive towards weak bases as phenolphthalein is towards weak acids, has long been a desideratum, particularly for the titration of ammonia, and the alkaloids. The authors claim to have found such an indicator in p-dimethylamino-azobenzene-o- carboxylic acid, which they term ‘6 methyl red.” This indicator shows colorations very similar to those of methyl orange-viz., yellow in alkaline and neutral media and bluish-red in acid solutions, but the change is sharper then in the case of methyl orange, and the indicator can be used for titrations with centinormal liquids.Methyl red is prepared by dissolving 5 grams of o-aminobenzoic acid in about 100 C.C. of alcohol, and adding 20 C.C. of strong hydrochloric acid, keeping the liquid at a low temperature. The amino group is then diazotised by adding 2.5 grams of sodium nitrite dissolved in a small quantity of water, and the product is combined wiih 4.65 grams of freshly distilled commercial dimethylaniline, which is dissolved in 25 C.C. of alcohol, together with 5 C.C. of hydrochloric acid. The mixture is heated on the water-bath for half an hour, and then poured into water.The product is recrystallised from acetic acid. The indicator consists of a 0.2 per cent. alcoholic solution of the recrystallised product. J. F. B. Decomposition-Curves of some Nitroeelluloses of American Manu- facture. 0. Willeox. (Jouriz. Amer. Chem. SOC., 1908, 30, 186.)-Obermuller’s test (Mitteilung am dem Berliner Bezirksverein des Vereins deutscher ChemikeT, October 11, 1904) consists in heating the sample in an evacuated tube to a standard temperature, and observing at definite intervals the pressure of the gaseous decom- position products. The author modifies this method to the extent of distinguishing between tests in which the pressure, allowed to rise constantly, is observed at definite intervals, and tests in which the pressure is measured during intervals alternating with other intervals in which the gases are removed from contact with the sample by pumping them off.tests with increasing initial pressure ” and 6 6 tests with constant initial pressure ” respectiv’ely. The rate of These he calls30 THE ANALYST, increase of pressure varies with the volume of the apparatus, and their relation, for the '( test with constant initial pressure," is represented by PV= K. The curve for the average values of K represents nearly the course of decomposition of nitro- cellulose when heated in a vacuum. tests with constant initial pressures," and more particularly the curve for K, are made up of alternate approximately horizontal and rising portions, suggesting the appearance, as decom- position proceeds, of new phases or components which successively add their decomposition pressure or accelerative action to the characteristic decomposition pressure of the nitrocellulose, corresponding with the first approximately horizontal part of the curve.From SaposhnikoWs equations (Journ. Russ. Phys. Chem. SOC., 1906, 38, llSS), representing the relation of velocity of decomposition to temperature for the ranges 125" to 400" C., and 145" to 155" C., for each of which the ratio is expressed by a straight line, it follows that the temperature at which the ratio changes sharply, represented by the intersection of these lines, is 143" C. The author finds experi- mentally there are two such points-at 140" C. and 146" C. Curves representing 0. E. M. A New Reaction of Petroleum.E. Molinari and P. Fenaroli. (Ber. deut. Chem. Ges., 1908,41,3704-3707.)-When Russian petroleum is treated with ozonised air at 10" ozone strength at a temperature of 8" to 10" C., a white, flocculent preci- pitate forms after about an hour. This precipitate may be collected on a cold dry filter, and washed with light petroleum spirit, boiling-point below 40° C. I t consists of an ozonide of the unsaturated hydrocarbon constituent, C17H,, of the naphthene series, which occurs in Russian and Roumanian oils; its formula is C,,H,,O,. It may be kept for several days at a low temperature, but decomposes ir; a few minutes at 20" C. and very rapidly at 45" to 50° C., forming a soft red substance, which itself is converted at 105" C. into a brown resinous body.The ozonide is soluble in ether, chloroform, and benzene, but is precipitated by light petroleum spirit. The hydro- carbon which yields this ozonide is concentrated in the higher boiling fractions of the oil. Crude petroleum from Velleja in Italy yielded small quantitiee of an ozonide (C15H,60,J, a lower homologue of the same series. Thus the ozone reaction serves for the separation of the unsaturated hydrocarbons with ethylenic bonds from the other constituents of the oils, and to a certain extent assists the identification of the origin of given samples of petroleum. The separation of the unsaturated constituents produces no change in the optical rotation of the petroleum, and the optical activity cannot therefore be attributed to these hydrocarbons, neither is it due to the presence of cholesterol as such.J. F. B. The Analysis of Soap Stock. C. Stiepel. (Seqenfabrikant, 1908, 28, 42; Chem. Rev.'Fett- ZL. Harz-Ind., 1908,15, 289.)-Estimation of the fat in soap stock or concentrated soap stock by extraction with petroleum spirit usually yields an impure product containing mucilaginous and resinous substances. The author therefore recommends a preliminary treatment of 20 grams of the sample with hydrochloric acid, followed by extraction with 100 C.C. of petroleum spirit and evaporation of 50 C.C. of the extrad. I n the case of concentrated soap stock (which has already been treatedTHE ANALYST. 31 with acid in the course of manufacture) this preliminary treatment is unnecessary. The fat obtained from the extract is boiled for twenty minutes with 50 C.C.of alcohol and 5 grams of potassium hydroxide dissolved in a little water, and the soap solution diluted with 40 C.C. of water, and extracted with petroleum spirit. The resinous sub- stances (2 to 3 per cent.) will now be dissolved by the petroleum spirit. The residual soap solution is decomposed with acid, and again extracted with 100 C.C. petroleum spirit, which now dissolves the fatty acids, leaving the impurities that had been dissolved by the alkali, The fatty acids left on evaporation of 50 C.C. of the petroleum spirit extract are practically pure, though still of a dark colour. C. A. M. The Precipitation of Sugars by Means of Cupric Hydroxide. S. Yoshi- mito. (Zeitsch. physiol. Chem., 1908, 56, 425-445.)-1t was first shown by Salkowski that dextrose can be almost, if not entirely, precipitated if, to a solution containing this sugar and copper sulphate, sodium hydroxide be added.The precipitation is most complete when the substances are present in the proportion of 1 molecule of dextrose, 5 molecules or^ copper sulphate, and 11 molecules of sodium hydroxide. The author confirms this statement, the result of his investigation showing that all but traces of the dextrose were precipitated. Experiments were also carried out to ascertain to what extent other sugars are precipitated in this manner. The solutions contained amounts of the sugars equivalent to 4.5 per cent. of dextrose. It is seen from the results that only partial precipitation takes place, the maximum amount of sugar removed from solution being reached when the solution contained a certain amount of sodium hydroxide; this amount was different for each of the sugars examined.When the maximum was reached, the addition of more sodium hydroxide caused some of the precipitated sugar to redissolve. The following are the maximum quantities of sugar which can be precipitated : Laevulose, 89.4'7 per cent. ; galactose, 90.83 per cent. ; sucrose, 59-66 per cent. ; maltose, 61.58 per cent. ; lactose, 82.02 per cent. ; raflinose, 95.93 per cent, ; arabinose, 77.84 per cent. ; xylose, 92.07 per cent. The author does not consider the reaction to be of any use for the separation of the different sugars. w. P. s. The Nitrophenylhydrazones of the Sugars. A. Reclaire. (Ber. deut. Chem. Ges., 1908, 41, 3665-3671.)-The author has prepared the 0-, m-, and p-nitro- phenylhydrazones of several sugars ; this is best done in aqueous alcoholic solution, since in acetic acid solution osazones are too readily produced.The following table shows the melting-points of the various derivatives, those places which are left blank indicating cases in which crystalline hydrazones could not be obtained : Dextrose Mannose Lavulose Galactose Sorbose Ara bi nose Xylose Rharnhose Para. Meta. Ortho. ... ... 1.87"-188" C. 115°-116" C. 148" C. ... ... 194"-195" C. 162"-163" C. 173" C. ... ... 176" C. - 155'-156' C. ... ... 194" C. 181°-182" C. 172" C. ... ... 181"-182" C. 179"-180" C . 180" C. ... ... 185" C. 104°-105" C. 151" C. - - - ... ... ... ... 154'-155" C. (12Oo-13O0 C.) -32 THE ANALYST.It will be noted that the m- and o-nitrophenylhydrazones generally possess lower melting-points than the p-derivatives ; they are also more readily soluble. The p-nitrophenylhydrazones are generally more characteristic than the others. J. F. B. Analysis of Oil of Turpentine, and Estimation of Mineral Oil in Rosin Oil. R. Adan. (Bz~ll. SOC. Chim. Belg., 1908, 22, 389-396.)-Herzfeld's method of estimating mineral oil in oil of turpentine (ANALYST, 1904, 29, 222) or in rosin oil is shown to be unreliable, since pure rosin oils or turpentine oils containing such oils give large amounts of substances insoluble in fuming sulphuric acid (17 to 25 per cent.), whilst pure turpentine oils may give 1 to 2 per cent. of insoluble matter. The nitric acid method (ANALYST, 1903, 28, 42) gives much better results, especially if the test be made at a temperature of - 10" C.Under these conditions turpentine oils, which consist almost entirely of terpenes, are completely dissolved by the acid, whereas mineral oil remains undissolved. Certain rosin oils, however, which contain small quantities of naphthenes in addition to terpenes and sylvestrenes, may also yield an insoluble deposit (about 2 per cent.) in the test. In case of doubt, it is advisable to examine the products of the distillation of the sample between 128" and 150" C., and to determine their solubility in aniline and acetic anhydride. If the liquids are miscible in all proportions, mineral oil cannot be present in any notable quantity. C. A. U. Philippine Terpenes and Essential Oils.11. Ylang-Ylang Oil. R. F. Bacon. (Philippine Journ. Science, 1908, 3, 65-86.)-The production of ylang-ylang oil is an important industry in the Philippine Archipelago, The oil is prepared by the steam-distillation of the ripe yellow flowers of bnnangium odoratum, Baill. (Cananga odora$a, Hook), and has the following constants: Specific gravity at 30"/4" C., about 0.905 to 0,960, the finest oils having a high gravity; optical rotation at 30" C. in a 100 mm. tube, - 32" to - 45" for first-grade oils, and about (or exceeding) - 60" for inferior oils ; refractive index [n],, at 30" C., rarely exceeding 1.4900 for first-grade oils, and up to 1.5000 for second-grade oils, which latter contain considerable quantities of cadinene and resinous constituents.The value of the oil increases with the ester number, which reaches only to about 80 in the case of second-grade oils, while first-class oils have an ester number of 100 or more. A first-grade oil may give an acetyl figure of 74, a second-grade product of 42. Well-prepared oils have no acidity. Pure ylang-ylang oil leaves, after distillation in vucm, 5 per cent. of non- volatile residue having a refractive index at 30" C. of 1-5400 ; while if 5 per cent. of cocoanut oil be present in the oil, the refractive index of this residue is 1.5000. Distillation of the pure oil at 10 mm. pressure gives over 50 per cent. of distillate below 100" C. in the case of first-grade oils. Ylang-ylang oil has been found by the author to contain formic acid (as ester) and iso-safrol, in addition to its previously known constituents, which include the following : Acetic (?), valeric, benzoic, and salicylic acids (as esters) ; methyl and benzyl alcohols ; pinene, cadinene, and other terpenes and sesquiterpenes ; linalol, geraniol, eugenol, iso-eugenol, and para- cresol (probably as methyl esters) ; creosol [the methyl-ether of homopyrocatechin,THE ANALYST.33 CoH3(CH,)l.(OCE3)3.(OH)4] ; and probably inethyl anthranilate, to which the fluorescence of the oil is due. Though very little adulteration of this oil appears to be practised in the Philippines, it is said to suffer adulteration by admixture with alcohol, turpentine oil, cocoanut and other fixed oils, and kerosene, all of which may be detected by the usual methods.Ylang-ylang oil of good quality dissolves in 2 volumes of 75 per cent. (volume) alcohol, with faint opalescence ; but second-grade oils are not com- pletely soluble in alcohol of this strength, although they are dissolved by 90 per cent. alcohol, in which most fatty oils are only soluble with difficulty. The odour of ylang-ylang oil still remains the most important criterion of quality. A. R. T. Characteristics of Montan Wax. J. Marcusson. (Chem. Rev. Fett- ZG. Harz- Ind., 1908, 15, 193-195. j-Montan wax is obtained by extracting peat with petroleum spirit or benzene, and is purified by distillation with superheated steam. The purified product, which is used for candles, is not yet commercially important, but the crude wax is largely employed as an insulating material.A sample of the latter examined by Ubbelohde's method became fluid at 83.5" C., and had a dropping-point of 84.3" C. It consisted, in the main, of compounds of high molecular weight with alcohols of high melting-point, and j ts complete saponification was difficult. It was eventually effected by dissolving 10 grams of the wax in 50 C.C. of benzene, and heating the solution for eight hours on the hot-water bath with an excess of alcoholic potassium hydroxide solution. The crude montanic acid separated from the saponified liquid was a solid brown substance with a neutralisation value of 143. By treatment with hot petroleum spirit it could be decomposed into dark insoluble hydroxy acids melting above 100" C., and a light, soluble, wax-like substance melting below 100" C.These acids did not give Liebermann's cholesterol reaction. The wax contained only traces of volatile acids. The unsaponifiable matter was a dark brown wax-like body, which gave the cholesterol reaction on treatment with acetic anhydride and sulphuric acid. When recrystallised from alcohol and decolorised with animal charcoal this substance yielded a yellow wax-like body, which no longer gave the cholesterol reaction, whereas the residue left on evaporation of the alcoholic solution gave a pronounced coloration in the test. The wax had a strong optical rotation, and preliminary experiments, to determine to which constituents this was due, showed that the unsaponifiable matter and the acids soluble in petroleum spirit were dextrorotatory. Montan wax is regarded by Kramer and Spilker as the parent substance of petroleum, and the author's experiments may thus throw light upon the origin of the optically active constituents of petroleum. C. A. M. Estimation of Water in Fats, Oils, and Fatty Acids. C. Stiepel. (Seijen- sieder Zeit., 1908, 886; through Chem. Zeit. Rep., 1908, 32, 626.)-The fat in which the water is to be estimated is placed in a flask through which a current of dry carbon dioxide is passed. The flask and its contents are heated by means of a small hot-air oven to a temperature of 105"-110" C., and the gas issuing from the flask is passed through an absorption vessel. The volatile fatty acids collecting in this vessel are34 THE ANALYST, titrated at the end of the drying operation, and their amount is subtracted from the total loss undergone by the fat in the flask, in order to ascertain the real loss due to the evaporated water . w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9093400027

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

34 THE ANALYST, INORGANIC ANALYSIS. Separation of the Alkali Metals Electrolytically. J. S. Goldbaum and E. F. Smith. (Journ. Amer. Chem. Soc., 1908, 30, 1705-1711.)-1n a previous paper (ANALYST, 1907, 32, 428) the authors showed that the halide salts of the alkali and alkaline earth metals could be readily determined quantitatively with the help of a mercury cathode and rotating silver anode. In the present paper, results obtained with ammonium chloride are described. In order to avoid losses owing to the decomposition of the ammonium amalgam and solution of the silver chloride from the anode by the ammonia formed, it was found necessary to remove the amalgam as fast as it was produced. This was accomplished by bringing the electrodes nearer together (1 cm. distance) and increasing the speed of rotation to 750 revolutions per minute.A slight excess of standard acid was introduced into the outer cup, and the ammonia, estimated by titration. In the estimation of czesium and rubidium by this method, the slightest impurity in the salt will cause the decomposition of the amalgam in the inner compartment, with formation of brown silver oxide on the anode. For the analysis of lithium chloride this electrolytic method is better than any other gravimetric process. The separation of the various alkali metals by the electrolytic method waB effected in the Hildebrand cell by taking advantage of the different electrical decomposition pressures of their salts. When the pressure is below the decomposition point, the pressure can be gradually increased without a corresponding increase in amperage.When the decomposition pressure is reached, any increase in pressure meets with a proportionate increase in current density. Thus the curve expressing the current density in relation to the pressure shows a sharp “break point,” corresponding to the decomposition of the salt in question. This point being determined for the various pure salts under any given set of conditions, the analytical separation of two metals in the Hildebrand cell is merely a matter of maintaining the voltage at a suitable point between the decomposition pressures of the two salts. Satisfactory results have been obtained with all the metals of this group with the exception of mixtures of salts of potassium and ammonium, the decomposition values of which lie too closely together.J. I?. B. Determination of Boric Acid in Insoluble Silicates. E. T. Wherry and W. H. Chapin. (Journ. Anze~. Chem. SOC., 1908, 30, 1687-1701.)-The authors describe two separate methods which they have employed for the estimation of boric acid in complex mineral silicates : Volumetric nl!ethod.-Unless the distillation method (see below) be employed, great difficulty is experienced in effecting the complete separation of the boric acid from the alumina ; the authors have obtained a fairly satisfactory solution of thisTHE ANALYST. 35 difficulty by effecting the precipitation of the alumina by calcium carbonate, which does not combine with boric acid, The procedure is as follows: The sample is fused with about 3 grams of sodium carbonate for fifteen minutes.The melt is dissolved in 20-30 C.C. of dilute hydrochloric acid and a few drops of nitric acid to oxidise ferrous iron. The solution is placed in a flask and heated nearly to boiling, dry calcium carbonate is added in moderate excess, and the whole is boiled for ten minutes under a reflux condenser, since boric acid is volatile with steam. The precipitate is filtered and washed on a small Buchner filter, the total volume being kept below 100 C.C. To eliminate all carbon dioxide, the filtrate is returned to the flask, a pinch of calcium carbonate is added, the liquid is again heated to boiling, and connected with a filter-pump through a splash trap ; suption is continued until boiling ceases. If the precipitate shows a red colour due to iron, it is filtered again, phenolphthalein is added, the liquid is made alkaline with & sodium hydroxide, then 1 gram of mannitol is added, and more sodium hydroxide, until a pink colour, which is permanent in presence of another gram of mannitol, is obtained.Distillation Method-The apparatus consists of a distillation flask in which the vapours of methyl alcohol are generated; this is connected with a reaction flask containing the acid solution of boric acid solidified by means of about an equal weight of dry calcium chloride. The vapours of methyl alcohol are distilled into the decomposition flask, which is heated, and the methyl borate produced is carried through a condenser into a, receiver closed by a water trap; two or three of these receivers are at hand, and the distillate is collected in fractions of 100 C.C.As each fraction is obtained, paranitrophenol indicator is added, and the free mineral acid is neutralised; the liquid is then made alkaline to phenolphthalein, and double the amount of alkali required for this operation is added in excess. The alcohol is then distilled off and the residue made up to 25 C.C. The colour of both indicators is next carefully discharged by the addition of acid, and the liquid is heated under reduced pressure to expel carbon dioxide. The final titration is made in presence of glycerol or mannitol in the usual way, the difference between the end-points of the two indicators being a measure of the boric acid. J. F. B. Studies on Capillarity and Absorption and a Method for the Estimation of Mineral Aeids in very Dilute Solution.1. Holmgreen. (Biochem. Zeits., 1908, 14, 181-208.)-Aqueous solutions containing less than 1 per cent. of hydro- chloric acid are not absorbed equally by paper ; the water spreads more rapidly than the acid when the flow is horizontal or vertical, and, as a result of this phenomenon, paper filters a portion of the acid from the water. The weaker the acid solution, the more apparent is the action. If small spherical drops of dilute hydrochloric acid be placed on an absorbent paper (stained with Congo-red), the strength of the acid may be ascertained by measuring the rate at which the acid and water diffuse over the paper. The percentage proportions of acid and water to one another are obtained from the distances to which the acid and aqueous ‘‘ rings ” travel.If a strip of the paper be dipped partially in a dilute solution of hydrochloric acid, the same phenomenon is observed, and the difference between the capillary flow if the acid36 THE ANALYST. and water is constant for any definite concentration of acid. Dilute solutions of nitric, sulphuric, and phosphoric acids, and sodium hydroxide, behave in a similar way to hydrochloric acid. w. P. s. Gasometric Estimations on the V. Meyer Vapour-Density Principle. J. Mai. (Ber. dezit. Chem. Ges., 1908, 41, 3897-3904.)-1~ a previous paper (ibid., 1902, 35, 4229) the author described a method for the gasometric analysis of carbonates, oxalates, sulphites, etc., making use of a V. Meyer vapour-density apparatus for the evolution of the gas at a high temperature. The apparatus, as now improved, is shown in the accompanying figure.The heating jacket, a, contains a liquid boiling at a suitable temperature-e g., water, toluene, xylene, or aniline ; d is a thermo-regulator, el is a reflux condenser, and e2 a tube for the admission of steam if that medium be used. The V. Meyer bulb, f, con- tains concentrated sulphuric .*l acid; it is connected with the gas burette by a hori- zontal tube, h, 1 metre long and 4 mm. wide. The sub- stance to be analysed is weighed out in a small glass tube 27 to 35 min. long and I 6 mm. wide. This tube has a few small holes 4 to 6 mm. below its top edge, so that the acid may p e n e t r a t e readily ; t h e s u b s t a n c e should be covered with a layer of sodium sulphate to moderate the initial evolu- tion of the gas.This tube is held at the point hi either by a Mahlmann's stopcock or by a stout rubber joint pinched by a screw-clip until the air in the bulb has been heated to a constant temperature, and the level of the mercury in the burette has been read. The glass tube is then caused to fall into the acid, and fifteen minutes are allowed for complete decon~position. The mercury levels are then accurately adjusted, and the stopcock i is closed. The burette is disconnected, and allowed to remain for a further fifteen minutes before the volume and temperature of the gas are read. With not more than 2 C.C. of strong sulphuric acid in the bulb, the absorption of carbon dioxide by the acid is negligible only at temperatures above 140" C.At lower temperatures and with larger quantities of acid, the error may be eliminated by previously saturating the acid with the gas at the temperature of the reaction by passing a current of carbon dioxide during the process of heating up. With large quantities of acid, several estimations may be made in succession without dismounting theTHE ANALYST 37 apparatus. The method gives exact results with carbonates of the alkalies and alkaline earths, with the exception of magnesium carbonate, since the magnesium sulphate is incompletely soluble in the strong acid. The carbonates of most other metals also show low results. J. F. B. Use of the Mercury Trough in Gas Analysis. A. Stock. (Ber. dezit. Chem. Ges., 1908, 41, 3834-3849.)-This form of mercury trough, the use of which was instituted in France by Berthelot, renders the most valuable service in all kinds of manipulations with gases.It is constructed of a solid block of stone, preferably marble, 35 em. high and 55 by 40 cm. in horizontal dimensions, The inside is not simply hollowed out like that of an ordinary pneu- matic trough, but contains, besides a large oval central cavity with a sloping bottom, a number of tubular borings of various depths and diame- ters. The tops of all these openings are covered by a layer of mercury about 3 cm. in depth. The whole trough contains about 160 kilos of the metal, and is supported on a stout wooden table mounted on rollers. At one side a, groove is cut in the top of the wall of the trough, and a piece of stout glass is inserted so that tubes may be brought up to the edge and the level of the mercury read off through the glass.For this purpose there is a boring 3.5 cm. in diameter and 23 cni. deep immediately in €ront of the glass into which the tube may be depressed. Amongst the manifold uses to which the mercury trough may be put are the collection and transference of gases and the bottling off of gases for storage, for which purpose stoppered bottles are used provided with a cup around the upper part of the stopper, the cup containing mercury as a seal. All the operations necessary in gas analysis are readily carried out in the mercury trough with simple apparatus, and the results can be obtained with a degree of accuracy not possible with any other form of apparatus.Owing to the great variety of the operations which may be performed with it, the mercury trough is particularly suitable for research work with gases. J. F. B. The Detection of Hydrogen Peroxide, Formaldehyde, and Persulphates. S. Rothenfusser. (Zeds. Unterszich. Nahr. Genzissm., 1908,16, 589-591.)-Hydrogen peroxide may be detected by shaking the solution containing it with a little milk- serum and about 10 drops of an alcoholic solution of benzidine ( c j . ANALYST, 1908,38 THE ANALYST. 33, 401) ; a blue coloration is produced if hydrogen peroxide be present. The milk- serum is prepared by precipitating milk with lead acetate, filtering, and adding 20 C.C. of 30 per cent. acetic acid to every 180 C.C. of the filtrate. The test is capable of detecting 1 part of hydrogen peroxide in 6,000,000.Very dilute solutions of persulphates (1 : 1,000,000) give a blue coloration with the above-mentioned benzidine solution. Formaldehyde may be detected by treating its solution with a reagent prepared by adding an ammoniacal silver nitrate solution to 10 C.C. of 16 per cent. potassium hydroxide solution ; the silver solution is prepared by treating a 2 per cent. silver nitrate solution with ammonia until the precipitate at first produced is redissolved. The silver solution is added drop by drop to the potassium hydroxide solution until a slight permanent precipitate is produced, and a drop of ammonia is then added to give a clear solution. Formaldehyde may be distinguished from formic acid by means of this reagent, as formic acid does not give a reduction at the ordinary temperature.Formaldehyde may be detected in milk by heating the latter with twice its volume of hydrochloric acid containing a trace of a molybdenum, uranium, cobalt, nickel, gold, platinum, silver, mercury, or copper salt; a violet coloration is produced. w. P. s. Volumetric Estimation of Mercury by the Thiocyanate, Iodometric, and Acidimetric Methods. E. Rupp. (Clzem. Zeit., 1908, 32, 1077-1079.)-Titration of mercuric salts with thiocyanate solution, carried out as in the case of silver salts, is applicable only if chlorides, mercurous salts, and nitrous acid are absent. The iodide method (ANALYST, 1907, 32, 128) can be used for mercuric nitrate, chloride, or sulphate. Mercurous salts, if present, are converted to the mercuric state by treatment with bromine water, the excess of bromine water being removed by gentle heating.Mercuric salts can also be titrated in neutral solution by means of potassium cyanide, standardised against standard acid solution, using methyl orange as indicator, or against pure mercuric chloride. Phenolphthalein may be used in this titration to indicate when all the mercuric salt has been converted to mercuric cyanide; more exact results are obtained, however, if an excess of the potassium cyanide is added and the solution titrated back with standard acid, using methyl orange as indicator. If the mercuric solution is acid, a considerable quantity of an alkali chloride is added to prevent hydrolysis of the mercury salt, and the solution then exactly neutralised with dilute sodium hydroxide solution and phenolphthalein, after which the titration is carried out in either of the two ways given above.Mercuric cyanide itself is titrated by treating it, in dilute solution, with an excess of potassium iodide, and then titrating the potassium cyanide formed with standard acid, using methyl orange as indicator. Mercuric oxide is estimated by shaking it for five to fifteen minutes with a fairly strong solution of potassium iodide, and titrating the potassium hydroxide formed. A. G. L. New Method for Estimating Mercury Vapour in Air. P. Menikre. (Compt. Eend., 1908, 146, 754; through BUZZ. SOC. Chim., 1908, 3, 1104.)-Traces of iiiercury vapour present in air are absorbed by leading the air through boilingTHE ANALYSTY 39 nitric acid (specific gravity 1.383).The solution obtained is freed from excess of acid, and mercury estimated colorimetrically by means of diphenylcarbazide, which is capable of detecting 1 part in 4,000,000. If the quantity of mercury present is greater than 1 part in 10,000, it may be titrated with sodium iodide. A. G. L. Estimation of Potassium as Potassium Phospho-Molybdate. A. Schlicht. (Chem. Zeit., 1908, 32, 1125-1126, 1138-1140.) - The rtuthor severely criticises Raulih’s phospho-molybdate method for the estimation of potassium (Compt. Rend., 1890, 110, 289) as tedious and inaccurate. He communicates some preliminary results, which show that it is possible to estimate accurately potassium sulphate by evaporating it to dryness with a solution of sodiuin molybdate and phosphoric acid in nitric acid, to which magnesium sulphate is added, treating the residue with warm water, filtering the precipitate on asbestos, washing first with a solution of magnesium bulphate, next with a solution of ammonium nitrate, then with alcohol, and finally with ether, and drying or igniting the precipitate; the weight obtained, divided by 8.071 in the first case, or 7.860 in the second, gives the weight of potassium sulphate present. The author proposes to extend his investigations. A. G. L. Molten Hydrated Salts as Solvents for the Freezing-point Method. G. Cock. (Zeits. Anoqj. Chenz., 1908, 60, 191-192.)-The author has recalculated some results obtained by J. Livingstone, R. Morgan, and H. K. Benson (ANALYST, 1907, 32, 396) for the molecular weight of water dissolved in molten hydrated salts, and shows that the results vary from 155 to 241, instead of from 17 to 24, as stated. He himself has obtained similar results, and concludes that such salts are not suitable solvents for use in the freezing-point method. A. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9093400034

出版商:RSC    

年代:1909

数据来源: RSC

摘要:

THE ANALYSTY 39 APPARATUS, ETC. Simultaneous Estimation of Carbon, Hydrogen, Nitrogen, etc., in Organic Compounds by the Simplified Method of Combustion Analysis. M. Dennstedt and F. Hassler. (Ber. dezit. Chem. Ges., 1908, 41, 2778-2782.)- Dennstedt’s simplified method of combustion analysis (ANALYST, 1897, 22, 277 ; 1905, 30, 135 and 348; 1907, 32, 434; 1908, 33, 112) has now been developed to permit of the simultaneous estimation of the nitrogen and other elements, as well as the carbon and hydrogen. The oxygen employed must be free from both carbon dioxide and nitrogen. I t is generated in a separate tube by heating potassium permanganate. The elimination of nitrogen from the apparatus is best effected by displacement, a strong current of oxygen being passed through the apparatus for one to one and a half hours.In order to have the supply of oxygen under complete control, a capillary T-piece is inserted immediately after the generating tube, one branch being connected with a weighted rubber gas-bag. The combustion and absorption apparatus is constructed in the usual way, with an arrangement for dividing the stream of oxygen. Between the last absorption U-tube and the palladium chloride bottle a back-pressure valve is inserted, to40 THE ANALYST. prevent the liquid from being sucked back. The oxygen is absorbed by a hydro- chloric acid solution of cuprous chloride, maintained in the reduced condition by a roll of copper gauze. This is contained in an Erlenmeyer flask, through the stopper of which passes a T-piece for the gas connections and a tube, reaching to the bottom, which is connected with the pressure reservoir.Before the combustion is begun, the gas-bag should be partially filled with pure oxygen. The elimination of the air is then effected by alternately filling and partly emptying the bag by producing alternately a strong or feeble evolution of oxygen from the permanganate, all the gas being passed through the apparatus. After the combustion, the passage of oxygen is continued for twenty minutes, and the nitrogen is collected in the cuprous chloride flask. After standing all night it is free from oxygen, and is transferred to a Hempel burette. In order to estimate the nitrogen retained in the form of nitrate by the lead peroxide, the latter is extracted with 33 per cent, alcohol and the salt is weighed, the calculated nitrogen being added to the gas measurement. The lead peroxide also contains the sulphur, which is estimated in the ordinary way.In the case of substances containing halogens, the usual silver boat is inserted in front of the lead peroxide. ?T. F. B. Apparatus for Evaporating from Basins in a Vacuum. E. Donath. (Chm. Zeit., 1908, 32, llO7.)-The apparatus here shown in section consists of the two parts a and b made of copper, and clamped together by means of six clamps (d), with a ring of asbestos pulp ( I ) covered with a ring of asbestos paper placed between the edges. I n the upper portion there are openings into which are fitted tubes (t, t ) , one of which is con- nected by means of the india- rubber tubing ( k ) with an air- pump, and the other with the vessel (20) containing the liquid to be evaporated. The central opening in the upper part is closed by means of a thick transparent glass plate, screwed down by clamps (s, s) upon an asbestos ring ( k ) , 60 as to form an air-tight conn ection.The basin (21) rests on a thin layer of asbestos in the cavity a. The flame beneath should be so regulated that the liquid does not boil, and the evaporated liquid should be condensed in a flask between the outlet and the air- PU*P* C. A. If.THE ANALYST. 41 Arrangement for Preventing Frothing in Crude Fibre Determinations. A. P. Sy. (Joz~m. Amcr. Chem. SOC., 1908, 30, 1792-1793.)-1n the estimation of crude fibre the substances are boiled for thirty minutes each time under a reflux condenser, with dilute solutions of acid and alkali.In the latter operation nearly all materials tend to froth very badly. The author describes an arrangement for preventing frothing, consisting of a series of digestion flasks and reflux condensers arranged side by side. The top of each condenser is connected by a tube with the digestion flask next in the series, and this tube passes down to within a short distance of the boiling liquid. The first digestion flask of the series is provided with a tube not connected with a condenser, and the last condenser of the series is con- nected with a suction pump. When the contents of the flasks are boiling, a current of cold air is aspirated through the apparatus, and striking down against the surface of the boiling liquid in each flask, effectually destroys the froth.J. F. B. Material for the Generation of Oxygen in a Kipp's Apparatus. L. Wolter. (Chmz. Zeit., 1908, 32, 1066.)-The decomposition of alkali peroxides by means of water or dilute acids is too violent for safety, whilst the addition of an inert organic substance such as paraffin has the drawback that the material some- times spontaneously ignites. On the other hand, the required conditions of slow decomposition and stability may be obtained by mixing the alkali peroxide with magnesium oxide, and incorporating the mixture with an inert fused salt, such as potassium nitrate. The most suitable proportions were found to be 25 grams of magnesium oxide and 100 grams of sodium peroxide, added little by little with constant stirring to 100 grams of potassium nitrate in a state of fusion in a large iron basin.The hard mass which is formed on cooling is broken up, and kept in a leaden box. Or decomposition may be prevented by coating the surface of the larger fragments with melted paraffin. When required for use these fragments are broken up, and decomposed in the Kipp's apparatus with dilute hydrochloric acid. The gas evolved is conducted through a solution of caustic alkali to remove the small amount of carbon dioxide it contains. C. A. M. Apparatus for Polarising at 87" C. A. P. Sy. (Joum. Amer. Chem. SOC., 1908, 30, 1790-1791.)--In polarising solutions of invert sugar in the jacketed tube at a temperature of 87" C., the author employs one of the commercial forms of rapid continuous water-heaters for heating the current of water passing through the jacket.These heaters are provided with valves for the separate regulation of the gas and water supplies, and the temperature of the hot water may be maintained remarkably constant. The polariscope tube should be joined to the water-heating apparatus by a flexible connection, so that the solution in the tube may be agitated. J. F. B.42 THE ANALYST. An Apparatus for Observing the Rate of Absorption of Oxygen by Polluted Waters, etc. W. E. Adeney. (PYOC. Boy. Dublin SOC., 1908, 11, 280-287.)-The author has shown in previous communications that the quantity of oxygen absorbed and the products formed during the two stages of aerobic fermenta- ! B b tions are constant if the same volumes of a polluted water be used and the amount of dissolved oxygen exceed that of the fermenting substances.For the determination of the rate and extent of such absorption of oxygen from the air the simple apparatus shown in the figure is recommended. I t consists of two flat shallow bottles, A and B, of similar capacity, closed with corks previously soaked in melted paraffin. Through one of these passes a capillary tube, GL, widening, above the cork, into a graduated tube, which is enlarged to a bulb at cil, and then bent downwards and continued until it passes through the cork of the other bottle at b. A second tube, provided with a stopcock, ri2 aud O,, is also passed through the cork of each bottle. In making an estimation the bottle 13 is partially filled with a known quantity of the polluted water, to which has been added a little magnesium hydroxide to retain carbon dioxide, whilst the same volume of distilled water is introduced into the bottle A.The stopcocks b, and b, are opened, the stopcock CL, closed, and the two corks inserted into their respective bottles. The apparatus is next immersed for a short time in a water- bath at the temperature of the room, after which a. note is taken of the temperature and barometrical pressure. The water, which will have risen through the capillary tube into the graduated portion, is then brought to the level of the zero point of the scale by cautiously opening the tap a2, and the stopcocks b, and b, closed. The pressure in A will then be that of the atmosphere plus that of the column of water in the capillary tube a, less the height due to Capillary action.The apparatus is kept at a temperature of 15" to 18" C., and shaken from time to time, or con- tinuously by mechanical ineans if the water is heavily polluted. As the oxygen is absorbed in 13 the pressure is reduced in A, and on opening the tap b, there will be a proportionate rise of water, which may be measured upon the scale. The volume of oxygen absorbed during the given period may be calculated by ineans of the equation-THE ANALYST. 43 Vt = 2v + 2’ --v -$(V - v), P where v’ represents the volume of oxygen absorbed at the initial temperature and pressure ; V the initial volume of air in A and B ; v, the volume of water that rises above the zero of the scale aa; p’, height of water in the capillary tube above the level it assumes by capillary action ; p”, height of water in the graduated tube above the zero-point ; 29 =p’ +p” ; and P, the pressure of air in B at the beginning in terms of the water barometer.The initial pressure in A will be P +p’. For controlling the purity of waterways and the like, the bottles should hold about 1,200 C.C. and a litre of the water be used. Under the least favourable conditions the allowable absorp- tion at 15’ to 18” C. should be about 5.5 C.C. per litre in forty-eight hours, whilst for tidal waters it may amount to 3.5 C.C. per litre in six and a quarter hours, or 4.0 C.C. per litre in twelve and a, half hours. The graduated portion of the tube should con- tain about 3 C.C. and be graduated in & c.c., whilst the bulb a, should have a capacity of about 1 C.C.For testing unpurified sewage bottles of a capacity of 1.500 C.C. are used, and the graduated tube should contain 10 C.C. and give readings of & c.c., whilst the capacity of the bulb should be 10 C.C. Such samples must be diluted with five to ten times their volume of pure water ; or the oxygen may be replenished by the addition of a measured quantity of that gas from a nitrometer connected with the apparatus. When only small quantities of water are available the bottles A and B may have a capacity of 120 to 150 c.c., and the graduated tube a capacity of 0.3 C.C. and give readings to i+B c.c., whilst the bulb a, should contain 1 to 2 c.c., the latter being necessary when it is required-e.g., to determine the quality of an effluent from a filter-bed, C.A. M. SODA-WATER. REPORT OF THE MEDICAL OFFICER O F HEALTH, CITY OF LONDON, 1908. Of three dozen samples of soda-water collected from various shops in the City, no less than nineteen were found to be unstltisfactory when submitted to a bacterio- logical examination, In every case where the water was found to be unsatisfactory some sufficient cause was found and pointed out to the manu€acturers, who at once expressed their intention of taking active steps to remove the source of contamination. Arrangements have also been made to register the names of those manufacturers who have agreed to carry out certain regulations proposed by the Medical Officer of Health as to the sanitary conditions of their factories, analysis of water-supplies, and examination of finished products.So far forty firms have been registered, and it is proposed to keep up the standard by systematic inspection. w. P. s.44 THE ANALYST. NEW BOOK. A TEXT-BOOK OF INORGANIC CHEMISTRY. By Dr. A. F. HOLLEMAN. Issued in Third English Edition ; partly ~ v o . , viii + 502 pp., including index and 81 figures ; cloth, $2.50. The present edition represents a revision of the work by both the Dutch author and the American editor. The portions on the phase rule, spectroscopy, radio- activity, iron-carbon system, and metal ammonia compounds, have been largely re-written by the author, and the chapter on colloids, experimental determination of equivalent weights, and unity of matter is new. English in co-operation with H. C. COOPER. re-written. New York : John Wiley and Sons. London : Chapman and Hall, Ltd. INSTITUTE OF CHEMISTRY. THE following candidates passed the Final Examination for the Associateship in the Branch of Biological Chemistry, held from October 19 to 23 : E. B. Anderson, B.Sc. (London and Birmingham); F. G. S. Baker, M.A. (Oxon); EL L. Gammon, and A. R. Smith, B.Sc. (Manchester). The following Associate also presented himself for the Examination, and was awarded the Certificate : J. H. Totton, B.A., B.Sc. (R.U.I.). The Examiner in Biological Chemistry was Dr. Arthur Harden, F.I.C., and the Examiners in General Chemistry were Mr. Bertram Blount, F.I.C., and Professor Herbert Jackson, F.I.C.

ISSN:0003-2654    

DOI:10.1039/AN9093400039

出版商:RSC    

年代:1909

数据来源: RSC