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1. |
Note on the examination of liniment of camphor |
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Analyst,
Volume 23,
Issue November,
1898,
Page 281-282
Norman Leonard,
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THE ANALYST. NOVEMBER, 1898. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS, NOTE ON THE EXAMINATION OF LINIMENT OF CAMPHOR. B Y NORMAN LEONARD, B.SC., F.I.C., AND H. METCALFE SMITH, F.I.C. LINIMENT of Camphor has long been commonly known as Camphorated Oil," but this synonym has only been made official in the British Phamzacopcx?ia of 1898. The latter, as also the editions of 1867 and 1885, directs 1 ounce of camphor to be dissolved in 4 fluid ounces of olive oil, but no characters or tests for the finished preparation are given. Taking the specific gravity of olive oil as 0.9165, this being the mean of the limits (0.914-0-919) allowed for this oil by the Phurmacopaia, it is easy to calculate that the liniment should contain 21.45 per cent. by weight of camphor. We have recently met with several specimens which were deficient in camphor, one sample containing only 3 per cent.of this substance, and in two cases a mineral oil was found to have been substituted for olive oil. The amount of camphor present is most simply and accurately found by deter- mining the loss in weight experienced by the sample on heating. For this purpose 3 to 5 grammes of the camphorated oil are heated for two hours at 120" C. in a flat- bottomed dish or flask. Olive oil under the same conditions suffers EL gain in weight of 0.15 per cent., and hence this figure should be added to the loss in weight on heating the sample, in order to obtain the true amount of camphor present. The results obtained by this method are very satisfactory, as will be seen from the follow- ing table, in which are given analyses of four solutions prepared by dissolving known weights of camphor in olive oil of 0.9164 specific gravity :- Camphor Olive Oil Camphor LO35 on Corrected Loss Specific Gravity Grammes.Grammes. per Cent. per Cent. per Cent. (H,O a t SO"=l). taken, taken, calculated, Heating, =Camphor, a t 60" F. 1 ,.. 2.361 75.918 3.01 2.93 3-08 0.9178 2 ... 5.346 70.578 7.04 6.78 6-93 0.9195 3 ... 14.530 69.912 17.21 17.10 17-25 0.9241 4 ... 15.856 54.146 22.65 22.38 22 -53 0.9266 An approximation to the amount of camphor may be made by determining the specific grsvityof the sample, each per cent. of camphor, as may be seen from the results given above, raising the specific gravity by about 0.00045. The following formula mag be used, it being remembered that the results obtained will be of little282 THE ANALYST, value if oil having a specific gravity much differing from 0.9165 has been used in the preparation of the sample :- specific gravity of sample -09165 0.00045 Camphor per cent.= Below are given the figures obtained from four specimens of “Liniment of Camphor,” No. 1 being prepared by ourselves, and the remaining three procured from chemists and druggists. As already observed, the directions given by the Pharma- cop~%a correspond to the presence of 21.45 per cent. of camphor : Specific Gravity Camphor from Loss on Camphor calculated at 60“. Heating (corrected). f rom Specific Gravity. 1 ... 0.9264 21.35 22.2 2 ... 0.9255 20-65 20.0 3 ... 0.9257 20-46 20.4 4 ... 0-9264 20.37 22.2 As regards the presence of mineral oil, this is usually indicated by the marked biuish fluorescence of the sample. It may be further identified, and separated from any vegetable oil which may also be present, by heating for some time with alcoholic potash, the liquid being afterward8 diluted with water and filtered. The mineral oil remaining on the filter is washed with water, dried, and transferred to a weighed flask by means of a little ether, which is subsequently removed by evaporation. We are indebted to Dr. Thomas Stevenson for permission to make use of results obtained in his laboratory.
ISSN:0003-2654
DOI:10.1039/AN8982300281
出版商:RSC
年代:1898
数据来源: RSC
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2. |
The relation between the specific gravity and the insoluble fatty acids of butter and other fats |
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Analyst,
Volume 23,
Issue November,
1898,
Page 282-283
Norman Leonard,
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摘要:
282 THE ANALYST, THE RELATION BETWEEN THE SPECIFIC GRAVITY AND THE INSOLUBLE FATTY ACIDS OF BUTTER AND OTHER FATS. BY NORMAN LEONAHD, B.Sc., F.I.C. THE existence of a general correspondence between the specific gravity and the percentage of insoluble fatty acids yielded by butter and margarine is well known, a low specific gravity being, as a rule, associated with a high percentage of insoluble fatty acids, and vice vers&. Occasionally, abnormal results are obtained, more especially the conjunction of a high percentage of fatty acids with a comparatively high gravity. It is obvious that no natural or necessary connection exists between the two analytical data, since the fats used to adulterate butter vary in character, and the rough correspondence actually observed is due to the fact that the usual adulterants (beef and mutton fat, etc.) have approximately equal densities and yield the same proportion of insoluble fatty acids.The presence of a vegetable oil, such as cotton-seed, cocoanut, or sesamd oil, having a higher density than animal fats, but yielding nearly the same proportion of fatty acids, would be indicated by a departure from the usual relation. The investigation of the latter may, therefore, be of some value to the analyst. Four years ago I found, on examination of the analyses of thirty-three samples of butter, that the results might be very well represented by the formula y = k(1- x)% where y is the percentage of insoluble fatty acids, x the specific gravity at 100" F.THE ANALYST. 283 (water at 60" F.=I), and k: a constant, the mean value of which was found to be 951fl.6. I have recently examined the results obtained from thirty samples analysed during the year 1897, and found k to have the mean value 951fl.8. This close agreement with the previous result is interesting as showing the constancy of the general character of the adulterants employed. The following table is calculated from the formula y = 951(1 Specific Gravity at 100" F. (H,O at 60" F. = 1). -8990 -8995 *9000 -9005 -9010 -9015 -9020 *go25 -- x) : Insoluble Fatty Acids. 96-1 95.6 95.1 94.6 94.1 93.7 93.2 92.7 Specific Gravity at 100" F. (H,O at 60" F. = 1). Insoluble Fatty Acids. -9040 91.3 -9045 90.8 -9050 90.3 -9055 89.9 -9060 89.4 -9065 88.9 -9070 88 04 -9075 88.0 -9080 87.5 i -9085 87.0 *go30 98.2 9035 91.8 Of the sixty-three samples examined, the percentage of insoluble fatty acids found by experiment differed from that calculated from the formula, By not more than 0.5 per cent. in thirty-five cases, or 56 per cent. By not more than 1.0 per cent. in fifty-four cases, or 86 per cent. There were only three cases in which a difference of more than 1.4 per cent. was The results discussed above were obtained in the laboratory of Dr. Thomas observed, and in each of these the insoluble fatty acids were abnormally high. Stevenson, to whom I am indebted for permission to make use of them.
ISSN:0003-2654
DOI:10.1039/AN8982300282
出版商:RSC
年代:1898
数据来源: RSC
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3. |
Foods and drugs analysis |
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Analyst,
Volume 23,
Issue November,
1898,
Page 283-284
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THE ANALYST. 283 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. A. Bomer. (Zeit. der UH tersucla. der Nahr. mad Genussmittel, 1898, 544.)-In two previous papers (Zeit. fiir Uiztersuch. der Nalw. und Genussmittel, 1898, 21, Analyst, xxiii., 42 ; Zeit. fiir Untcrsuch. dey ,Valw. z~1zd Geiazisssnittcl, 1898, 81, Analyst, xxiii., 132) the author published a method for the extraction of phytosterin and cholesterin, and showed that the phytosterin of vegetable fats, particularly that of cotton-seed oil, possesses sufficient characteristic differences from the cholesterin of animal fats to enable small quantities of the former to be detected in the presence of the latter. He now applies this principle to the detection of cotton-seed oil in lard. The proof of the presence of phytosterin in cholesterin rests upon the melting- point and the crystalline structure of each body.The crystalline structure is, however, of itself sufficient evidence, should the quantity of phytosterin be too small t o decidedly affect the melting-point of the mixture. The crystals of such mixtures Detection of Cotton-Seed Oil in Lard by Means of Phytosterin.284 THE ANALYST. consist of short, apparently rounded needles, in part attached to one another in telescope fashion. Experiments made by slow crystallization upon larger quantities, however, yielded crystals in the form of three-sided prisms with flat ends. The results of the author’s study of the melting-points of the two bodies have already been publiahed (cf. Analyst, xxiii., 132).He now gives the results of a large number of observations of the melting-points and crystalline form of various mixtures of lard and cotton-seed-oil, which show that admixtures of 3 to 4 per cent., and, under favourable conditions, even 1 to 2 per cent., of cotton-seed oil in lard can be detected in this way. The author claims that this mode of detection is easier and quicker of execution than the determination of the iodine number of the liquid fatty acids, H. H. B. S. Estimation of Glycogen in Meat Extracts. Lebbin. (Phamz. Zeit., 1898, xliii., 519 ; through Chem. Zeit. Rep., 1898,214.)--Twenty-five grammes of the sample are dissolved in 100 C.C. of water, mixed with 100 or 150 C.C. of a 4 per cent. solution of caustic potash in 90 per cent. alcohol, and allowed to rest for one or two hours. The precipitate is filtered off, washed with 90 per cent. spirit, dissolved off the paper with 50 C.C. of water, and the solution faintly acidified with weak hydrochloric acid. It is next precipitated with about 10 C.C. of a solution of potassium mercuric iodide, filtered after half an hour, and the insoluble matter washed with hot water. From the filtrate the glycogen is thrown down on the addition of an equal volume of 95 per cent. alcohol, collected on a tared filter, washed with alcohol and ether, dried and weighed. The double mercuric iodide is prepared by dissolving 20 grammes of mercuric chloride in 300 C.C. of water, mixing with 20 grammes of potassium iodide also dissolved in 100 c.c., and adding more mercuric chloride as long as the precipitate continues to disappear. F. H. L.
ISSN:0003-2654
DOI:10.1039/AN8982300283
出版商:RSC
年代:1898
数据来源: RSC
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4. |
Organic analysis |
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Analyst,
Volume 23,
Issue November,
1898,
Page 284-300
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284 THE ANALYST. ORGANIC ANALYSIS. The Characteristics of Olive-Kernel Oil. 0. Elein. (&it. mzgezu. Chem., 1898 847-850.)-According to Benedikt and other authorities this oil differs froin olive oil in having a sharp and bitter taste and a dark green colour and in being readily soluble in glacial acetic acid and alcohol on account of the large percentage of free acids which it contains. The author finds that this curious difference between the oils extracted from different parts of the same fruit is largely to be attributed to the manner in which the oil is obtained. After crushing the fruit so as to leave the stones intact the mass is subjected to more or less complete expression in bags of esparto grass. The residual mass (bagasses) is left aside for a considerable time often weeks and is subsequently ground again and expressed or extracted.Under these circumstances, it is not surprising that considerable oxidation takes place in the moist mass and that the oil frequently contains as much as 50 to 60 per cent. of free fatty acid and is of a dark colour from the oxidation OE the chlorophyll of the fruit. A specimen of ‘‘ kernel ” oil thus obtained gave the following results on analysis THE ANALYST. 285 Specific gravity 0.9277 ; iodine value 71.57 ; saponification value 190.5 ; free fatty acid 71-12 per cent. The author prepared specimens of the pure kernel oil by hot and cold expression, and obtained the following analytical results with them Specific gravity 0.9186 to 0.9191 ; iodine value 8699 to 87.78 ; saponification value 182.3 to 183.8 ; free acids, 1.00 to 1.78; refractive index 1.4682 to 1.4688.From these results it appears that the specific gravity and iodine value of pure olive-kernel oil are somewhat higher than is usually the case with alive oil. Only in exceptional instances and with oil obtained from such varieties as Seville Cordova, and Manzanilla olives is so high an iodine value given by olive oil. The saponi-fication value is rather lower and the percentage of free acid higher than in olive oil. The percentage of free acids in the oil obtained from sound fresh fruit varied from 0.4 to 0.8 per cent. and the author attributed the difference to oxidation during the time which elapsed between the removal of the endocarp and expression of the oil. In order to determine whether the presence of kernel oil in olive oil caused any depreciation in the latter experimental mixtures were prepared in 1891 and 1892, and preserved in well-stoppered bottles in the dark until 1898.The samples showed scarcely any change in colour taste or smell and the amount of free acids had only increased by about 0.2 per cent. The author examined a specimen of olive-kernel oil by Hazura’s method and found it to contain 9.7 per cent. of solid fatty acids (consisting of 40 per cent. of stearic acid and 60 per cent. of palmitic acid). The liquid fatty acids were found to consist of oleic and linolic acids. Arachidic acid was not detected in the solid fatty acids. The general conclusions arrived at from the research were : 1. The characteristics hitherto assigned to olive-kernel oil are really those of 2.The physical and chemical characters of pure olive-kernel oil are very similar 3. Olive-kernel oil is as stable as olive oil if proper precautions are taken. 4. It can be mixed with olive oil without ill effects and there is no reason why Oagasses oil. to those of olive oil. the stone and the fruit should not be crushed and pressed together. C. A. M. Separation of Unsaturated from Saturated Fatty Acids. K. Farnsteiner. ( Z e i t . fiir Untersuch. clev. Nahy. m i l Geiaussrdtel 1898 390.)-The author’s method is founded upon the fact that warm benzene dissolves the lead salts of the solid as well as the liquid fatty acids but that on cooling the salts of the solid fatty acids crystallize out almost completely leaving the salts of the liquid fatty acids in solution.0.6 to 1 gramme of fat is saponified with alcoholic alkali in an Erlenmeyer flask the solution neutralized with acetic acid using phenolphthalein as indicator the alcohol almost completely expelled by evaporation the soap dissolved in about 100 C.C. of boiling water and precipitated with about 30 C.C. of a boiling solution of lead acetate containing about 1 gramme of the salt. By agitating the flask in cold water in the usual way most of the lead salts are separated from the fluid in a compact mass 286 THE ANALYST. After complete cooling the filtrate is removed by decantation through a moistened filter leaving the bulk of the lead salts in the flask. This as well as the small quantity on the filter is then washed with cold water after which that upon the filter is washed back into the flask.The flask is now placed upon a bath of boiling water when in a short time the lead salts will be found to melt together into a, compact mass. By agitating the flask as it cools any remaining crystals of the lend salts can be made to adhere to the sides of the flask and the liquid can then be poured off clear. The salts are now as far as possible dried by means of a roll of filter-paper and are then dissolved in 50 C.C. of moderately warm benzene The solution is allowed to stand for about fifteen minutes at the temperature of the laboratory in order to obtain a coarse crystalline separation and is then kept for two hours at 8" to 12" C. The filtration is conducted in the following manner The flask is closed by a tight-fitting cork through which two glass tubes pass one a straight piece about 10 cm.long reaching about 1 cm. into the flask and the other bent in the form of a syphon. Into the open end of the bent tube inside the flask is fixed a moderately thick wad of cotton-wool free from fat extending a few millimetres outside the orifice. By compress-ing the air within the flask by means of the ball the liquid is forced through the plug of cotton-wool up the bent tube and can be collected in a flask placed to receive it. When the liquid has been thus removed the cork is lifted and about 10 C.C. of benzene, at a temperature of about 10" C. is run into the flask. This is agitated with the precipitate and then removed by compressing the caoutchouc ball as before.Twenty-five C.C. of benzene are then added the bent tube lifted out of the liquid the benzene heated to boiling to dissolve the precipitate then cooled for one hour at 8" to 12" C. and removed by filtration through the plug as before. This operation is repeated yet again with 25 C.C. of benzene altogether from 120 to 130 C.C. of benzene filtrate and washings being obtained. For the separation of the liquid fatty acids the filtrates are shaken in the usual way with an equal volume of 10 per cent. hydrochloric acid until the salts are completely decomposed and after two washes with water the solution of the fatty acids is filtered through wadding and distilled in a current of hydrogen. For the separation of the solid fatty acids 25 to 30 C.C.of benzene are added to the lead salts in the flask the bent tube lifted above the level of the fluid and the benzene heated for a short time to the boiling-point. The flask is then removed from the water-bath and the pressure-tube closed with the finger causing air to enter through the cotton-wool plug owing to the condensation of the benzene vapour. Most of the liquid in the tube and plug is thus sucked back into the flask. The plug is then withdrawn and thoroughly extracted by boiling in a test-tube several times with a few C.C. of benzene Finally the lead-salts are decomposed by heating the benzene solution for fifteen minutes with a 10 per cent. hydrochloric acid solution and the same treatment pursued as in the case of the liquid fatty acids except that the use of hydrogen in the distillation of the benzene is omitted.I n the case of the separation of free fatty acids the author converts them into the lead salts by means of hydrated lead oxide prepared by precipitating lead acetate The short vertical tube is connected with a caoutchouc ball THE ANALYST. 287 with sodium hydrate washing with water alcohol and ether drying at a gentle heat, and reducing to a fine powder. For 1 part by weight of the solid fatty acids about 0-4 part of the hydrated lead oxide are required and for 1 part of the liquid fatty acids about 0.2 part. An excess of the hydrated lead oxide is without influence upon the results. The following results show the degree of accuracy obtainable : ~ X O . ~ 1. 2. 3. 4. 5. 6.7. 8. 9. 10. ~ Quantity in Grammes taken for the Analysis. 0.7260 0.6646 0.9155 0.9104 0.6456 0.6190 0,4960 0.6333 0.5799 0.7834 C.C. of 3enzene used. 120 120 100 150 100 90 100 125 110 90 4 4 4 3 3 3 3 3 3 2 Liquid Acids. Taken, per cent. 19.1 21-35 33.75 44.0 47.1 51-2 56.8 59.5 60.6 91.0 Found, per cent. 17.45 22-4 30.8 42.5 45.05 48 -8 55.8 -61-0 89.4 Solid Acids, Taken, per cent. 80.9 78.65 66.25 56.0 52.9 48.8 43.2 40.5 39.4 9-0 Found, per cent. 82.4 77.5 67-9 -54 -7 48 *7 43.3 39 -4 39.4 10.8 Remarks. Old oleic acid. Ditto. Ditto first filtrate allowed to stand overnight. Ditto.Liquid acid from olive oil. Ditto first filtrate allowed to stand overnight. Old oleic acid. Liquid acid from cotton oil. Freshly prepared, almost pure oleic acid. The author then developes the following argument that the percentage of unsaturated fatty acids in a mixture of fatty acids or in a fat can also be ascer-tained by calculation from the iodine number of the mixture and the iodine number of the liquid portion of the fatty acids without it being necessary as stated by Twitchell (ANALYST 1895,165) to determine approximately the quantity of the latter. Let J be the iodine number of the substance and J the iodine number of the liquid portion of the fatty acids. Then since J parts by weight of iodine correspond to 100 parts by weight of 100 the liquid fatty acids it follows that 1 part by weight of iodine corresponds to parts by weight of the liquid fatty acids.The quantity of iodine (J) absorbed by 100 parts by weight of substance consequently corresponds to looJ parts by weight of the liquid fatty acids. The formula '?oJ therefore gives the percentage of liquid fatty acids in the substance, The iodine number of a sample of lard for example is 54 and the iodine Jl Jl J 288 THE ANALYST. number of the liquid portion of the fatty acids is 90. The sample will contain 10\i24 - . = 60 per cent of liquid-i.e. unsaturated fatty acids. The accuracy of this method is influenced first by the accurate determination of the two iodine nunibers ; secondly by the amount of loss in iodine-absorbing power suffered by the unsaturated fatty acids through oxidation etc.during their prepara-tion; and thirdly by the question as to whether in the case of the incomplete separation of the lead salts the unsaturated acids remaining in the insoluble lead salts are sufficient to influence the iodine number of the principal quantity. H. H. B. S. Use of Benzene in the Determination of the Iodine Numbers of Fats and of the Liquid Portion of Fatty Acids. ( Z e i t . fiir Untersuch. der Nahr. und Ge?a.z6ssmittel 1898 529.)-In a recently published paper ( Z e i t . fiir Unter-such. der ATah? m d Genussmittel 1898 390 diacclgst preceding Abstract) the author proposes a method for the separation of unsaturated from saturated fatty acids by meam of benzene. I n the present communication he shows that the iodine nunibers of fats and of liquid fatty acids may be determined in the presence of benzene if the latter be free from thiophen.Ordinary benzene owing to the presence of this impurity absorbs an appreciable quantity of iodine and therefore vitiates the results, I(. Farnsteiner. The following comparative results were obtained : Description of Fat. 1. Lard I. repared by author . 2. 3. Cooking fat (fabricated) 4. Tallow I. . . . . 5. , II. Australian . . 6. , III. 9 . * * 7. Goose-fat I. pure . . . 8. , II. ) . . . 9. , III. with lard admixture , 10. Sesame oil . . . . 11. Cotton-seed oil . . . 12. Linseed oil . . ._ . . . , II. P rom local slaughter-house . . . . . Iodine Number found in Presence of / -u Ckloroform.49.0 497 76.1 40.2 44.3 44.7 69.8 77.7 72.9 103.9 Benzene.' 48.7 49.5 75.2 39.7 44.0 44.1 69.0 77.9 72.2 103.1 101.1 100.8 178.9 I 177-0 Difference by use of Benzene. - 0.3 - 0.2 - 0.9 - 0.5 - 0.3 - 0.6 - 0.8 + 0.2 - 0.7 - 0.8 - 0.3 - 1.9 For the determination of the iodine number of the liquid fatty acids the author takes a portion of the mixed fatty acids corresponding to about 1 gramme of the liquid fatty acids-that is to say about 2 grammes for lards etc. and about 1.2 to 1.5 grammes for oils. The lead salts are produced in the usual way and then dissoIved in 100 C.C. of warm benzene the solution allowed to stand for 10 to 15 minutes kept for 2 hours at 8" to 12" C. and filtered without subsequent washing.The liquid fatty acids are obtained in the free state by shaking the filtrate with about 100 C.C. of a 10 per cent. hydrochloric acid solution until the layer of benzene become THE ANALYST. 289 nearly clear. After washing twice with 100 C.C. of water the benzene solution is filtered through paper or cotton-wool without washing. From the filtrate three 25 C.C. portions are taken; two of these are used for the determination of the iodine number in the usual way ; the third is used to ascertain the weight of the fatty acids taken for the determination by distilling off the benzene in a current of hydrogen. The iodine number can also be determined in the residue from the distillation. I n the following table the results by the benzene method are compared with the results by the ether method.The two experiments in which benzene only was used are intended to show that the absorptive power of the fatty acids is not affected by the distillation in hydrogen. N O . ~ I. 11. 111. IV. Description of Fat. Lard prepared by author Ditto . . . . Lard American Cooking - f a t , composed of tallow a n d cotton oil Mean . M i x t u r e o f fatty acids Mean . Iodine Number of the Liquid Portion of the F a t t y Acids. Sepuation effected by means of Ether. & 1. 90.7 -1234 L 12 133-1 13 c Benzene. v -. 1. ~ 86.5 -96.2 124 *5 132.7 2. 86.5 -96.2 124.5 132.7 After Distilling off Ren-zene. 3. 86-5 93.0 96.3 125.3 131.6 Remarks.Solution of the lead salts stood over-night with-out hydrogen. S e p a r a t i o n by e t h e r carried out under heat. Without hydrogen. Lead salts produced by boiling the benzol solu-tion of the fatty acid with hydrated lead oxide. By ether ; over-night, under hydrogen. By benzene ; three hours exposed to air after precipitation. Lead salts stood over-night under hydrogen. H. H. B. S. The Separation of Bi-basic Fatty Acids resulting from the Oxidation of Fats. L. Bouveault. (Bull. SOC. chim. 1598 xix. 562-565.)-1n the course of experiments on adipic acid the author had occasion to separate the various fatty acids in a mixture derived from the oxidation of a fat and consisting principally of succinie adipic glutaric and pimelic acids.The following is an outline of the method which he adopted : By distilling the mixture under ordinary pressure until the temperature reache 290 THE ANALYST. 230" C. the whole of the succinic acid was converted into succinic anhydride which could then be separated from the other acids by continuing the distillations under a pressure of 20 mm. when it passed over at 135" C. The residual mixture of bibasic acids (boiling at 210" to 225" C. under 20 mm. pressure) was treated with cold ether which dissolved about one-third of the total quantity, The insoluble portion (M.P. 135" to 140" C.) consisted chiefly of pimelic and adipic acids and deposited the latter on crystallization from boiling water. The adipic acid thus obtained melted at 140" C.and though insoluble in water was found to be extremely deliquescent. The glutaric and pimelic acids dissolved in the ether and in the mother-liquid of the aqueous crystallization were separated by being converted into calcium salts and treated with water in which calcium pimelate is but slightly soluble in the cold and insoluble on boiling whilst calcium glutarate is exceedingly soluble. The author states that Arppes' statement that pimelic acid is not present in products of the oxidation of fats with nitric acid is incorrect; in fact in such oxidations he has found all the usual acids present in varying quantity from succinic up to sebacic acid. The Fractional Saponification of Oils and Fats-11. R. Henriques. (Zcit. angew. Chem. 1898 697-702.)-This paper contains some supplementary notes to the author's former communication on this subject (ANALYST this volume 181-183).It is stated that the conclusions arrived at as to the formation of ethyl esters of the fatty acids with liberation of the glycerin during the saponification of tri-glycerides with alcoholic potash were forestalled by Bouisin in 1857 who drew the same deductions from a similar serieg of experiments (Comptes Rend. xlv. 35 ; J. pralc. Chenz. 185'7, lii. 308). Recently Geitel ( J . prak. Cliem. 1897 429 ; 1898 113) has come to the conclu-sion from mathematical and physical considerations that in the saponification of all partially decomposed tri-glycerides mono- and di-glycerides are produced. Without attempting to refute this view on theoretical grounds the author points out that Geitel has brought forward no experimental evidence in favour of his theory with the exception of certain results which in his (the author's) opinion lend more support to the theory of the production of ethyl esters.Moreover since in his former paper the author suggested the possibility of di-glycerides being present in the residue left on saponifying linseed oil with a smaller amount of alcoholic potash than was requisite to liberate all the glycerin he has made further experiments on this point with almond oil and finds that only unaltered tri-glycerides are left. Even on treating almond oil for eight hours with steam at 250" to 270" C. so as to cause a disruption of the molecule and distillation of about 10 per cent. of the substance the residual portion when washed from liberated fatty acids and glycerin was found to contain only unaltered tri-glycerides.C. A. M C. A. M. The Determination of the Lubricating Power of Oils. E. Weiss. (Dingier's Polyt. JOZLWL. 1898 cccix. 76-S0.j-The viscosity of an oil is often regarded as th THE ANALYST. 291 most important factor in determining the suitability of an oil for lubricating purposes, but in the author’s opinion it should not be regarded as the sole criterion. By means of an apparatus which he has devised it is possible to determine the consis-tency of an oil and from the result to calculate the “mobility ” (Beweglichkeit) which furnishes a means of judging which of two oils with the same viscosity is the better lubricator. This apparatus consists essentially of a small metal disc about 10 cm.in diameter which is made to revolve in the oil by means of clockwork actuated by a weight the number of revolutions in a given time being dependent on the consis-tency of the oil The weight is chosen so that the disc makes 150 revolutions in water at 15” C. in half a minute. On charging the vessel with a thick liquid and varying the driving weight the resistance of the liquid is proportional to the rapidity with which the disc revolves or P = mu where P = the driving force u = the number of revolutions in thirty seconds, and m=a constant of the oil under examination. I n the case of rape oil this constant was found to he 64.27. For more mobile liquids it was determined experi-mentally that up to a weight of 2,500 grammes the following formula was applicable, P = a + b g in which a = 43.5 and b = 0.60853.For liquids whose consistency lies between that of water and rape oil the relation between the driving weight and rapidity of revolution is more complex ; but here too the author demonstrates that there is such a constant relation and arrives at the formula P=Apvo (I-a) in which A is a constant depending on the dimensions of the consistency apparatus 2ro = the rapidity of revolution of the oil near the disc p = the coefficient of friction of the liquid and a denotes what fraction the rapidity of revolution near the surface is of the rapidity of revolution near the disc. For Engler’s viscosimeter which the author employs the law of Poiseuille holds good T= Bp in which T= the time of efflux of the liquid and B = a constant of the particular apparatus used.Incorporating this formula into his previous equation the author arrives a t Usually about 1,147 grammes are required. the formula, If then in the examination of a number of oils the same viscosimeter and consistency apparatus and in the latter the same driving weight are invariably used, PB A has always the same value and the product of the number of revolutions and of the time of efflux in the viscosimeter must be proportional to the constant which varies with the value of u. Thus a and Tvo furnish a measure of the 1 1 -a’ mobility of a fluid since the more mobile a liquid the less the difference between the rapidity of its revolution in different parts of the vessel.Hence the product Tv is termed by the author the ‘( mobilit,y.” I f the ‘( mobility ” were solely dependent on the coefficient of internal friction, all liquids with the same viscosity would have the same ‘ I mobility,” which is not the case. The (‘ mobility ” steadily decreases as the temperature rises and when the consistency exceeds thirty revolutions fatty oils lose their oily character 292 THE ANALYST. Vis-:osity. I n the case of rape oil the relation between the consistency value ( U ) and the viscosity value ( V ) can be expressed with approximate accuracy by the formula and this formula was used to calculate the figures in the fourth row of the sub-joined table which gives the comparative results obtained with that oil at varying temperatures : No.of revolutions 17 20 24 28 30 36 40 50 56 Minutes (viscosi-meter) . . 21 17.3 14-2 12.0 11.15 9.0 7.9 5.8 4.5 TVo . . 357 346.0 340.8 336.0 334-5 324.0 316.0 290.0 252.0 Minutes (calcu-(V+ 1.92) ( U - 0.08) = 387.54 ; lated) . . 20-98 17-53 14.28 11-96 11.03 8-87 7.78 5.84 5.01 The curves of the changes in the viscosity and consistency caused by dilution The following tables give in an abridged form some of the determinations made are parallel to the curves of those brought about by heat. by the author in illustration of the foregoing points : I. Temp. Rape Oil and Colophony 10 1. -Vis-cosity. Glycerin, Specific Gravity 1.233 at 20" C. r 7 Temp* Rape Oil. /--Liquid Paraftin. Revolu-tions in Consis-tency Apparatus Minutes Vis-cosity.-I 19.0 14.65 10.8 10.0 6.6 4.15 2.45 M O -bility. Vis-cosity. Mo-bility. Vis-cosity. Mo -bility. Vis-cosity. MO-bility. remp. Temp. Temp. Temp c. --17.4 21.4 26.0 27.0 34-0 43.4 54.0 c. ---9.0 16.2 18.2 25-6 35.4 45.0 = C. 10.6 13.3 15.6 19-8 24.6 25.8 30.9 37.7 40.8 31-2 26-5 22.5 16.7 12.3 11.4 8.4 6-0 5.2 312-0 318.0 315.0 300.6 295.2 296.4 302.4 288.0 27 0 -4 10 . 12 . 14 . 18 . 24 . 26 . 36 48 . . . 56 . --266.0 263.7 259 -2 260.0 237.6 199-2 137-2 ---19.7 14.2 13.0 9.0 6.2 4.50 - --354.6 340.8 338.0 324.0 297.6 252.0 ----3244 334-1 313-2 288.0 -Castor Oil.Mineral Oil I. Mineral Oil 11. - I Liver Oil. /-I Revolu-tions in Oonsis-tency Apparatus, 10 . 12 . 14 . 18 . 24 . 26 . 36 . 48 56 . Culinutes, Vis-cosity. Mo-bility. Vis -:osity. Mo-bili t y . Mo -bilit . &lo-bility. Temp. Femp, c. --26.6 30.3 34.8 36.0 42.8 50.4 -O c. " c. - O c. -c -51.3 57.0 58.4 -------297.6 299-0 280.8 264.0 224.0 --20.6 15.6 12.1 11.2 7-6 5.0 ---288.4 280.8 290.4 291.2 273-8 260.0 -I --319.2 317.6 314-4 312.0 ----22.8 17.7 13.1 12.0 -51.2 56-2 62.3 64.2 -7.9 9.5 17.7 27.5 37. THE ANALYST. 293 11. Melted lard at 41.2" .. , 43.8" . . , 47.2" . (4 . . . ( b ) (4 (4 (74 (4 9 , 9 . Lubricating soap dissolved in water spirit at dilferent temperatures : . . . . . . Aqueous solution of gum arabic : . . . . . . . . . . . . Soluble glass . . and . . . . . . . No. of Revolutil ns in Consistency Apparatus. 52 54 56 22.1 24.1 61.4 13.65 31% 59.6 35.5 V iscosiineter Minntes. 4.8 4.35 3.9 . . . 12.8 10-15 . 2.5 - 19.9 8.6 6.4 5-6 . . ' 3 Mobility. 249.6 2349 218.4 282.9 244-6 153-5 291.6 273 5 453.4 198.8 A comparison of these results shows that as regards ( ( mobility " the substances in the tables stand in the following ascending order Soluble glass glycerin soap solutions gum solutions oils.The latter compared with one another have the following classification Rape oil rape oil with colophony melted lard mineral oil II., liquid paraan castor oil liver oil mineral oil I. A characteristic property of castor oil is that its ( I mobility " increases as it becomes more fluid. C. A M. Some Properties of Pure and Adulterated Wax. K. Dieterich. (Chcm. Zeit., 1898 xxii. 729.)-The author finds that the iodine number of pure yellow beeswax, as determined by the ordinary Hubl process varies between 8.8 and 10-7 ; employing the Waller method the figures are 8-4 and 10.5 respectively. As the absorption is small it is better to use 0.5 or 0.75 gramme for analysis dissolving it in 40 C.C. of chloroform and allowing the mixture to rest overnight before adding the iodine solution.Yellow wax whether filtered or not is completely soluble in chloroform ; but white wax is not entirely dissolved. The iodine number of white wax is 4.2 to 4.4 (Hubl) 4.0 to 4.2 (Waller). A wax-like residue obtained in the manufacture of wool-grease has recently appeared on the market ; and as it is much cheaper than beeswax it may possibly be used as an adulterant. Its iodine number is 7-8 to 14.2 (Hiibl) 3.1 to 3.7 (Waller) ; chloroform does not dissolve it wholly. A genuine sample of yellow wax was mixed with 10 and also 20 per cent. of various foreign substances of similar nature (cf. table) the final iodine number of the product being determined in each case Most of the bodies selected for trial affect the absorption one way or the other ; but Carnauba and Japan wax make practically no difference.The former however forms a mixture which is only partly soluble in chloroform ; while beeswax sophisticated with Japan wax is entirely soluble. The addition of ceresin or paraffin also causes imperfect solubility. On the whole it would seem that the iodine absorption of true wax is subject to such wide variations that by itself it cannot always be relied upon to indicate the presence of impurity; that the degree of solubility in chloroform is a most important factor ; and that t 294 THE ANALYST. ensure even reasonable accuracy in the valuation of any particular sample it is necessary also to deduce the acid ester and saponification numbers of the material. The annexed table shows the general result produced on the constants of genuine wax by the several adulterants quoted : Specific dcid Ester Saponification Iodine Gravity.No. PU’O. No. No. Paraffin . . Stearic acid . Ceresin . . Carnauba wax . Japan wax . Lard . . Beef tallow . Colophony . raised raised raised raised - lowered raised lowered raised -lowered -lowered -raised raised raised raised lowered raised raised lowered lowered lowered -- - unchanged raised raised unchanged raised raised raised raised raised raised lowered raised raised F. H. L. Extraction of Cholesterin and Phytosterin. H. Kreis and 0. Wolf. (Chem. Zeit. 1898 xxii. 805.)-Although the process described by Bomer (ANALYST xxiii. 42) affords most valuable information as to the derivation of a fat it is lengthy com-plicated and in hot weather unpleasant owing to the large volumes of ether consumed.If only 10 grammes of the sample are taken for analysis as Bijmer has more recently suggested the product is almost too small for proper examination ; and Raumer’s idea of evaporating the soap solution and extracting the dry residue with ether is not so easy to carry out as it sounds. The authors hope that the following modification will prove more simple and acceptable 50 grammes of fat are saponified with alcoholic caustic soda. The solution is evaporated in a porcelain basin till it becomes syrupy poured into 500 C.C. of boiling water in a 2-litre flask and mixed with hydrochloric acid (sp. gr. 1.124) until phenolphthalein shows that the liquid is only just alkaline.100 C.C. of a 10 per cent. aqueous solution of calcium chloride are then added and the whole is shaken till the lime soaps cohere into lumps. (Absence of frothing shows that sufficient of the reagent has been employed.) I t is next cooled to the ordinary temperature filtered through cloth and the precipitate squeezed dry in paper. Thus prepared the soaps form a friable mass and contain the whole of the cholesterin and phytosterin. The product is powdered boiled for an hour with 100 C.C. of 95 per cent. alcohol cooled and filtered. The filtrate is treated with 3 C.C. of 40 per cent. soda to attack any saponifiable matter left behind on the first occasion and evaporated slowly to dryness. The residue is broken up and shaken for an hour with 50 C.C.of ether filtered and evaporated once more. This final product is readily soluble in hot spirit; and on cooling the cholesterin and phytosterin separate out pure and white. Bomer has remarked (ANALYST xxiii. 132) that the cholesterin of butter is difficult to obtain pure; the present process is available in this case also. Hitherto it has been tested on butter lard and cotton oil; details will follow in a subsequent communication. F. H. L. Reaction of Lecithin with Alloxan. N. Orlow. (Fawmx. J. 1898 xx. 283 ; through Chem. Zeit. Rep. 1898 233.)-If alcoholic solutions of lecithin and alloxa THE ANALYST. 295 (which must be free from nitric acid) are mixed together the liquid turns pink red, and dark a voluminous red precipitate being formed. The reaction proceeds almost instantaneously on warming.The precipitate is readily soluble in water decomposing on evaporation even in the desiccator into a brown powder resembling murexide. Ammonia does not affect the colour. The aqueous solution of the precipitate yields a violet or blue deposit with lead acetate and ammonia. Cholesterin and fats give the reaction only on heating and in a far less marked degree. Pure cholesterin does not change in colour more quickly than the alcoholic solution of alloxan alone. F. H. L. The Tornoe Spectro-areometric Method for Estimating Alcohol and Dry Extract in Beer. M. Buisson. (Rev. Chim. Analyt. AppZ. vol. vi. [lo] pp. 157-164.) -The apparatus (Fig. 1) consists of a special refractometer fitted with a graduated circle and vernier for reading off the refraction in degrees minutes and seconds, and employing a Hallwachs’ prism (A) illuminated by a monochromatic (sodium) FIG.1. flame (K). The prism consists of a rectangular vessel divided by a partition into two compartments one of which is filled with distilled water and the other with the beer under examination previously freed from carbon dioxide. Equalization of temperature in the contents of the prism is ensured by agitating the whole before each reading. Of the light thrown on the prism (Fig. 2) in the direction of the partition the rays falling on the partition are deflected by the latter and refracted through the beer their course being indicated by M N 0 P R whilst the other rays follow the direction M’ N’ 0‘ P’ R‘ the field to the right of M N being thus illuminated, whilst that to the left of the partition remains dark.The line of demarcation (M N Fig. 3) is well defined and its direction can be accurately determined by the aid of the cross wires in the apparatus 296 THE ANALYST. In working the apparatus the pristn is first carefully cleaned filled and put in position on the stand the base of the eye-tube B (Fig. 1) being placed in contact with the tip of the adjusting screw E which Frc;. 2. m n is then turned until the zero of the vernier coincides with the 180" mark on the scale. The eye-tube is then trained on to the lamp-flame, and the prism adjusted so that the partition is in line with the mark I on the condenser L the part filled with water being on the left hand. The eye-piece is focussed on the cross wires, and the eye-tube-still in contact with the screw &-is turned so as to bring its extremity opposite to the compartment containing the beer the scale also being rotated at the same time.This procedure brings into the field of vision the line of demarcation If N (Fig. 3), the ill-defined section at the extreme right being if necessary placed out of view by simply turning the scale and attached apparatus in the proper direction. The platform carrying the prism is rotated so as to bring the line M N in line with the intersection of the cross wires, whereupon the position of the prism in relation to the 180" mark on the scale is noted. The prism is then rotated B O O and the position of the line J!t N-now to the left of the central partition-is ascertained as before the angle of deviation indicated by the position of the zero mark of the vernier being then read off and referred ti0 the table which gives the correspond- -FIG.3. ing quantity of dry extract. The standard temperature for the operation being fixed at 17-5" C. the following corrections must be made for other tempera-tures viz. for deviations of 15O 20" and 30" an addition of 0.7 1.0 and 1.2 respec-tively for each degree C. above 17.5" C. and a corresponding deduction in cases where the temperature is below that standard as determined at the moment of reading off by a thermometer inserted in the contents of the prism. Specific gravity is estimated by the usual instrument at 17.5" C. with a correc-tion of =t0*0002 for each degree C.above or below that limit. Tables of estimations made with the Tornoe instrument and by the direct method by Fernbach Kjeldahl and Prior show that the differences between the two fall within the limits of experimental error. c. s THE ANALYST. 297 Sugar Estimation by the Kjeldahl Process. Bruhns. (Centralbl. Zuckerhd. , 1898 vi. 817 and 895; through Chem. Zeit. Rep. 1898 229.)-When Kjeldahl’s inethod of estimating sugar is adopted for mixtures containing cane sugar the copper thrown out of solution by the cane sugar is so much more copious that other things being equal 200 milligrammes of metal axe only about equivalent to 44 milligrammes in the Soxhlet process. This depends on the longer boiling and the greater alkalinity of the modified Fehling’s solution-two factors which Kjeldahl has completely over-looked.It therefore leads to quite erroneous results in the analysis of raw sugar and articles of food etc. ; and before it could be made serviceable would require thorough investigation. I t is certainly precluded from ranking as an official method. (See also ANALYST xxiii. 271.) F. H. L. Determination of Methoxyl. G. Gregor. (Monatshefte f iir C1wnie xix. 116.) -The author introduces sundry modifications in Zeisel’s method for the determination of methoxyl (ilfonatsliefte fiir Chemie 1885 989 ; ANALYST xi. 119) with the object of rendering it easier and quicker of execution and more suited to technical purposes. I n the first place he abolishes the direct gravimetric determination of the silver iodide substituting for it the equally exact but quicker volumetric method of Volhard.Next he replaces the neutral silver nitrate solution of Zeisel’s original method by a, solution acidified with nitric acid. As Zeisel himself observed not only does the precipitated silver iodide carry down a certain quantity of silver nitrate but the silver nitrate solution contains traces of silver iodide. As a consequence the precipitate and solution according to Zeisel’s procedure require to be separately treated the former by agitation with water to extract the silver nitrate and the latter by evaporation to expel the alcohol after diluting with water and acidifying with dilute nitric acid. By the use of a silver nitrate solution acidified with nitric acid the necessity for such separate treatment is avoided for although the silver iodide carries down with it a little silver nitrate this is easily washed out with water.Lastly the author prevents the reduction of silver nitrate which takes place in the tube which dips into the alcoholic silver nitrate solution of the first flask by employing a solution of potassium carbonate and arsenious acid instead of amorphous phosphorus. To suit the volumetric method of Volhard the author uses an alcoholic i$ silver nitrate solution standardized with a & potassium thiocyanate solution. For the determination 50 C.C. of this solution (acidified with a few drops of nitric acid free from nitrous) are placed in the first flask and 25 C.C. in the second. When the reaction is complete the clear fluid is decanted from the silver iodide into a 250 C.C.measuring-flask the precipitate washed the washings added to the flask and finally the silver nitrate in the second flask added also. The whole is then made up to 250 C.C. with water mixed filtered through a dry filter and 50 C.C. OF 100 C.C. acidified with nitric acid free from nitrous acid and titrated with potassium thio-cyanate with ferric sulphate as indicator. The following comparative results are given 298 THE ANALYST. Substance. Resacetophenone niono-ethyl ether C,H,O - (OC,H,) Resacetophenone mono-Monoethyl - p - resorcylic Resacetophenone %i&hyl methyl ether C8H70 - (OCH,) acid C,H,O - (OC H,) ether C,H,O(OC,H,), C,H,03(0C,H,)2 Dioxyethylbenzoyl for-mic acid Phenacetin C8H,NO( OC,H,) Origin.a-c $ 3 3 & Com-mercial product ! Required theoreti-cally. 25% OC2H.5 18.67% OCH, 24.72% OC,H, 43.26% OC2H5 37.81% OC,H, 25.13% OC,H, Gravimetric. I , Quantity taken. Gramme. 0.2165 0.2515 0.21 0'2595 02734 0.3445 Iodide of Silver hamme. 0'284 0.36 0.271 0.581 0.538 0.450 Found. Volumetric. - Quantity taken. Gramme. 0-186 0.25 0.263 0.229 0.2125 0.3445 Analysis of Lysol Creolin and Similar Preparations, ?otassiun Tliio-cyanate required [or 50 C.C. filtrate. C.C. 12-95 12.0 12.1 10.05 11.45 11.15 Found. 24.79% OC,H, 18.60% 24.80% 42-73x OC,H, 37.58% OC,H, 25.14% OC,H, OCH, 0CZH.j H. H.B. S. H. Ditz and R. Clauser. (Chenz. Zed. 1898 xxii. 732.)-An analysis of such products as lysol and carbolic soap involves the separation of phenols hydrocarbons and fatty acids one from another ; and the present process depends on the fact that barium oleate is quite insoluble in hot and cold water and only slightly soluble in 50 per cent. alcohol whereas barium phenolate dissolves in 40 per cent. of its weight of water at 100" C. the orthocresylate in 150 per cent. the paracresylate in 320 per cent. while the rare metacresylate is very soluble. Barium oleate however being somewhat uncertain in composition cannot be weighed as such it is necessary again to liberate the oleic acid. Moreover the fatty acids in lysol etc. are not pure oleic but contain stearic and palmitic as well the barium salts of which are partly decomposed by water Nevertheless preliminary experiments have shown that working on lysol, which usually contains about 40 per cent.of fatty acids and 40 per cent of phenols, the amount of the former recovered is only 0.5 per cent. too low and this is a deficiency of no importance in the present investigation, To carry out the analysis 5 grammes of lysol are dissolved in 100 C.C. of warm water 20 or 30 C.C. of 10 per cent. caustic soda added and the mixture extracted two or three times with ether to remove the hydrocarbons. The ethereal solution is washed with very weak soda and the latter combined with the bulk of the aqueous liquid ; the ether is dried with solid potash cautiously evaporated and the residue dried over sulphuric acid to constant weight.The aqueous solution is carefully freed from ether on the water-bath neutralized with hydrochloric acid cooled com-pletely (this is most important) treated with excess of barium chloride and a quantity of baryta-water roughly equivalent to the phenols present. The mixture i THE ANALYST. 299 filtered quickly avoiding unnecessary exposure to the air the precipitate washed with baryta-water then cold and finally hot water rinsed back into the original beaker decomposed with 1 1 hydrochloric acid and thrown on to the first filter again. The oleic acid is washed with hot weak acid till free from barium with water till free from acid dissolved in absolute alcohol and ether and evaporated to constant weight at 100" C .The filtrate from the barium precipitate may be acidified extracted with ether, and the phenols recovered by evaporation; but it is better to operate as follows I n a convenient fraction of the acidified liquid the mixed phenols are determined by the Koppeschaar method (calling the bromine absorption calculated on the whole bulk A grammes). Another portion is extracted with ether the solvent evaporated and the residue dried for two or three hours at 100" to 110" C. (loss by volatilization is of no consequence in this test). I t is then dissolved in caustic soda or baryta and titrated as before calling the weight of the whole residue a grammes and its bromine absorption B. The weight of the lysol originally taken for analysis being C grammes the percentage of phenols is given by the formula : 100 x A x u ~- B x C F.H. L. Volumetric Determination of Nitrophenol Derivatives. L. Schwarz. (&?onut-shefte fiir Cl~enzie xix. 13Y.)-The author has carried out experiments upon the deter-mination of the nitrophenol derivatives by taking advantage of the liberation of free iodine resulting from the action of potassium iodide and iodate. The iodine was determined volumetrically by a & sodium thiosulphate solution freshly standardized before each series of experiments was commenced. The starch emulsion was prepared as recommended by Zulkowski and Topf (Zeit. flir aiznlyt. ClLemie xxvi. 138) by diluting a glycerin emulsion with solution of common salt. The results show that tri- and tetra-nitro derivatives can be determined in this way without particular regard being paid to the length of time allowed for the action; but that in the case of dinitro-derivatives substitution of iodine takes place if the heating is too long continued and for the same reason mononitro-derivatives cannot be determined in this way at all.Experiments with tribromophenol and with tetrabromfluorescin (eosin) led to the conclusion that these substances are not adapted to this method of determination. H. H. B. S. The Composition of the Ash of some Raw Tanning Materials. W. I(. Alsop and J. H. Yokum. (Jozw. Amer. Chewz. Soc. 1898 xx. 338-340.)-With the object of obtaining fuller information on the composition of some of the common sources of tannin the authors have made complete analyses of a large number of samples the average results of which are given in the subjoined table.The method by which the tannin was determined was that of the Association of Official Agricultural Chemists 1897. The total extract was obtained by extracting the bark with boiling water and evaporating the solution the residue in the extractor, returned as cellulose and insoluble matter being determined by difference. The soluble solids were the solids of the extract soluble at 18" C. and the red colourin 300 THE ANALYST. matter the difference between the total and the soluble solids. The non-tannins (mainly glucosides of unknown composition) consisted of the soluble solids not absorbed by hide. The very much larger amount of ash in the oak than in the hemlock bark was due to the fact that the latter does not grow on a limestone soil. Chefitnut Bark. No. of samples . . . . 118 Total extract . . . 24.69 Total soluble solids . 20.36 Red colouring matters . 4.33 Non-tannins . . . . 9-81 Tannins . . . 1055 Moisture . . . 10.8.1, Cellulose and insoluble matter . . 64.46 .Ish . . . . . 6.02 Carbon . . 0.77 Sand and silicic acid . 2.34 Sand . . . --- SiO . . A 4 0 + Z'e20.; . . . . 0 08 MgO . . . 1.18 K,O . 2.95 MnO . . . 1% CaO . . . . . 52.63 Na,O . . . . . 0.63 c1 . . . 0.44 so . . . 0.17 co . . . . . 36.51 P,Oj . . . . . 0.64 Chestnut h r k . 117 19-76 16.26 3 50 8.21 8.05 9.73 70.51 8.05 0.11 3.33 __ -0.86 0.33 58.24 1-77 2.62 0-40 0.10 0.12 1.13 31-47 99.62 100.49 Hemlock Bark. 81 19.33 15.40 3.93 6.74 8.66 11.57 69.10 1.65 0.23 1.12 0.78 3 -07 2.26 52-59 1 -98 6.02 0.27 0.20 0.82 2.62 97-66 99.55 -Hemlock Hark. 50 19-96 16.11 3.85 6-44 9 6 7 13-75 66-29 1.45 0.59 3.53 2-84 3-86 4.09 49-35 2.92 7.64 0.95 -0.24 { 1 -88 2-94 I9.10 99-93 Quebrach Oak-bark Wood. Extract. 1 1 34-80 46-92 19.20 45.96 5.60 0.96 3 64 20.29 15.56 25.67 11-60 53.17 63 *60 -0.88 1-35 0.11 1-57 0.88 1.88 -0 *64 0.1 0 61-27 4-56 0.24 1.22 un det er inined 1.11 0.50 -5.59 2.21 19.15 2.38 29.44 1.01 unde ter-mined 2.86 3-72 un de ter-28'30 { mined 98.93 .-c. A. AT
ISSN:0003-2654
DOI:10.1039/AN8982300284
出版商:RSC
年代:1898
数据来源: RSC
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5. |
Inorganic analysis |
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Analyst,
Volume 23,
Issue November,
1898,
Page 300-305
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300 THE ANALYST. INORGANIC ANALYSIS. Estimation of Lead i n its Ores. L. Schneider. (Ocstcw. Z e d s . Berg. PL. H;?tteizzo., 1898, xlvi., 431 ; through Clzem. &?it. Rep., 1898, 212.)-The author has investigated the inflnence of several substances upon the degree of insolubility of lead sulphate. He fiuds that tartaric, and more particularly nitric, acids raise its solubility in water ; and that, although the presence of sulphuric acid, tartaric acid, or ammonium sulphate diminishes the solvent action of the nitric acid, yet lead cannot be completely precipitated unless the latter forins less than 1 per cent. of the liquid. He suggests the following process for the analysis of lead ores : 1 gramine is boiled for ten or fifteen minutes with 5 C.C. of strong hydrochloric acid, when 5 C.C.of strong nitric acid are added, and the mixture heated till the brown vapoursTHE ANALYST. 301 disappear. The lead salt is dissolved in 10 grammes of tartaric acid and 25 C.C. of water, and treated with 25 C.C. of strong ammonia, The insoluble residue consists only of quartz and barium sulphate. The filtrate, diluted to 300 c.c., is warmed with 50 C.C. of 1 : 1 sulphuric acid, the precipitate washed with 1 per cent. acid, dried and weighed. If all these conditions are adhered to, there is no necessity to drive off the nitric acid, because in the final filtrate and washings, which amount to about 500 c.c., 0-003 gramme of lead sulphate always remains in solution, and the obvious correction can easily be made. F. H. L. Volumetric Estimation of Lead Peroxide by Means of Arsenious Acid.C. Reichard. (Chem. Zeit., 1898, xxii., 774.)--Although lead peroxide is not attacked by an aqueous or ammoniacal solution of arsenious acid, in strong caustic soda, solution at the boiling-point it is quantitatively reduced to monoxide : 2Pb0, + As,O, = 2Pb0 + As,O,. Since the substance is largely used as an oxidizer in the nianufacture of dyes, the percentage of available oxygen it contains is often the most important factor, and to save calculation, therefore, the analysis may be conducted exactly as follows: The peroxide is brought to a fine powder, being preferably passed through a cloth ; 0.1 gramme is weighed out, and introduced into a known excess of a solution of arsenious aci& in concentrated caustic soda containing 0.0099 gramme of As,O, (= 0.0016 gramme of oxygen) per C.C.The whole is boiled with further additions of highly concentrated alkali till the liquid is colourless or but faintly yellow. It is then diluted, acidified with sulphuric acid, and the amount of arsenious acid remaining estimated by titration with permauganate. If preferred, the neutral solution may be filtered, treated with sodium bicarbonate, cooled, and similarly titrated with iodine and starch. F. H. L. Examination of Alloys containing Lead and Antimony. A. Fraenkel. iWitthei1. t c c l m Gew. Il.jrz~s. Viema, 1898, viii., 334 ; through Clzem. Zcit. Rep., 1898, 229.)-Alloys which contain lead, copper, and phosphorus as well as tin and antimony are attacked with nitric acid, the residue fused with caustic soda in a silver crucible, the melt extracted with water, diluted with one-third its volume of alcohol, and filtered after standing for twenty-four hours.The filtrate (F) contains sodium stannate and phosphate, and the whole of the lead undissolved by the nitric acid at first ; the residue (R) contains the antimony and copper. I n (F) the lead is precipitated with sulphuretted hydrogen and determined as usual ; the filtrate is treated with sulphuric or acetic acid to throw down tin sulphide, mhich is converted into oxide and weighed as such. The filtrate from the tin is evaporated and the phosphoric acid estimated. (R) is dissolved in hydrochloric and tartaric acids, and precipitated with sulphuretted hydrogen ; the antimony sulphide is dissolved by digestion with ammonium sulphide, filtered from the copper, thrown down together with some sulphur by means of acid, collected on a tared filter, and the antimony determined in a portion by ignition in a current of carbon dioxide.The original nitric acid solution is investigated in the ordinary fashion. P. H. L.302 THE ANALYST. The Determination of Lead in Alloys. W. E. Garrigues. (JOZLVZ. Anzer. Chem. SOC., 1898, xx., 508-510.)-The following method is based on the fact that lead chromate is insoluble in ammonia, whilst copper chromate i s readily soluble. Where applicable, it is much more rapid than precipitation of the lead as sulphate. The solution of the lead and copper in nitric acid is mixed with potassium bichromate in excess, followed by a large excess of ammonia.The liquid is heated until the supernatant liquid becomes clear, and the precipitate of lead chromate collected in a Gooch crucible containing a single disc of filter-paper as the filtering medium, washed with dilute ammonia, hot water, and alcohol, and dried in the wat er-oven. This method is essentially a separation of lead from copper and zinc; but when antimony, bismuth, or iron are present, the sulphate method must be employed. I n determining lead in the presence of antimony, it is possible to prevent the small quantity left in the filtrate from the tin from being precipitated with the lead sulphate by adding a large amount of sulphuric acid, diluting sparingly, and filtering as rapidly as possible. A rapid modification of the sulphate process, in which the lead is obtained without previous removal of tin, is described in the form of an account of an experiment : Half a grainme of solder, containing, according to the sulphate and chromate determinations, 58.83 and 58.80 per cent.of lead respectively, was oxidized with nitric acid, 20 C.C. of strong sulphuric acid added, and the liquid evaporated until dense fuines appeared. The metastannic acid was completely dissolved. After adding 80 C.C. of cold water, the solution was well stirred and the lead Rulpbate collected on a Gooch’s filter. The filtrate was made alkaline with ammonia, and sulphuric acid added until the liquid turned inethyl orange decidedly red. The liquid was boiled, and the voluminous white precipitate collected on a filter, ignited in a strong blast, and weighed as stannic oxide.The amount of tin calculated from the result was 41-1 per cent. If more than 80 C.C. of water were used for the dilution, or if the solution was left on the water-bath for an hour or two, the tin began to precipitate slowly. The quantity of lead thus found was 59 per cent. C. A. Rl. Estimation of Nickel in the Presence of Iron. B. Neumann, (Chenz. Zeit., 1895, xxii., 731.)-Five grainmes of steel borings are dissolved in dilute sulphuric acid, and the carbon and iron oxidized with bromine, nitric acid, or preferably hydrogen peroxide. The solution is brought into a 500 C.C. flask, ammonium sulphate added, the iron precipitated with ammonia, the liquid boiled, excess of ammonia introduced, and after cooling diluted to the mark.One hundred C.C. (= 1 gramme) are filtered off, diluted slightly, warmed and treated with a current of 1 or 2 amperes at 3.4 to 3.8 volts for one-and-a-half to two hours. The space occupied by freshly- precipitated ferric hydrate is not known, but in ordinary steels the error thus caused will not exceed 0.5 per cent. of the nickel obtained. I n steels rich in nickel, where only 0.5 gramme is taken for electrolysis, it will be about 0.2 per cent, ; and in nickelTHE ANALYST. 303 ores, etc., containing 50 or 60 per cent. of iron, not more than 0.2 or 0.3 per cent. Nickel ores are attacked first with hydrochloric acid, then with nitric, and evaporated with sulphuric acid till white fumes appear. The heavy metals are thrown down with sulphuretted hydrogen, excess of the reagent removed by heat, the liquid oxidized with bromine or hydrogen peroxide, and 100 C.C.of the solution ( = 1 gramme of material) treated as before. Cobalt remains in the liquid, and is deposited with the nickel. One sample of nickel-steel which gave 4.12 per cent. of Ni when the iron was removed by fourfold precipitation gave 4-02 per cent. of N i by the author’s process ; electrolysed in presence of the ferric hydrate, the yield was 4.00 per cent. (corrected). A specimen of nickel ore examined by the author’s method gave 6.02 per cent. of Ni+Co; four precipitations of the iron gave 6-15 per cent. of Ni+Co; electro- lysis without removal of the iron gave 5.98 per cent. of Ni+Co (corrected); Rothe’s process (extraction of the hydrochloric acid solution with ether, to dissolve iron and cobalt) gave 5.60 per cent.of Ni. The proportion of cobalt, specially estimated with nitroso-/I-naphthol, was 0.50 per cent. F. H. L. The Use of Hydrofluoric Acid in the Determination of Manganese in Iron and Ores. A. P. Ford and I. M. Bregowsky. (JOZWL. dmer. Chenb. SOC., 1898, xx., 504-506.)--In order to avoid the evaporation which is necessary when hydro- fluoric acid is used in the determination of manganese in high silicon pig-irons, the authors have made experiments on the direct use of the acid with eventually successful results. The iron is dissolved, and the manganese precipitated with potassium chlorate. As soon as the precipitation is complete a few drops of hydrofluoric acid (the quantity depending on the amount of silicon present) are added, and the liquid boiled until the hydrofluoric acid is expelled.h little more potassium chlorate is then added (about 1 gramme), and the liquid concentrated as much as desired, The solution filters rapidly, and the graphitic carbon will be found to be almost conipletely oxidized owing to the removal of the enveloping silica. Similarly, in the case of manganese ores a few drops of hydrofluoric acid are added aftey the precipitation of the manganese with potassium chlorate, and if the first addition does not clear the solution in a minute or two, a few more drops are added. With a little practice, the amount required can be judged by the amount of floating gelatinous silica, AS to the action of the acid on the beakers, the authors state that, though they become opaque, their life is but little diminished. It is, however, advisable to keep a number of beakers apart for manganese determinations only.C. A. M. Aluminium used as an Electrode. G. J. Hough. ( J o w ? ~ . L!vp*. Chem. soc., 1898, xx., 302, 303.)-The author states that aluminium can replace platinum as an electrode to a limited extent, It can be used as the cathode with nitric acid solu- tions without being affected, but cannot be used as the anode, for at that pole it is readily oxidized and dissolved. I t is attacked by the free acid in sulphate or chloride304 THE ANALYST. solutions, but can be employed when these are converted into the double oxalate of potassium or ammonium, as recommended by Classen. It is not attacked by cold solutions of potassium cyanide or oxalate, even under electrolytic action.Not being acted upon by hot or cold nitric acid, the metals deposited on it should readily be dissolved, but the author has not yet tested its applicability thoroughly and minutely, except in the case of copper analysis. Being so much lighter than platinum, its use reduces the chance of error in weighing the deposited metal, while its cheapness is a, further advantage. C. A. M. Detection of Normal Carbonate i n Bicarbonate of Soda. N. Kubli. ( A d / . Plmrm., 1898, ccxxxvi., 321 ; through Cheni. Zed. h'ep., 1898, 228.)-A 0.1 per cent. solution of quinine hydrochloride is not precipitated by sodium bicarbonate unless more than 2 per cent. of normal carbonate is present.To apply the test, 3 grammes of bicarbonate are dissolved in 50 C.C. of water at a temperature of 5" or 6" C., without agitation, in a closed vessel. On adding an equal volume of the quinine reagent, the mixture should remain clear. F. H. L. Volumetric Estimation of Nitric Acid. W. Ackermann. (Che?n. Zeit., 1898, xxii., 690.)-This process depends on the reduction of nitrates to ammonia by means of ferrous hydrate. One gramme of potassium nitrate, 30 C.C. of caustic soda (specific gravity 1-33), and 40 gramines of crystallized ferrous sulphate, are placed in a 500 C.C. flask with 160 C.C. of water ; a small quantity of reduced iron is added to assist the boiling, and the liquid is distilled into standard acid in the usual fashion. The operation proceeds quietly, and is generally finished in half an hour ; but the complete evolution of the ammonia may easily be ascertained by removing the beaker containing the acid, washing the outside of the condensing tube, and testing the next 30 or 40 drops of distillate with litmus-paper. Should this prove to be stilk alkaline, more water may be added to the flask, and the distillation continued slowly; but as it is a sign that the reduction has not been successful, it is perhaps better to repeat the whole analysis.Blank experiments are necessary to estimate the amount of nitric acid in the several reagents, and in order to keep the correction as small as possible, the ferrous sulphate should be prepared from iron wire and pure acid, and good commercial caustic soda employed instead of the pure '' article.The above- mentioned proportion of water may be doubled or trebled if desired, but larger quantities tend to imperfect reduction, because on prolonged hoiling and before suitable concentration is reached the ferrous hydrate loses its activity. The weight of caustic soda should be kept as specified ; that is to say, it should form only a slight excess over the amount needed to decompose the ferrous sulphate. Alkali chlorides, sulphates, and acetates do not interfere with the process ; tartrates hinder the reaction ; and phosphates, as existing in artificial manures, involve the following modification: The solution of the fertilizer is mixed in the distilling flask with sufficient calcium chloride solution of known strength to convert the whole of the soluble phosphorus into tribasic phosphate; the alkali is then dropped in with constant agitation, until an excess equivalent to 2 C.C. of the calcium chloride is attained; the ferrous sulphate and metallic iron are next added; theTHE ANALYST. 305 liquid is made up to 170 C.C. (to allow for the extra viscidity caused by the calcium phosphate), and the analysis is finally conducted as before. Figures quoted by the author show that, in working on 1 gramme of saltpetre under ordinary conditions, the variations in the end results will not exceed 1 or 2 milligrammes. F. H. L.
ISSN:0003-2654
DOI:10.1039/AN8982300300
出版商:RSC
年代:1898
数据来源: RSC
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6. |
Apparatus |
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Analyst,
Volume 23,
Issue November,
1898,
Page 305-305
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摘要:
THE ANALYST. 305 APPARATUS. A New Vacuum Filter Flask. R. Walther. (Pham. Central. H., 1898, xxxix., 550; through Chenz. Zeit. Rep., 1898, 209.)-The construction of this apparatus is shown in the sketch, the shaded portion being a hollow (pneumatic) rubber ring filled with air, which fits any flask or funnel indifferently, and makes a tight joint by its own compression. F. H. L. Apparatus for the De- termination of the Reich- ert - Meissl Number of Butter. M. Siegfeld. (Chem. Zeit., 1898, xxii., 738.) - In the Milchwirth- schaftliche Institut at Ha- ineln a pipette is used for measuring out the quantity of butter-fat required for this process, which, when in a n i pula t e d uniformly, always delivers between 4.96'7 and 5-045 grammes. The maximum variation, therefore, corresponds to a difference of 0.2 or 0.3 in the Reichert - Meissl number ; and this is quite insignifi- cant in comparison with other sources of error. For the filtration of the fat and for keeping the pipettes warm a special water-bath, as illustrated herewith, is em- ployed. The thermometer has a red mark at 50" C. to make it more conspicuous; but for ordinary purposes the temperature needs only to be maintained between 45" and 55" C. F. H. L.
ISSN:0003-2654
DOI:10.1039/AN8982300305
出版商:RSC
年代:1898
数据来源: RSC
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7. |
Reviews |
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Analyst,
Volume 23,
Issue November,
1898,
Page 306-308
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306 THE ANALYST. R E V I E W S . A SHORT COURSE OF INORGANIC QUALITATIVE ANALYSIS FOR ENGINEERING STUDENTS. By J. S. C. WELLS, Ph.D., Instructor in Analytical Chemistry, Columbia University. London : Chapman and Hall. 1898. The object of this work is to give a ‘‘ short but thorough ” course in inorganic qualitative analysis for the use of students who have but a limited time to devote to the subject. There is no doubt that the student who may use Mr. Wells’ book with zeal and discretion will necessarily gain a valuable knowledge of elementary qualitative analysis, but the work is no royal road to an understanding of the subject ; and although excellent in many respects, is not without serious defects. To begin with some of its excellences-equations are freely used, the tables of separation are well printed, arranged, and expressed, and the tables of reactions representing skeleton schemes of separation (using formula3 only) form a valuable and somewhat original feature.For the rest, it differs but little from the innumerable works of this kind, and lacks the masterly treatment which we find in such manuals as those of Clowes and Coleman, Tilden, or Thorpe and Muir. It is admittedly based on Fresenius, who has been curtailed and improved upon in a somewhat wayward fashion. The descriptions of reactions are too lengthy and involved, and there is much unnecessary waste of space in text and tables, so as to leave an impression that the book would be equally useful if reduced to 150 pages, instead of the 300 of which it consists at present. H.W. H. New York : John Wiley and Sons. A LABORATORY GUIDE IN QUALITATIVE CHEMICAL ANALYSIS. By H. C. WELLS, M.A., Professor of ,4nalytical Chemistry and Metallurgy in the Shefield Scientific School of Yale University. Mew York: John Wiley and Sons. London : Chapman and Hall. 1898. This work is the printed presentment of a method of instruction which has been used by the author for fourteen years. Fresenius, who might, indeed, be called the primogenitor of analytical text-books, has again been largely drawn upon ; but changes have been made where the author has considered them “ advantageous,” and a “ few novelties ” have also been introduced. One of these is a rearrangement of Fresenius’ groups, which seems liable to render confusion worse confounded.The work has but little to recommend it, and its sphere of usefulness might be greater if it were much condensed. The main idea seems to be an attempt to make the student evolve analytical methods out of his own inner consciousness by a series of elaborate exercises, which are by no means of a practical character. Take, for instance, the first exercise, where the pupil is directed to find by experiments which, out of twenty-seven solutions (of the common metals), yield a precipitate with hydro- chloric acid. The simple reactions of this group are dealt with at inordinate length, and similarly with all the groups through fifty-six long pages. Blowpipe tests are not considered, as L 4 they are usually studied in connection with determinative mineralogy ”; but Fresenius may be consulted. Next following we have directionsTHE ANALYST.307 for making reagents which are used in the first part. The ensuing chapter, on ionization and ions, is far too brief to be of any real value or interest; and after various chapters on the classification of salts and chemical equations, etc., we are finally, on p. 101, introduced to the reactions of the metals and acid radicles ! The most original feature of the work consists in twenty pages of chemical labels at the end, arranged so as to be torn out for use in the laboratory. H. W. H. PRACTICAL ORGANIC CHEMISTRY : THE DETECTION AND PROPERTIES OF SOME OF THE MORE IMPORTANT ORGANIC COMPOUNDS. By 8. RIDESL, D. sc., F.1.C. Second edition. London: H. Ei. Lewis. 1898. Many students, and not a few teachers, will welcome the second edition of this useful and able little volume, which fills a, special gap in analytical text-books.It deals with a definite class of compounds in a direct and succinct fashion, which is extremely refreshing in comparison with the two last-mentioned works, with which it is only fair to say it has nothing in common. The reactions of several important organic compounds have been added, and note has been taken of alterations in the new British Pharmacopeia, but the size of the book has not been unduly increased. On one point only can we bring ourselves to disagree with Dr. Rideal, and that is as regards the omission of any scheme of analysis; such a scheme is, we think, much needed. A summary of distinctive tests for each group is, however, still included, and forms a, basis on which an earnest student may work out a scheme for himself. Although the work is specially adapted for the London University and other examina- tions, it will without doubt be appreciated by a wider circle of scientific workers.H. W. H. LABORATORY TEXT-BOOK FOR BREWERS. By LAWRENCE BRIANT. Second edition. Price 10s. 6d. net. (London : Fell and Briant.) The first edition of this useful work, which was published in 1884, was for a long time the standard book on the analysis of the materials used in the brewery; but as time went on, and in the meantime this department of chemistry progressed some- what rapidly, the work naturally fell behind the times. The new edition, which has been promised for a very long time, effectually disposes of this drawback, for it has been thoroughly brought up to date, and to do this effectually has necessitated the re-writing of the whole book.The new edition possesses all the good qualities of the- old, such as simplicity and clearness of style, and the student is greatly assisted by the examples appended to the description of the various analyses. A few statements have crept in which will need correction in a future edition, of which the following are examples : P. 4, d l Ungelatinized starch is not acted upon by diastase ”; p. 20, ‘‘Levulose oxidizes into saccharic acid by contact with dilute nitric acid”; p. 27, 1‘ Amido-acids are formed when amides are heated with a mineral acid.” However, these are trifles when compared with the otherwise excellent character of the information supplied, which will be found most useful to brewing analysts and students of brewing chemistry.W. J. S.308 THE ANALYST. TECHNICAL MYCOLOGY : THE UTILIZATION OF MICRO-ORGANISMS IN THE ARTS AND MANUFACTURES. By Dr. FRANZ LAFAR, with a Preface by Dr. ENIL C. HANSEN. Translated by CHARLES T. C. SALTER. Vol. I. : Schizoniycetic Fermentation. (London : Charles Griffin and Go.) This is the first time that mycology in its practical application to the arts and manufactures has been treated in a thorough and exhaustive manner. Such a book as this was urgently needed, for in recent years the subject on which it treats has made enormous advances; it is only when the whole of the instances are collected together that we realize how numerous the industries are in which micro-organisms play an important part.The introduction is divided into three parts; the first of these treats on the theory of spontaneous generation, and gives a historical rksuni6 of the various views on this subject which have dominated the scientific world from time to time. The author is of opinion that, though abiogenesis is yet unproven, it may not be impossible, The next division contains a short and similarly historical summary of the principal views which have been advanced in explanation of the phenomena of fermentation. Dr. Lafar defines this process as “ a decomposition or transformation of substances of various kinds induced by the vital activity of fungi.” The third division treats of the position of the organisms of fermentation in the botanical system.We now come to the body of the book, which is divided into sections. The first of these is devoted to a, description of the general morphology and physiology of the schizomycetes ; Section 11. to their general biology and classification; Section 111. treats on the methods of sterilization and for obtaining pure cultures ; the following section on the behaviour of the chromogenic, photogenic, and therinogenic bacteria. The remaining five sections are mainly devoted to the consideration of those micro-organisms which are immediately concerned in, or affect, processes carried out in manufacturing operations, such as the ( ( retting ’’ of flax, souring of cream, the fermentation of the liquors used in tanning, the ripening of cheese, the manufacture oE vinegar, and many others. Froin this some idea inay be gained of the comprehensive nature of the work, which is, with reference to these subjects, a perfect mine of wealth. Without doubt the book is indispensable to all who are engaged in any of those industries in which bacterial fermentations are concerned, and for the scientist it fornis a, valuable work of reference ; so good is it that we look forward with something like impatience for the appearance of the second volume, which will treat on the Saccharo- mycetes and the fermentations they induce. The book is well printed, the illustrations excellent, and, altogether, it is got up in handsome style. The translator, Mr. Salter, is to be congratulated on the exeellent manner in which he has accomplished his task. Price 15s. W. J. S.
ISSN:0003-2654
DOI:10.1039/AN8982300306
出版商:RSC
年代:1898
数据来源: RSC
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