摘要:

THE ANALYST. JANUARY, 1885. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. AN ordinary meeting of this Society mas held a t Burlington House, on Wednesday, the 17 th December last, Mr. C. Heisch, vice-president, in the chair. The minutes of the previous meeting were read and contirmed. Messrs. ICingzett and Johnstone mere appointed auditors. The Scrutineers, having opened the ballot papers, reported that the following gen- As Members--II. F. Cheshire, F.C.S. ; Sandford Moore, M.B. ; D. A. Sutherland ; As Associate-J. I<. C‘olmell, Assistant to Mr. Wynter Blyth. The following gentlemen were proposed, and will be balloted for at the next As Members-TV. Newton, Analyst, London; C. A. Smith, Analyst, Sydney, New As Associate-Mr. Bredon, Assistant to Dr. Bernays. The following papers were then read and discussed :- I ( On the Calculation of Milk Results,” by C .Reisch, F.I.C., F.C.S. l L Some Analysis of Pure Milk,” by C. W. Stephens. ‘( On a Chalybeate Water and Saline Deposits from Southbourne-on-Sea,” by C. T. Kingzett, P.C.S., F.I.C. The paper announced to be read by Mr. Hehner, on ( ( Honey and Wax from Sugar- Fed BCCB,” vas postponed, owing to the author’s absence, caused by recent domestic affliction. At the conclusion of the ordinary meeting, an extraordinary one mas held, for the purpose of considering an alteration in the rules of the Society, whereby all past Presidents of the Society now, and for the future, would be eligible for re-election from year to year as vice-presidents and ex qflcio members of the Council, in addition to three tlemen had been duly elected :-- R. C. Woodcock, F.C.R. meeting :- South Wales.2 THE ANALYST. other vice-presidents, who have not yet passed the chair, to be elected annually without -any reduction of the number of ordinary members of Council. Dr. Dupe, in proposing the alteration, said it was desired to avoid the chance of all the London members who had passed the chair, being removed from the Council, and this would happen if some such alteration mere not made, unless they were con- tinually re-elected, and so prevent new blood being introduced on the Council; but it mas necessary to have a large number of London members on the Council, or there mould never be a quorum. It was not likely that the past presidents mould swamp the ordinary members-in the Chemical Society they had such a rule--and there were now only 17 vice-presidents after about 44 yems. The alteration was unanimously agreed to.

ISSN:0003-2654    

DOI:10.1039/AN885100001b

出版商:RSC    

年代:1885

数据来源: RSC

摘要:

2 THE ANALYST. NOTES FROM THE PRACTICE AT THE SOUTH LONDON CENTRAL PUBLIC LABORATORY. BY JORN MUTER, Ph.D., P.I.C. CHEESE ANALYSIS. (Aead 6ejore the Society at the Heeting on 19th November, 1884.) A GOOD deal has been written from time to time on this subject, and both processes and typical a.nalyses have been given in the recent works of Dr. Bell and Mr. Wynter Blyth. There is, therefore, perhaps, nothing very novel in what follows, but as the analysis is of growing importance, owing to the increasing importation of oleomargarine cheese into this country from America (which specially finds its way into the shops in the spring months), I have thought it well to publish our method of working, together with a series of the results of the examinations of such of the various cheeses of commerce as have lately come under our notice : the actual analyses quoted being chiefly the work of Rlr.Jose M. Vhrgas. The first point is so to deal with the sample, that the small quantity (rarely exceed- ing & lb.), usually trought by the Inspector, shall suffice for everything. The only adulteration ever now found in cheese being the introduction of oleomargarine, the beat thing is at once to separate the fat and to make a preliminary test by Koettstorfer’s process. The simple method by gravity is not available with cheese, unless we can work upon a much larger quantity, and besides, the solvents used t o extract the fat are apt, unlesw great care be exercised, to render it a little too light. While extracting the fat, it is well to obtain not less than 6 grammes, so that there will be enough for all future prooeedings, should this test turn out unfavourably.The poorest cheese in fat in the market is English cream cheese, and this never contains less than 15 per cent. We, therefore, work upon 45 grammes of cheese, to be sure that we obtain enough fat, thus consuming a little over 14 ounces of our sample. There are three steps taken in this part of the analysis, as follows :- 1. Betemhation of the tota2 acidity ia the presence of alcohoL-This is necessary, as a guide, in future parts of the work, and is done by rubbing up 5 grammes of the cheese (broken up small if a hard one) in a small mortar, with 10 C.C. of alcohol, and a few drops of alcoholic solution of phenol-phthalein, and titrating with decinormal soda, untilTHE ANALYST.3 a faint pink colour is obtained, vhich does not disappear on farther rubbing. The number of C.C. of soda used is noted. 2. Extraction of the fat.-45 grammes of the cheese are melted in a basin on the water bath, and 8 granimes of pure sand having been stirred in with a thick glass rod (or rather a glass pestle, somewhat longer and thinner than usual), sufficient decinormal soda is added from ft burette, to exactly neutralize all acid ; this amount being calculated from experiment No. 1, above described. Another 8 grarnmes of sand are then stirred in, and the whole dried on t>he water bath, with frequent stirring. When dry, the con- tents of the basin are broken up, transferred to a Xoxhlet extractor, and acted upon therein by petroleum spirit, which has been redistilled under 200° F.When the extraction is complete, the petroleum is distilled off, and the fat dried by heating to 212O F. with a current; of air passing through the flask containing it, until not the slightest vestige of odour of petroleum remains. In the flask will now be left a mini- mum of 6 grammes of fat. 3. Ascertninipzg the amicnt of alkali comzci~zert iit si!pon@iny the fat.-A small light wide-mouthed flask of a little over 100 C.C. capacity, is thoroughly dried and tared on the balance, and about 2 grammes of the melted fat are poured in, so that all collects exactly in the bottom of tho flask, and no drops fall upon th; neck or sides. The whole is then weighed, and the tare having been deducted, the balance is the weight of fat taken for analysis.Another similar flask is also got ready for a check blank experiment, without any fat. Into each of these flasks 25 c,c. of a normal solution (56 grms. per lifre) of potassium hydrato in alcohol of *835 sp. gr., are very accurately measured by dropping it straight into the bottom, and the mouths of the flasks having been lightly closed by placing a watch glass over each, the contents are brought to the boil, and kept very gently boiling for fifteen minutes. 10 C.C. of alcohol, and a few drops of alcoholic solu- tion of phenol-phthalein are then added to each flask, and the contents are titrated with seminormal hydrochloric acid (18.25 grnis. real HC1 per litre), until the colour just changes from pink to yellow. By mutual calculation of the check blank experiment, and the analysis, the amount of real ICHO consumed in saponifying the fat is obtained, and expressed in millegrammes for each gramme of fat taken. Genuine cheese fat should not consume less than 220 millegranimes of KHO for each gramme started with.That this is so, will be evident froiii the following table, showing the mean of many analyses of the cheeses named. Cheddrir ,. '. .. .. * . ., 227.5 Double Glo'ster , , * . * . .. ,. 229.3 Stilton . . * . .. .. .. .. 231-7 English Cream . , * I .. .. L . 220-0 Dutch .. .. . I I . ,. .. 228.7 GruyEre . , I . .. .. , , 228-0 Rochefort . , .. .. *. .. ,. 229.3 Camembert ,. .. * . .. a . , . 229-0 Bondon ,. .. .. .* a . ). 228.0 American , . * t .. .. ... ,. 220-2 If, however, thc ICE10 consumed exceeds that limit the cheese is probably adulterated, and it is then necessary to confirm by taking the soluble and insoluble fatty acids, using for that purpose the rest of the extracted fat.As a check the--____ 4 THE ANALYST. adulteration may be calculated by Koettstorfer's formula, taking the lowest possible estimate of genuine cheese fat thus (71 = millegrammes KHO consumed)- ( 2 2 0 4 ) x loo=$ (220-1 95.5) but we never report on this test alone without confirming by taking the fatty acids. We prefer to use seminormal acid, as the readings are more clelicttte than with the normal. The addition of the extra 10 C.C. of alcohol after saponificatioiz is also an improvement, as there is then never any separation of fatty acid during the titration.The alcoholic potash should be measured from a special burette fitted with a glass stopcock, and provided with a float made to work in a solution of a like specific gravity. The potash solution in alcohol may be made by starting with rectified spirit of -835 gravity and dissolving such an amount of coiiimercial pot ash (usually about 60 grammes) as will bring it (when cold and after decanting from the sediment) to a specific gravity of ,987. I t will then be ready for testing against the seminormal acid and diluting to the accurate point. The best may of making the acid is to take 60 C.C. of the ordinary pure hydrochloric acid of the B.P., and make it up to one litre with water ; 100 C.C. of this acid is then t o be exactly neutralized by pure sodium hydrate, and titrated mith deci- normal solution of argentic nitrate with potassium chromate as ail indicator, and the amount of dilution required having been calculated from this result, the finished acid is once more tested to ensure accuracy.If the cheese should give unfavourable indications with Koettstorfer's test, then we proceed to :- 4. The estitnation of the sold& aszd imolublo fcdty flcias.-on this point our views have undergone some modificat'ion since I first wrote about it in 1877. We now start with about four to five grammes of the f a t weighed (by difference from the flask con- taining it) into a flat bottoniei! flask of very thick glass. To this me add 25 C.C. of the normal alcoholic potash, close it with a good india-rubber cork, find saponify under pressure for at least an hour at a temperature of 165" F.The flask is then allowed to get perfectly cold, so that the whole soap in it solidifies. It is then washed into another ordinary flask with about 200 C.C. of water, and the alcohol having been got rid of, the acids are thrown up with a slight excesIs of seminormal sulphuric acid. The acids are collected upon a well met filter, washed with boiling water until free froin acidity, the filter always being kept full. When this point is reached the bottom of the filter is closed by a clamp, and the fat cake allowed to form. When cold, the water is run off from beneath, and the whole allowed to become air dried. The cake is removed to a tared platinum dish, and the filter and funnel, having been rinsed mit,h absolute alcohol, and the rinsings added to the dish, the whole is evaporated, dried at 212" F., aiid weighed.The soluble acids are obtained in an aliquot part of the filtmte with decinormal soda solu- tion, and, allowance having been made for the excess of seminormal sulphuric acid already added, the result ia multiplied by 00088, and expressed as butyrie acid. I iiov agree with Messrs. Angell and Hehner that with cnw m2d experieizce the loss by filter mashing of fatty acids may be reduced to a minimum, especially if any distinct globules of fat forming on the filtrate wheu cold, be carefully picked off the surface aiid added to the main cake. ITHE ANALY8T. 5 ~- - also agree with Dr. DuprQ in the statement, that, given this method of procedure, the total fatty acids of cheese should add up toabout 93.3 per cent., otherwise the analysis is not reliable and should be gone over again.The following aro the average amounts of fatty acids we have found in the under- noted cheeses, which:are slightly lower in insoluble acids than those recorded by Dr. Bell in some cases, but the results accord well with the average Hoettstorfer’s indication :- Insoluble Name. acids. Cheddar .. 87-66 Double Glo’Eter.. 87’00 Stilton . . . , 86.20 English Cream . . 90.01 Dutch ,. .. 87 20 Gruycre ,, .. 87-32 Rochefort . . 87.00 Camembert . . 8 ’7.15 Bondon . . 87-34 American } ,, 89.98 Cheddar Soluble acids . . 5-60 . , . . 6.28 .. . , 7.02 .. .. 3.26 .. . . 6.09 .. I . j.98 f . , . 6-27 . . .. 6.09 .. .. 5.95 , . .. 3-30 .. Total. 93.26 93.28 93-22 93.27 93.29 93-30 93-27 93-26 93.29 93.28 c - In deciding upon the adulteration of cheese, the limit should therefore be, in my opinion, 90 per cent.of insoluble fatty acids, but if it passes that limit markedly then *the calcdation should be made upon 88.5 per cent. The American oleomargarine cheese shows from about 90.5 to 92 per cent. The remainder of the ordinary analysis of cheese for the purposes of 8 quantitative report is then, if necessary, performed as follows :- 5. (rotnl 80&b--S grainmes of the cheese (broken up if hard) are placed in a fairly commodious tared platinum dish, and 5 c,c. of absolute alcohol having been added, the whole is allowed to soak for half an hour, and then placed to dry in the water oven till the weight is constant. This experiment is to be performed in duplicate, reserving one portion (hereafter called A) for the fat &c., and the other (hereafter called B) for the ash determination.6. Pat.-Tho residue A is treated in the dish with 50 C.C. of petroleum spirit and placed on the top of the water bath till it just boils. The whole is stirred to detach the residue, and the spirit having been decanted into the tared flask of a Soxhlet ” or other fat extractor, the now loose residue is transferred to the body of the apparatus, and the extraction conducted in the usual manner. The spirit is then distilled off from the flask and the residue dried at 212”F,, and weighed. It is here to be noted that for the purposes of cheese analysis, the petroleum spirit used must have been previously redistilled under ZOOOF.7. Acidity ccs Lactic Acid.-The residue from the fat determination is transferred from the extractor to a basin and treated with water. After steeping for some time the acidity is taken with decinormal soda, using litmus paper as an indicator (carefully avoiding any excess of the soda) and calculated to lactic acid. 8. .Lactose.-The contents of the basin are filtered through a plaited filter and washed, and the lactose is determined by FehIing’s solution gravimetrically. As previously pointedTABLE SHOWING THE AVERAGE COMPOSXTION OF CHEESE. Soluble Ash Name-of Cheese Salt Cheddar .. .. Double Glo’ster . . Stilton . . .. &ghh cream . Dutch . , .. Gruy6re .. .. Rochef ort .. Camembert .. Bondon .. .. American Cheddar .... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . o .. - Insoluble Acids 87.66 87.00 86.20 90.01 87.20 87.32 87.00 87-15 87-34 89.98 - Soluble Acids 5.60 6.28 7.02 3-26 6.09 5.98 6-21 6-09 5-95 5-30 KHO con sumed by one gramme 227-5 229.3 231.7 220-0 228.7 22s-0 229.3 229.0 228.0 220.2 Water 33.40 37-20 28.60 63-64 42.72 33-20 21.56 48-78 55.20 24-70 Fat 26-60 22.80 30-70 15.14 16.30 27-26 35.96 21.35 20.80 30.70 Lactic Acid 1 *53 1-80 1-08 -90 1-35 1-35 -72 -36 -90 -90 Lactose I I - -90 - - - trace -74 trace Insolu blc Ash 2-30 2.56 1-80 *72 2-26 3-12 1.70 -16 -52 2-16 2-00 2.00 2.22 -2 0 9.10 1.58 8-54 8.64 6.46 1.54 1-52 1.64 -75 -012 4.02 1-05 3.42 3-46 3.16 1.20TIIE ANALYST. 'I out by me when discussing the detection of cane sugar in milk (see ANALYST, vol. 5 page 31) the direct weighing of the precipitated cuprous oxide dried at 212OF. is sufficiently accurate, and better than the ordinmy volumetric method in this special case. The determination of lactoac is only necessary in the soft or cream cheeses. 9. Casein.-Is found by difference. 10. XoZzcbZe aszd InsoZubZe Ash. -The residue B is calcined at a very gentle heat until perfectly charred. It is then treated with water, filtered, and the filti-ate evaporated to dryness, gently heated and weighed. The insoluble portion is dried on the filter, strongly ignited till white, weighed, and the weight of the filter ash deducted. 11. Chlorine in Ash.-The soluble ash is dissolved in water, and the solution having heen stirred up with a pinch of calcium sulphate to remove soluble phosphates, is filtered and titrated with decinormal solution of argentic nitrate, using potassium chromate &B an indicator.

ISSN:0003-2654    

DOI:10.1039/AN8851000002

出版商:RSC    

年代:1885

数据来源: RSC

摘要:

’I TEE ANALYST. ON SKIM MILK AND ENRICHED SKIM MILK CHEESE. BY Dn. P. VIETH, F.C.S. Bead before the Xociety at the Meeting on 19th Nover,der, 1884. FOR dairies, in which not cheese-making but the manufacture of butter is the main object, the difficulty arises to dispose of the skim milk. When the milk is ‘ I set ” in order to raise the cream, and kept standing for 36 or 48 hours, or even longer, as it used to be done exclusivc!r, the skim milk obtained is, if not already curdled, certainly more or less sour, and therefore diminished in its value to some extent, whatever the way of using it up might be. But now-a-days one is enabled by employing machines in which the centrifugal force acts upon the milk to separate the latter into cream and skim milk immediately after milking, and thereby gain a skim milk which is equal to fresh milk in every respect, except its poorness of fat.Instead of, say, 3.5 or 4 per cent. of fat, as presant in fresh milk, the separated skim milk contains not more than 0.5 per cent., and in many instances less. Investigations made on the subject have shown that the fat in milk is easier digestible and more readily ftasirnilated than any other fat, and this cannot be aatoniehing con- sidering the minutely divided state of tiny globules of microscopic size, in which the fat is present in milk, not to speak of the difference in chemical composition. Skim milk therefore is not to be considered a proper food for infants, but may be taken with the greatest advantage as a wholesome drink and addition to food by hiiman beings- children and adults-with greater digestive powers, enabling them to make up for the deficiency in fat in some other way.It is, especially in large towns with their dense population, to tbe poorer part of which fresh milk is a too costly and almost unknown luxury, that skim milk ought to be made a regular article of diet. Instead of buying a quart of a watery mixture containing fermented starch sugar, alcohol, salt, and perhaps worse things besides, and called beer, two-pence would be spent much better for st quart, of wholesome, nourishing and delicious sweet skim milk.8 THE ANALYST. There are, however, objections to t’rading with skim milk, and a great deal of pre- judice must be overcome, before it would sell in an honest way to any appreciabls amount. But even if that could be brought about, only part of the skim milk pro- duced could be disposed of in this way.There are some other ways for using up skim milk, viz., rearing and fattening calves and feeding pigs, and making:skim milk cheese ; tho former will pay only under certain conditions, and skim milk cheese is not in favour with the population of this country. It was first, in America suggested and carried into pmctice, to sell the fat of milk in the best paying form of butter, and substitute it by a cheaper fat in order to make a rich cheese of poor skim milk. Two years ago I had the opportunity of analysing two speci- mens of enriched skim milk cheese manufactured in America, and published the analysis in THE ANALYST (Vol. VII., 1882, page 137).The cheeses had been made, the one with the addition of oleomargarine, the other with the addition of lard. These sub- stances cannot be introduced into the curd directly, but have first to be brought into n state similar to that in which fat is present in milk, i.e., the state of enzulsion. An American with the name of Cooley, the inventor of other dairy machinery, has brought out a centrifugal apparatus for emulsifying fat, and judging by the products I had the opportunity of examining, this apparatus does its work very well. The machine, hom- ever, is expensive, rather complicated, and requires an unproportionately great driving power, and will for these reasons moxt likely not find a very extensive application. At the Dairy Show held last year, at the Agricultural Hall, Ifdington, a very simple looking apparatus for the same purpose was shown by Messrs. Lawrence and Go., St.Mary Axe, and again this year exhibited in an improved form at the same place, and at the Bealth Exhibition, South Kensington. The apparatus is called, Lactoleofract,” and meant for making emulsions of any kind, though in the first place of those to be used in the manufacture of enriched skim iiiillr cheese. It consists chiefly of a steam injector to which two pipes, fitted with kaps, and connected with receiving vessels, are joined. The apparatus is worked as follows :-One of the receiving vessels is charged with the fat, if necessary in a melted state, the other with the liquid, with which the fat is to be emulsified. The steam injector is set to work, and the taps of the feeding pipes are opened, care being taken to run the fat in last.The steam jet breaks up the fat into minute globules, which get mixed with the liquid in a most intimate manner, and a continuous stream of a very perfect emulsion is delivered from the discharge pipe and collected; it may, however, if thought necessary, run through the apparatus over and over again. The apparatus, which is worked with a steam pressure of from 5 to 10 pounds, is very effective. A small one, looking like a toy, produces 15 gallons of emulsion, of any required per- centage of fat, per hour, and a larger apparatus 80 gallons in the same space of time. I saw an eniulsion made of 1 quart of skim milk and $-pint of meltet! oleomagarine; it was done in almost no time.A sample of this emulsion, which1 took with me, showed, when examined microscopically, the fat subdivided in a most thorough manner. When left at rest, the emulsion threw up a thick layer, which broke almost like tallow, butTHE ANALYST. 9 diffused by gently shaking the bottle, after having been kept in warin water f o r a little while. The emulsion was of the following composition :- ANALYSIS OF ExmsroN OF OLEOMARGARINE IN ~ ~ C I M & h K . Solids . . . I .. . . 28.01 per cent. Pat .. .. .. . , 21.16 ,, Solids not fat . . .. . . 6-85 ,, Tho low amount of solids not fat cannot surprise, as, of course, steam is As mentioned already, the emulsion can be made of any required degree and the water gets mixed with the emulsion. in very wide limits.condensed, of richncsie For the purpose of making enriched skim,milk cheese, the emulsion is to be mixed with the skim milk, and the mixture then treatedin the usual manner. A specimen of such a cheese, similar in shape, size, and appearance to the well-known Cheddar, was shown at this year’s Dairy Show, and a sample of it very kindly given to me. An analysis of it gave the following results :- ANALYSTS OF ENRICHED SKIN MILK CHBESE CONTAINING OLEONARGARINE. Water , , * . . . 34-47 per cent. Fat (Ether extract) . . . . 18.05 ,, Casein, etc. * * .. . . 42.96 ,, Ash 1 . * . . * . , 4.52 ,, C1. in Ash.. .. .. .. 0.61 ,, Equal to NaCl , .. . . 1.01 ,, In a larger quantity of fat, extracted with every precaution to obtain it as pure ns possible, the insoluble fatty acids were determined and found to amount to 90.78 per cent. I do not pretend to be a jtidgc on English cheeses, which, I cannot help to say, I am not very fond of. But with this reserve, 1 must declare the cheese in question of very good quality, regarding to taste, as well as to texture. I need hardly add that the determination of the insoluble fatty acids present in the fat of such a chceso gives EL ready means for detecting what it was made of. CONCLUSION OF THE PROCEEDINGS OF THE SOCIETY.

ISSN:0003-2654    

DOI:10.1039/AN8851000007

出版商:RSC    

年代:1885

数据来源: RSC

摘要:

THE ANALYST. 9 MONTHLY RECORD O F ANALYTICAL RESEARCHES INTO FOOD. I[,Y j3irqglei*'s Polytechnisches JournaZ.--Hiibl gives the following method for the mutual discrimination of fats and oils. It is based upon the fact that nearly all fats are composed of the glycerides of members of three groups of fatty acids. These are the acetic, acrylic and tctrolic acid series. The relative proportion of these acids in any given fat or oil is constar: t within certain limits, and this proportion varies only in diff went kinds of oils. The meaibers of the three groups of acids, however, exhibit a very different behaviour towaids chlorine, bromine and iodine, while under ordinwy circumstances the acids of the first series are indifferent, those of the second and third series readily- unite with definite quantit'ies of the halogens and substitution products of the first series are f nrm prl10 THE ANALYST.If, therefore, it is possible to make a fat unite with a halogen under circumstances vhich preclude the possibility of substitution, and the amount which enters into the com- pound be accuratoly determined, the number thus obtained would be a constant, and would be dependent upon the amount of unsaturated acids present in the fat. An alcoholic solution of iodine and mercuric chloride was found to give better satisfaction than iodine alone. The standard solution was prepared by dissolving 25 grams of iodine and 30 grams of mercuric chloride, each in a half litre of 95 per cent. alcohol and uniting the solutions. After standing from 6-12 hours the strength of the solution was determined by means of a standard sodium hyposulphite solution.An oil is examined by weighing out from -2 to -8 gram and dissolving in ten cubic centinietres of chloroform ; an excess of standard iodine solution is added, and after atanding from 14 to 2 hours the excess of iodine solution determined by means of the sodium hyposulphite solution. By a simple calculatim the number of grams of iodine taken up by 100 grams of fat is determined, and this number is a constant for the fat examined. The Hiibl has determined this constant for a large number of oils and fats. following are some of his results : Linseed oil Walnut oil Poppyseed oil Cottonseed oil Rapepeed oil Olive oil . Lard . Oleomargarine Palm oil . Tallow . Butter .Cocoanut oil Japanese wax . . . . . 15s. . . . . . 143. . . . . . 136. . . . . . 106- . . . . . 100. . . . . . 82.8 . . . . . 59, . . . . . 56.3 . . . . . 51.5 . . . . . 40- . . . . . 31. . . . . . 8.9 . . . . . 4.2 The method affords a ready means of determining the nature of a fat. I n case of a, mixture of two known fats or oils the proportion of each present can be readily calcu- lated. Thus let x be the per cent. of one fat and y :hat of the other, then x+yz100 ; and if nz is the iodine constant for the fat x, mid $1. that of the fat y, and if the number found for the mixture is J ; then the quantity of the fat x present in mixture is readily calmlnted from the equation loo( J-%) G Z - PI%-% For example, a commercial olive oil gave on examination 97 as the iodine constant, it was therefore adulterated with a considerable quantity of some other oil.The melting point of the free fatty acids was found to be 30". This indicated the presence of cotton- seed oil, which was confirmed by other tests. Then by substituting in the above formula, the quantity of cottonseed oil present was found to be 60 per cent. THE CIIEMICAL EXAXINATION OF PEPPER. By V? Leng. Zeitschrift fiir Anal. Cheni. 23-50 1 .-IT is well-known that the methods now in use f u r examining pepper, such as the determination of the aqueous, alcoholic and ethereal extracts, are of little real use in detect-THE ANALYST. 11 ing and estimating adulteration, it being possible by judicious admixture to produce an adulterated pepper which shall give any desired extract.The commonest adulteration is with pepper husks and palm kernel powder (palmkernmehl) ; and E. Geissler showed a short time back that it mas impossible to detect this adulteration by extraction. The determination of the alcoholic and ethereal extracts, as now practised, is therefore worthless ; and the same may be said of the extraction with petroleum-ether, proposed by A. W. Blyth. Tho author then proceeds to show that the different extraction apparatus in use give remarkably different results. Thus, Tollen’s apparatus gave a petroleum- ether extract of 4.55 per cent in 11 hours; while with Soxhlet’s only 1.98 per cent. was obtained in 12 hours. Induced by this condition of things t.he author has entered upon a series of investigations to work out a method for the purely chemical examination of pepper ; and the present paper contains an account of his first results.The method depends upon the fact that pepper is characterised, in contra-distinction to its possible adulterants by the comparatively large amount of starch it contains, and is based upon the inversion of this starch and the determination of the sugar produced. It must not, however, be forgotten that other substances besides starch are inverted by hydrochloric acid and that sugar is not the only substance that reduceszcopper solution. To obtain good results, therefore, the following directions must be exactly followed :- 3 to 4 gramsof the powder to be examined are digested for 3 to 4 hours with Q litre distilled water, (the flask being repeatedly shaken), filtered, washed with water, and the damp powder washed back into the flask, which is then filled up so as to contain 200 C.C.To this 20 C.C. of a 25 per cent. solution of hydrochloric acid iire added, and the flask is closed with a cork, through which passes a glass tube about a metre long to act as condenser. The flask and contents are then heated for exactly three hours on the water bath, with occasional shaking. The liquid having been allowed t6 cool, is filtered into a 500 C.C. flask, washed with cold water, the filtrate neutralised with sodium hydrate and diluted up to the mark. The ‘‘ reduction-value ’’ of this solution is determined with 10 C.C. Fehling’s solution diluted with 40 C.C. water. I n calculating the reducing power, 10 C.C. Fehling’s solution were taken as equal to 0.05 gram sugar. If the hot solution does not clear, a few drops of zinc chloride solution are added (as proposed by F.Mayer.) The disappearance of tho red colour with potassium ferrocyanide in a drop of the filtrate acidulated with acetic acid may be used as an indicator. The author gives the following as his mean results :- Bkacli Pepper, 52 per cent. sugar in the substance, free from ash. Thite Pepper, 60 per cent. (nearly) sugar in the substance, free from ash. Pnhe Nut Potoder, (Palmkernmehl) 22.6 per cent. sugar in the substance, PcpperZusl;~, 16.3 per cent. sugar in the substance free from ash. free from ash. No pure pepper should give less than 50 per cent. reducing sugar, calculated upon the ash-free substance. Taking 23 as the mean percentage for palm nut powder and 52 for pure pepper, the amount of the former contained in a given pepper may be calculated by subtracting tho pcrccutage of sugar found from 52 and dividing the difference by 0.29 F.H. H.THE ANALYST. ON THE DETERMINATION O F &LK FAT. B Y PRO2. DR. LIEBERXANN.-zeitSChr. fUl? Anal. Cheni. 23, 476. This is a short paper defending the author’s volumetric method for the determina- tion of milk-fat, Zeitsch. fur Anal. Chem., 22, 353, which had been called in questmion by C. H. Wolff, Pbarm. Centralhalle, 1883, p. 435, or %eitschr. fur Anal. Chem., 23, 87. The latter maintained that the method gives 0.2 per cent. more fat than that obtained gravimetrically (by evaporating to dryness on the sand-bath, and extracting with ether) ; he tried to explain the difference by assuming that milk and ether, on being mixed, undergo, like water aiici ether, a change in volume.To obviate this source of error, Wolff recommended using for the ext,raction 55 C.C. or 44 C.C. instead of 50 C.C. ether. The author, however, shows that a mixture of ether and milk undergoes no such alteration in volume as is undergono by water and ether. To test the method he wade several deterininations of milk-fat both gravimetrically, and according to his method with and without Wolff’s modification. The following is an example :- XilI&T@t. - Grmimetrically , . . , , , , . , , , , . , . . 4.220 per cent. The Author’s method Residue weighed , . , , . , , , , , 4.187 per cent. (with 50 c. c. ether) ,, determined volumetrically , , , .4.276 Wolff’s modification Residue weighed , . . . . , , . , 3.872 (with 54 c. c. ether) } ,, determined volumetrically , , , , 3‘916 As vas to be expected, the results obtained with TVolff’s method are too low. The author can only explain Wolff’s not obtaining good results with his method by assuming that he did not sufficiently dry the fat. For safe results the fat should be dried at 110Q C. for at least half an hour. As the author has slightly modified the process, he gives the following short descrip- tion. 50 e.c. milk are m-ell shaken 1x13 in a cylindrical vessel with 50 C.C. Potash (Sp. G. 1-27), and allowed to stand 5 minutes; on the lapse of this period 50 C.C. aqueous ether are added, aiid the mixture shaken moderately for 10 seconds.The operator must then give the vessel one or two vertical taps every half-minutie for 20 minutes, during which time the ether separates out clear. Of this clear ether solution 20 C.C. are drawn off with a pipette and run into aflask. Thc solution is evaporated, and the residue dried for half an hour at l l O Q or, what is still better, heated over a small gas- flame until a smell of decomposed butter is given off. The residue, after being allowed to cool in the dessicator, can either be weighed directly or determined volumetrically, according to the method described by the author in a previous communication, 22, 383, Zeitsch. fiir Anal. Chem. Soshlet’s araonietric method is recornmended for cases when the author’s cannot he conveniently used-for example, when the operation takes place in a small and badly ventilated room, whero large quantities of ethw cannot be evaporated.A drawback to its popular use is that the milk must often be submitted to two examinations, first, for normal milk, aiid, Then this does not succeed, vith the araometric method for milks poor in fat. F. H. H.THE ANALYST. 13 RAPID DETECTION OF OLEOMARGARINE.-Dr. Thomas Taylor reports to the Department of Agriculture that he has made a series of experiments with oleomargarine of different fats,. using a variety of acids to ascertain what permanent change of colour would take place by oxidation, etc. Of the various acids employed, sulphuric acid gave the most satisfactory results. I f a few drops of sulphuric acid be combined with a small quantity of pure butter, the butter mill assume first an opaque whitish-yellow colour, and, after the lapse of about ten minutes, it will change to a brick red. Oleomargarine mado of beef fat, when treated in the same manner, changes at first; to clear amber, and after the lapse of about twenty minutes, to a deep crimson. That the changes in colour do not arise from the action of the sulphuric acid on the artificial colouring matter (annatto) is certain, as I find that when annatto is combined with sulphuric acid a dark bluish-green colour is produced, entirely unlike any of the changes mentioned. Owing to the active corrosive properties of the sulphuric acid, in making these tests The test is a very simple one. a glass rod ahould be used in combining these substances.-h"cier,tiJic American.

ISSN:0003-2654    

DOI:10.1039/AN8851000009

出版商:RSC    

年代:1885

数据来源: RSC

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THE ANALYST. 13 MONTHLY RECOED OF ANALYTICAL RESEARCHES INTO DRUGS. IN the American Chemical Journal, edited by Dr. Remsen, there is a very interesting paper on "Continuous Ethorification," by L. M. Norton and C. 0. Prescott, which contains the following remarks, having a distinct bearing upon the analytical method commonly employed for the detection and estimation of ethyl alcohol in methyl alcohol, as usually performed for excise purposes :- I ( The authority for the statement that mixed ethers can be obtained by the process of -continuous etherification rests upon two experiments of Williamson. It seemed desirable to test the applic:Lbility of this process to the formation of mixed ethers anew, especially as Guthrie mas unable to repeat one of Williamson's experiments. We chose for an experiment a mixture of methyl and ethyl alcohols, containing 1 mol.of CH,OH to 1 niol. of CJ&OI€. This mixture was treated in the usual manner at 140°, and the utmost care was observed in condensing the products. A colourless distillate, free from sulphurous anhydride, was obtained, and at the same time a gas, which me were unable to condense, escaped from the apparatus. This gas possessed a strong etherial odour and mas doubtless inethyl ether, which boils at--23". The distillate resolved itself upon fractionation into three portions-one boiling from 10"-15", the second from 30"-40°, and a third portion consisting of undecomposed alcohols. We obtained from the portion boiling lowest a considerable quantity of a liquid boiling between 10" and 13O, possessing a strong etherial odour, and corresponding in every respect with the methyl-ethyl ether prepared by Williamson from sodium alcoholate and methyl iodide, and also by Wurtz, by the action of a mixture of methyl iodide and ethyl iodide upon silver oxide. The portion of the distillate boiling between 30" and 40" consisted mainly of ethyl ether. The three possible ethers appear to be formed simultaneously, but the mixed ether is formed in much the largest proportion. " The yield of the mixed ether was very good.

ISSN:0003-2654    

DOI:10.1039/AN8851000013

出版商:RSC    

年代:1885

数据来源: RSC

摘要:

14 THE ANALYST. MONTHLY RECORD O F GENERAL RESEARCHES I N ANALYTICAL CHEMISTRY. IN the BzclZetin de Zc Xocie‘te‘ ehimique de Pwis are found some researches by Zaboudsky into the exact nature of the so called residue of carbon left when iron and steel are treated by Boussingault’s method with eupric sulphate. E e finds in confirmation of the views of Schiitzenberger and Bourgeois that this is not pure carbon, but a hydrated carbon having the composition C,,H,O,. This body is insoluble in water, alcohol, ether hydrochloric and sulphuric acids, and it is impossible to convert it into pure carbon by heat alone. With nitric acid it dissolves entirely, forming a reddish brown compound having the formula C,,H,,(N0,)0,2. That it is a definite L( hydrate of combined carbon” is further proved by its behaviour with the halogens and not even decomposition by electrolysis can cause it to yield pure carbon.Upon these researches the author bases the following process for :- The detPrmination of combined carbon in iron an& steeZ.-fi’or the purpose of decomposing the iron or steel, a dry mixture of cbloride of copper and chloride of sodium is used. This mixture is obtained by evaporating to dryness a saturated solution of sulphate of copper and chloride of sodium. The metal should be finely pulverised and carefully mixed with this mixture in a mortar. Enough water should then be added to make a paste, and the mass triturated with a pestle, care being taken to keep the mortar cold. The deconiposition is effected according to the equation : 2 Cu Cl,+Fe =Fe C1, + Cu, C12.Theoretically 4.8 grams of chloride of copper, or i 4 grams of the mixture as prepared above, are required to dissolve 1, gram of iron. Practically, however, 20 grams of the mixture are found to be more convenient. After half an hour’s trituration the pasty mass is raised from the mortar and placed in a beaker, and the mortar washed with ferric chloride ( I pt. Fe,Cl, to 4 pts. water). The glass containing the pasty mass, together with the wash water, is then heated gently, and, after warming, a little hydrochloric acid is added. This operation lasts about forty-five minutes, when the residue can be collected on a filter. This is then dried and burned in the ordinary manner. The loss in weight corresponds to the weight of the hydrated carbon and is not the weight of pure carbon, as was formerly supposed.In order to obtain the true weight of the combined carbon, factors must be used. These factors represent the amount of carbon in the hydrate of carbon that has been burned. In order t o determine the mean value of these factors for the various grades of iron Zaboudsky examined a large number of specimens, and gives the following numbers as representing the amount of carbon in the combustible portion of the residue obtained by treating iron and steel in the manner given above : Pure specular cast-iron , . .. .. .. , , .720 Ferro-manganese . . .. .. a . .. . e .700 Specular manganiferous cast-iron I . .. , , .685 White cast-iron $ 0 . e .. . I ,710 Pure grey cast ironTHE ANALYST. 15 Steel (cast for guns) . , * ... .. .. ,660 Hard steel .. .. .. .. .. .. .675 Iron .. a * .. * * * . ? ( .. .690 I n the American Chenzicnl Journal is found a long paper on the determination of nitrogen in fertilizers, in which is given the results of an exhaustive series of experiments made at the agricultural experimental station, Raleigh, N.C., performed by Messrs. C. W. Dabney, Jr., and B. Ton Herff, with the view of determining the actual relation of a so-called commercial combustion (like the improved soda-lime process described by Ruffle in 1881 at the Clhemical Society) to that of the absoZute method of Dumas or one of its modifications. The Ruffle process was carried out exactly as directed by the authors, except that glass tubes were used instead of the iron ones originally described. This method has the advantage of being simpler, cheaper and somewhat quicker than the copper oxide method.Therc are fewer risks to run, fewer combustion tubes break, and for several reasons a much larger per cent. of complete analyses arc obtained by it. Oharcoal, free from nitrogen, was obtained, and the mixture with sulphur vas weighed out in 2 gram portions. I n making the combustion a noteworthy precaution is to heat the tube very slowly at first, especiallyin case of compounds containing high per cents. of nitrogen. I n some cases the determina- tion may require three hours. I f the combustion is too much hastened the results will be too low. Ordinarily, an hour and a half is necessary for making two such determinations together, the weighing and filling the tubes included.Occasionally, the final reaction in titrating is rather indistinct when this combustion had been made. The copper oxide method follovod was that described by Prof. Johnson, in which the air is removed by a Sprengel pump. It was not found necessary to pass oxygen, however, in most cases, and they, therefore, omitted the chlorate of potash from the end of the tube. In mixtures containing a good deal of horn, wherc resistant cyanogen compounds are formed, this oxygen may bc of sonio aid in completing the combustion. I n andysing compounds rich in nitrogen, and cspecially those containing much nitrate, the addition of charcoal powder to the substance causes the nitrogen to come off more regularly, and givea generally better results.For getting the air, before combustion, and the nitrogen after- wards, out of tho tube, the Authors used carbon dioxide without a pump and obtained cxcellent rcsults, though more time is consumed in this way than with a good pump, Magnesite or carbonate of manganese, put in the back end of the tube, are the best sources of carbon dioxide for this purpose. They give off their carbon dioxide slowly and uniformly. I n the Authors’ experience this method of driving the nitrogen out isfar preferable to working with a poor, or slow pump, and they recommend it to those who do not want to invest in a Sprengel punip. I f one can get a fast-working, tight pump, a combination of both plans of getting the nitrogen out is the best and quickest method. The authors expcrirnented upon four typically distinct nitrogenous bodies with the following results : - The tube used was exactly like the ordinary soda-lime combustion tube.The soda-lime and fused hyposulphite were wised by eye.THE ANALYST. Xatenal. R d e . CUO. Theory. Paranitrobenzanilid ,, ,, ., 11.495 ., 11.670 ,, 11.570 Nitrate of potash.. , . , . . . 13.735 , , 13.70 , , 13.861 Nitrosalicylic acid., . . . . . . 7.450 . , 7.655 ,, ’iqG90 Dinitrophtalyltoluidid %. . . . . . 12’620 . , 12.910 , , 12.544 They then extended their experiments to ten distinctive fertilizers, with tho sub- joined effects :-- iUatei5al. Rufle. Ammoniated cotton fertilizer , . . , 2,085 Fertilizer, with tobacco refuse , . . 2.125 Ammoniated superphosphate with 1 p. c. N from nitrate ., . . , . . . 2.110 Ammoniated superphosphate with animal and vegetable matter and nitrate . . 8.080 Shoemaker’s bonemeal , , , , . . 6.715 N. C. fish-acrap .. ,. , , .. 7.515 Cotton-seed meal, extracted , . . . 7*865 Chincha Island Peruvian, . . , . . 7-255 Shoemaker’s Ammonite €3.” . . . . 12-GS5 Dried blood , , , , , . . . 14.585 CUO. ,. 2.066 .. 2.195 .. 2.075 . I 3.095 . * 6.776 .. 7.675 .. 8.075 .. 7.270 . I 13.725 , . 14.770 Difference. I I + 0-020 .. -00.07 .. + 0.035 I, - 0.015 . . - 0.060 .. - 0.160 ,. - 0.210 .. - 0.015 ,. - 0.035 .. - 0,185 I n conclusion, they point out that these experiments, confirmed by many others in their possession, clearly show that the RuHe [and Dumas methods give equally good resulta. In general it may be said that the Ruffle process is as well suited to come aufficiently near the truth as the cupric oxide, and that in both we have two well defined absolute ” methods of estimating nitrogen in fertilizers generally.ON THE DETER31INATION O F REVERTED PHOSPHORIC ACID AND THE PHOSPHORIC ACID IN DI-CALCIVM PHOSPHATE.-BY CARL MOIIR. Zeitschr. f. Anal. Chem. 23-487. The analysis of commercial phosphates (superphosphates, &c.) has led to consider- able differences in the manure trade; and it is therefore of the utmost importance to have a mothod giving better results than the existing ones. The method practised by French and Belgian (also by many English) chemists consists in determining the phosphoric acid, solublo in ammonium citrate, by direct preci- pitation ; while, in Germany, the aqueous solution is still preferably employed.Regarding the ammonium citrate method, the author remarks that it is often likely to fail because of the difficultyin hitting off the right proportion of ammonium citrate to phosphoric acid ; further, the filtrate from the preci$,aterwith magnesia mixture, always gives a slight precipitate when treated with fuming nitric acid in excess and ammonium molybdate, and heated €or an hour at 85’ C. I t is on this latter reaction that the author has fwnded a method, which gives results agreeing satisfactorily with those obtained by the difference imthod. About five grammes of the substance are treated vith hot water in a mortar, and filtered into a 200 or 250 C.C. flask. After three successive ttreatments with hot water, the insoluble powder in the mortar and on the filter is brought into a flask and digested for an hour at 6O0-?Oo, with 25 C.C.of an alkaline solution of ammonium citrate. The solution thus obtained is filtered and added to the first filtrate, the flask containing both being then filled up to the mark. I f the liquid is not acid, it is acidulated mith a few drops of nitric acid. To 10-20 c,c. of this solution an equal volume of fuming nitric acid is added, and \then molybdate solution inTHE ANALYST. 17 excess. To ensure complete precipitation the mixture must be digested for an hour at 85" C. on the sand-bath, and allowed to cool before filtering, as the hot acid solution rapidly attacks the filter' paper. The yellow residue on the filter is dissolved in ammonia, filtered and precipitated with magnesia mixture.The precipitate can be either weighed directly or titrated with a standard uranium solution. An important advantage of this process that the direct precipitation method does not possess, is that it can be used for the examination of phosphates, manures, &c., containing magnesium compounds. The following example is taken from the author's results. The substance examined was a precipitated phosphate from Anvelais in Belgium, which had been previously analysed by two chemists, M. and G., using the direct precipitation method. Difereizce method : Total quantity '. .. Insoluble in ammonium citrate Soluble in ammonium citrate . . The Aectlaor's method : (1) ' ' .. .. .. (2) * * .. I . .. Mean .. * . .. M. obtained , .* . .. G. ,, .. .. .. Direct pi*ecipitatioia method : 31-50 per cent. 26-15 ,, 26.16 ,, 25.50 ,, 5.36 ), - 25-52 ) ) 23-55 ,, 23.552 ,: The author's results thus agreeing much better with the calculated ones than those obtained by the direct precipitation method. A NEW METHOD FOR THE QUALITATIVE SEPARATION OF TIN, ANTIMONY, AND ARSENIC,-- BY EMIL BERGLUND.% Ber. d. Deutschen Chem. Gesell, 17-95, The method is based upon the fact that the sulphides of tin, antimony, and arsenic, when boiled with oxide of copper, lose their sulphur, and are converted into the higher oxides. Thus, if tin sulphide be dissolved in sodium hydrate, and boiled with copper oxide, stannic acid is obtained. I n the samo way antimony and arsenic sulphides are converted respectively into antimonic and arsenic acids.The copper oxide required for this reaction may be prepared by precipitation with sodium carbonate, and drying at 100"-150" C. The sulphides, obtained by dissolving in ammonium sulphide, and reprecipitating with hydrochloric acid, are Tell washed, and brought info a porcelain dish, with a moderate quantity of water. The liquid is then boiled, and, while stirring, sodium sulphide carefully added (a large excess being avoided) till a completely char solution is obtained, or, at the most, only black-brown copper sulphide remains, which some- times gets dissolved by the ammonium sulphide. Neglecting this residue, copper oxide is now added, the solution being meantime kept boiling and well stirred. If sufficient oxide of copper be added, the copper sulphide sinks as a heavy powder to the bottom, leaving the supernatant liquid clear.The solution, having been thus '' desulphurized," is filtered warm. I n the filtrate are tin, antimony, and arsenic, as sodium salts of the The process is the following :-- ~ ~~~ ~- * From Zeitsch. fur Anal. Chem. 23, 573.18 T'#E ANALYST. respective acids. If much antimony be present it now shows itself by the formation of a white granular precipitate. On cooling, the liquid is mixed with one-third to a quarter its volume of alcohol ; the sodium antimonate then separates out as an extremely fine white precipitate, which, after being allowed to settle, is filtered. The filtrate must be passed several times through the filter, as there is some difficulty in getting it clear.The clear filtrate is boiled till free from alcohol, and then mixed with excess of a concentrated solution of ammonium chloride. I f a large quantity of tin be present, a milk-white precipitate is now formed. I f no precipitate be produced, there can only be, at the most, small traces of tin in the solution. I f tin and arsenic be both present, the precipi- tate contains 2Sn02, As,O,, However, whether ammonium chloride causes a precipitate or not, a few drops of ammonium hydrate are added, and sulphuretted hydrogen passed in. If a precipitate be produced, the current of H,S is continued until it redissolves, leaving, possibly, a few flakes of insoluble silica or alumina (from the porcelain dish). To the clear solution is now added one-third its volume of ammonium hydrate and magnesia mixture to precipitate the arsenic as amnionium-magnesium arseniate.If tin has not been detected in the course of the operation, the liquid, after having been allowed to stand an hour, is filtered, and the filtrate acidulated with hydrochloric acid. The direct production of a yellow precipitate shows tin, otherwise a slight white precipitate of sulphur is formed. A SUBSTITUTE FOR SODIUM CARBONATE IN THE FUSION OF SILICATES. BY Carl HoZthof.-Zeitsch. fur Anal. Chem. 23-499. THE Author has for many years used sodium bicarbonate instead of the monocarbonate, or a mixture of the carbonates of sodium and potassium as a flux. I t possesses several advantages; it can easily be obtained pure, allows of being finely powdered, is not hygroscopic, and when slowly heated gives off its water of crystallisation, and the second GO, molecule without decrepitation. The fusion takes place easier than with the mono- carbonate, in most cases below the melting point of the mass, the evolution of the car- bonic acid causing the acids to exchange bases sooner than they otherwise would. The Author proceeds thus :-Pure, dry, and finely powdered sodium bicarbonate, from 12 to 15 times the weight of the silicatepnder examination, is used. A quarter of the weight is placed directly in the crucible, a second quarter intimately mixed with the powdered substance in a warm dish, and this, after mixing with another quarter on glazed paper, is filled into the crucible, the remaining quarter being used to wash the dish and paper. The crucible, which may be quite half full, is first heated carefully over a moderate flame for a quarter of an hour ; the heat is then nlowly increased during the next quarter of an hour till the lower half of the crucible is just red. Finally, the heat ia raised until the mass melts and becomes clear ; the fusion is then complete. F. H. H,

ISSN:0003-2654    

DOI:10.1039/AN8851000014

出版商:RSC    

年代:1885

数据来源: RSC

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THE ANALYST. 19 REVIEW. ORGANIC CHEMISTRY. By E. Frankland, Ph.B., F.R.S., Pc., Professor of Chemistry in the Normal School of Science, and Francis R. Japp, N.A., Ph.D., &G., assistant Professor of Chemistry. London : J. & A. Churchill. N the preface the Authors say :-‘l The lecture notes for chemical students, already published by one of us, and now in their third edition, were always intended to be the precursors of text books on Mineral and Organic Chemistry. The present volume fulfils intention so far as Inorganic Chemistry is concerned. It is constructed on those orinciples of classification, nomenclature, and notation, which, after an experience of nearly twenty years, have been found to lead most readily to the acquisition of a sound and accurate knowledge of elementary chemistry.” Now had the authors introduced the saving phrase in our opinion )’ after L‘ have been found ’) then we would not have had anything to say.We have no wish to fight over again the battle for and against graphic structural formulm, but we feel bound to protest mildly on behalf of other teachers who have also had a similar experience, to the implied conclusion that any system having for its basis the excessive use of such formulm is admitted by all to lead most readily to the acquisition of a sound and accurate knowledge of elementary chemistry. Every author of a book is entitled to his opinion, and to have that opinion respected so long as he clearly puts it forward simply as his own, but the moment he claims universal acceptance for it, he excites criticism and contradiction.Such criticism and contradition mill not however come from us on the present occasion, because we do not wish to allow our disagreement with some of the notation to warp our ideas of the book as a whole. Before leaving the subject we would simply take by chance the for- mula of dipotassic tetratellurite which heads page 313, viz. :- ’ 0 0 0 0 II II It II K-0--Te-0-Te-0-Te-0-Te-0-K as a specimen of the kind of formula likely to lead (‘ inost readiZy ’) to the acquisition of elementary chemistry and against that to place the words of warning recently spoken by Dr. Remsen, in his able work on theoretical chemistry, to the effect that we are now in a period of formula worship, and the great danger is, lest in the estimation of students more value be attached to the construction of a formula, than to a really practical know- ledge of the nature and properties of the substance represented.Having thus made our protest, we now proceed to examine the general merits of the work, and happily here we are quite in accord with the authors, because after a most careful perusal of the book, we have formed a very high estimate of its general excellence. It opens with a series of 20 chapters (occupying 130 pages), entirely devoted to the theories of chemistry ; and in this portion, the most modern ideas are introduced, and the relations of the various recent researches in chemical physics, to the e!uc.clation of modern chemical theories, are carefully and individually explained. Then follow the non-metals, and the metals in the order usual in text books :-the descriptions of the more important compounds being printed in ordinary type, and the rarer ones in small type.This might be objected to by some purists as aavouring of cramming, but20 TRE ANALYBT. it is, after all really, in our opinion, a legitimate assistance to the‘student, and, had it no’ been done, the work woulcl have been of a Rize altogether too unwieldy for comfortable reading. Besides the excessive use of structural fornlule, there is another part of the book that might have also been modified, and that is the lengthy remarks upon potable water. Here again me meet with another of the points upon which all the chemical world does not absolutely agree with the senior author, and we have no inten- tion of treading upon his toes when me say, that, out of a work of about 640 pages of descriptive chemistry, 26 pages are too much to devote to the single subject of potable water.‘This is the more marked, because no single instruction as to the practical analysis of water is attempted, and indeed we are told (page 546), that the proper chemical examination of a sample of water ‘ I requires veelrs, sometimes even nionthsj for its completion.” Thus the whole of these 26 pagea are simply devoted to a sort of expositioii of Dr. l?rankland’s views upon water, and the cteductions to be dra-n-n by those using his organic carbon czncl nitrogen process. We submit that this section would have much more appropriately formed the nucleus of a special work, than being as it is, placed in a general manual in conjunction with the metal calcium, We E L ~ O not to be taken as dissenting altogether from the matter of this section, which is in many respects very sound and ably written, but we look rqmn it as the Professor did on dust, viz., as an excess of matter in the wrong place.Taking the whole work, however, it is, as me have before said, a most excellent one! nncl likely to be of great service to students of general inorganic chemistry. MONTHLY RECORD OF ADVANCES I N T€IX PREPARATION O F FOOD 0’33 DRUGS. ’ lodizecl Cod-Liver OiL-While abstracting Hubl’s paper on the absorption of iodine by oils, we received from Messrs. Walker and Moore a sample of cod-liver oil treated in a similar manner for medicinal. purposes. It is considered by some authorities that the small, but variable, amount of iocline found naturally in this oil is an important factor in its tharapentical action, a n d the idea of the originators of the article under reriew, is to present a11 oil always containing a definite amount of that element.On analysis, the sample submitted proved to be iodized to the extent of -25 per cent, The oil also answered the tests for genuine cod-liver oil, and me have no doubt that it will find favour with those Physicians who desire to be always able to prescribe an article of definite composition in preference to running the ordinary commercial chances of both strength and purity. Report (Seventh Annual) of the Board of Health of the State of New Jersey ; Sanitmy Control of the Food Supply, by W. K. Newton, N.D. ; Some Facts about the New Jersey Milk Adulteration Act, by Tv. 41. Newton, M.D. ; American Chemical Review ; American Grocer ; British Medical Journal ; The Chemist and Druggist ; The Country Brewers’ Gazette ; The Comkeeper and Dairyman’s Journal ; The Grocer, The Grocers’ Gazette ; Independent Journal ; Invention and Inventors’ Mart ; The Lancet ; Le Mouvement Hygienique ; The Nedical Record ; The Medical Press ; The Miller ; The Nonthly Magazine of Pharmacy and Chemistry ; The Phar1naceutic:J Journal , The Polyclinic ; Sari Francisco News Letter ; Science ; Scientific American ; The Stndents’ Journal. BOOKS, &a, RECEIVED. NOTICE TO CONTRIBUTORS. All Letters and 1f.S.S. intended for the literary part of this Journal should be addressed t o the Editoyinl Department, 325, Kennington Road, London, B.B,

ISSN:0003-2654    

DOI:10.1039/AN8851000019

出版商:RSC    

年代:1885

数据来源: RSC