摘要:

THE ANALYST. NOVEMBER, 1889. ON THE ESTIMATION OF SULPHUR I N PYRITES. BY G . LUNGE.* IT is a well-known fact that the estimation of sulphuric acid as barium sulphate, is not quite accurate when the solution contains iron salts. Although the precipitate is always distinctly coloured by iron, the results are, however, slightly too low. The reason of this peculiar fact has been completely cleared up by the investigation of Jannasch and Richards ; it is caused by the formation of an insoluble barium-iron sulphate. These analysts, therefore, condemn in their paper my process for the estimation of sulphur in pyrites as being inaccurate, but they do not mention that this can only refer to an old process of mine, published in my work on the soda industry, as already in 1881 I advised to first precipitate the iron with ammonia.I now hear that Jannasch finds this to be a perfectly reliable method. Looking at the immense importance of the process (every year perhaps a million tons of the article are sold on analytical certificates), I had already commenced a thorough investigation, SO as to make everything perfectly clear. Let us first see, however, how matters stood before Jannasch’s and Richards’ investigation. In my work on soda manufacturing, I have preferred to recommend the treatment of the pyrites with aqua regia, instead of the fusion with nitrate and carbonate of soda. * Zeitschv. f. angew Chemie, No. 17, 89.205 THE ANALYST. Fresenius, ~ h o made his assistants perform a number of analyses, however, showed t h dry process to give better results, on account of the complete isolation of the iron.One of his assistants got even 1 per cent. of sulphur too low, which was attributed to the solvent action of the ferric chloride on tha barium sulphate. Now I found in 1881, first, that the presence of iron, as ferric chloride, renders the precipitation with barium chloride somewhat inaccurate, as the barium sulphate is always ferruginous, and can only be freed from iron by using large quantities of hydro- chloric acid, which causes a loss of about -5 per cent. of barium sulphnte. In two analyses the percentage of sulphur was found to be from 46.7 to 47.32 per cent. ; average 46.98 per cent. I further proved that perfectly concordant and accurate results may be obtained by precipitating the iron with the smallest possible amount of ammonia, and washing the precipitate on a filter with boiling water.I n all my experiments I tested for sulphuric acid in the ferric hydrate, by fusing with soda, and dissolving the mass in water, etc., but I have never found a trace of it, so it is a needless operation, Then I showed that the second method gives a little more sulphur than the first, but after all, only about + *18 per cent. Elow they managed to get as much as 1 per cent. difference in Fresenius’ laboratory, I. think I can explain by their pyrites con- taining traces of galena, heavy spar, or even gypsum. I n some experiments by Jannasch and Richards, there could be no question of galena or heavy spar, but, as they observed, a prolonged ignition of the precipitate may cause volstilisation of some of the sulphate, and any increase in weight through presence of iron be more than counteracted through this loss.The problem to find a reliable process for sulphur estimation by a wet process, was sufficiently solved by my labours. The process has been generally introduced in Germany and England, and is the only accepted process in the German soda trade, and the many complaints, of analysts differing in their results (by using the older process), have gradually died out. I now wish to show that Jannasch’s and Richards’ objections only relate to my first published method. They describe twenty-five different experiments, which all again prove the already known fact that in presence of iron the estimation of sulphur as barium sulphate is incorrect. Their last experiment also puaZitativeZy shows the formerly not known cause of this error, viz., the formation of an insoluble barium-iron sulphate, which, on ignition, slowly but gradually loses the part of the sulphuric anhydride which may be supposed to be in combination with the iron..They say : The experiment (heating the precipitate a t a bright-red heat) can be continued for half an hour without getting rid of the fumes of sulphuric anhydride, and the precipitate is constantly increasing in colour. Whilst they got from 10 C.C. of their normal acid 1*1608 gram. barium sulphate in absence of iron, when this mas added they got an average of only 1.117, or about 4 per cent. too little. These remarkably large differences, which far exceed those got by Fresenius, no doubt were caused by the unusual and continued ignition.However, their experiments once more conclusively show that the estimation of the sulphur in presence of iron is not reliable, and regularly gives results too low, although the loss must vary according to circumstances. But this does not occur when the iron is first removed by mems of ammonia, which process is, however, not mentioned in any of their twenty- five experiments. True, they casually mention that the previous precipitation of the -THE ANALYST. 203 iron by ammonia is inadmissible, sincs even after a double precipitation the precipitate still retains * 5 per cent of sulphuric acid (as basic ferric sulphate). They do not, how - ever, seem t o have made any accurate experiments themselves.We will also presently see that it really depends on how the precipitation is performed, and that if sufficient care is not taken, even a far greater quantitythan -5 per cent. will be retained by the precipitate, But, as already mentioned, I took care not to commit any errors, and have convinced myself of the absolute absence of sulphuric acid from the precipitate. Now all this ought to be a sufficient answer to those who think my process inaccuratc, but the matter being of such vast analytical importance, I resolved to again investigate the matter from beginning to end. As, however, my many professional duties prevented me from doing the analyses myself, I have had them performed by two gentlemen in whose abilities I place the greatest confidence, and who have investigated the matter quite independently of each other.Ch. Barbezat prepared (as I did in 1881) a solution which represented an iron pjritis, viz., contained 2 molecules of sulphuric acid for 1 atom of iron. The solution was not only pipetted 0% but also weighed. The liquids were precipitated by ammonia, the ferric hydrate washed with boiling water, and, after drying, fused on the blow-pipe with soda. After dissolving in water and filtering, hydrochloric acid and barium chloride was added, and the fluid allowed to stand a long time. Now a remarkable fact was disclosed. I n his first two experiments, Barbezat brought the iron sulphate solution to boiling heat, added ammonia till it had a faint smell, boiled until smell had disappeared, and then collected and washed on to a filter, until the filtrate measured nearly 700 C.C.The dried precipitate gave, after fusion with soda, a very distinct .reaction for sulphuric acid, which, when weighed, amounted to 3.6 per cent. of the total, or a still larger error than got by Jannasch and Richards, who only found -6 per cent. Now, in my description of the process, I have particularly laid stress on using a moderate excess of ammonia. I said : *‘ The moderate hot fluid is’ mixed with a not too large excess of ammonia, filtered off after about ten minutes, and washed on the filter with boiling water until the filtrate gives no longer a cloud with barium chloride, even aftor some time.” His attention being called to this, Barbezat repeated the experiments, and now found in three cases not a trace, and in another case only the merest sign of sulphuric acid, and this trace was most likely caused by absorption of sulphurous vapour during the fusion.H e worked with iron pyritis itself, which he had obtained from Spain, and which was free from copper, lead, and other sulphides. From the finely agated sample, 1 gramme was taken for analysis. Experiments were made (a) with my old process, without separa- tion of iron; ( b ) with my modified process of lSSl ; ( c ) with Fresenius’ process, the fusion with soda and nitre. ( a ) and ( b ) were heated exactly according to my directions with aqua regia, consisting of one part of fuming hydrochloric acid and three parts of nitric acid of 1-4 sp. gr., both, of course, free from sulphate.The evaporation on tho water-bath takes about fifteen minutes, and no free sulphur separates. When dry, the mass is treated twice with excess of bydrochloric acid, and again evaporated. 100 C.C. The experiments conducted by Anast Obregia are more to the point.204 THE ANALYST. of water and four drops of hydrochloric acid are then added, and the liquid filtered froin any gangue. The boiling fluid was directly mixed with barium chloride, and after standing for about forty-five minutes, the precipitate was first washed by decantation, and finally washed on the filter with boiling water. The washings did not get turbid on standing, and the ignited precipitates were all crimson-red. The filtrate, measuring about 100 c.c., was slightly warmed and mixed with ammonia, until it acquired a strong colour.After ten minutes the precipitate was washed on a filter with boiling water, until the filtrategave not the slightest cloud with barium chloride. NOW, Obregia exactly carried out my plan : to choose a rather large funnel, which is so made that the filter exactly fits it, and the filtrate constantly fills its stem. The water must be really boiling, and squirted into the centre of the ferric hydrate so as to get a thin paste, and prevent formation of channels. Working in this way, both ferric and aluminic hydrates may be conveniently washed on a filter, without the troublesome decantation, Obregia found the washing to last from three-quarters to one and a-half hour, according to the quality of the filter-paper. The total volume of the filtrate seldom exceeded 250 c.c., so that there was generally no need for concentration before estimating the sulphuric acid.The ferric precipitates were now each time dried and fused in a platinum crucible with perfectly pure soda. The fusion was carried out by placing the crucible in a per- forated sheet of asbestos, and heating with a Bunsen burner. This simple arrangement prevents the access of sulphury vapours, and renders unnecessary the use of a Berzelius lamp, as used in Jannasch’s and Richards’ experiments. The mass was now exhausted with water and tested as usual for a sulphate. Even after standing for twelve hours, not a trace of it could be detected. If, therefore, one only works according to my directions, the ferric oxide will be perfectly free from sulphur.The precipitation of the iron free liquid was done with barium chloride as usual. The barium sulphate, after being ignited, was always perfectly white. The ore was fused with ten times its weight of a mixture of two parts of soda and one part of nitre, in a platinum crucible placed in asbestos, with all the precautions recommended by Fresenius, It must, how- ever, be observed, that this method requires more manipulating skill, and takes a t least double the time of the aqua regia process, and that it also quickly spoils the crucibles, The following percentages of sulphur were obtained :- Three experiments (a) were performed. Five experiments ( b ) were made. Three experiments ( c ) were carried out. A B C Lunge’s old Lunge’s method, Fresenius’s method.1881. met hod. 52.38 52.70 52.46 52.38 52.14 52.49 51.94 52.22 52.3 1 52.26 52.39 Average 52-23 52.40 52.42THE ANALYST. 205 From these results I now can, with the greatest of certainty, draw the following con- clusions :- 1. My process of 18S1, viz., the acid treatment of the pyrites, and removal of the iron by ammonia, before precipitating the sulphate, gives completely concordant results with the fusion process of Fresenius. Even when the first experiment (B) is rejected, the average still c3mes to 52.32 per cent., therefore differing only -10 per cent. from Fresenius’ figures, who, in his own laboratory, with his own process, got far greater differences, viz., from 43.74-44.04 per cent. so .3 per cent. 2. By these proved facts, also by the direct testing of the ferric precipitates, it is shown that when working properly, no sulphuric acid is retained.I n this view I am supported by Barbezat and Obregia. 3. The former opinion of Jannasch and Richards, that my process ought to be rejected from a purely scientific point of view, does not relate to my process of 1881. This process is, a t least, quite as accurat,e as the one of Fresenius, but has, besides, the advanta,ge of being performed in much less time (not without advantage to works- chemists), and many analyses can be carried on a t once. It further saves the wear and tear of the platinum crucibles; and last, not least, it is applicable in cases when the ore contains heavy spar, which renders Fresenius’ process unreliable. Therefore my process of 1881, on account of its easy execution and reliability, deserves the preference over others, in the estimation of sulphur in pyrites. 4. My older process, which does not provide for removal of the iron, gives, as I found in 1881, results which are too low, but only by -17 or -19 per cent. I n 1889 I found it t o be *18 per cent. Jannasch and Richards got far greater differences, but this is most likely caused by their extraordinary system of prolonged and intense ignition, such as nobody would think of doing. The process may, therefore, be trusted to yield results quite accurate enough for technical purposes, but in more important cases of buying and selling large quantities, my new process is to be preferred.

ISSN:0003-2654    

DOI:10.1039/AN889140201b

出版商:RSC    

年代:1889

数据来源: RSC

摘要:

THE ANALYST. 205 ANALYSIS OF WATER FOR DOMESTIC PURPOSES.* BY FERD. FISCHER.? THERE is scarcely a branch of analytical chemistry where exist SO many different views as in water analysis. Since analyses of potable waters are mostly done by professional analysts, instead of medical men, the chemical work has certainly become more exact ; but the conclusions drawn from it are still, in many cases, incorrect, and do not rest upon sound foundation. Since Koch’s discovery of the cholera baccillus, many medical men have taken to the bacteriological method, which in itself is very praiseworthy, if not too exaggerated conclusions are at once drawn. Plagge and Proskauer are of opinion that the chemical composition of a water goes for nothing ; all they require * Slightly abridged from the original.t Z&schr. f. artgew C7~emrie, No. 18, 1889.206 THE ANALYST. being freedom from infecting matter, but they do also confess that this matter can but seldom by proved by the bacteriological research. 0 ther chemists, although not objecting to a chemical analysis, will not form any opinion without a bacteriological investigation. A normal water, according to Koch, is such a one [which contains in one c.c., less than 300 germs. Plagge and Proskauer, however, do not allow more than 50 or 150 a t the most, which latter number is the one fixed by the Swiss Society of Analytical Chemists. A. PfeifFer, however, condemns a water, when it gives the figures 1000; If the counting of germs really sufficed to judge a water by, a chemical analysis would be superfluous, and any intelligent person might readily learn water analysis by attending a fortnight’s course of cramming in some hygienic institution.On the spread of infectious diseases by means of drinking water, the medical profession has not yet quite agreed. Whilst Koch and his adherents have found the cholera baccillus in an Indian tank, and have proved the spread of cholera through the use of that water, their statement is still doubted by Pettenkofer and his school. According to Emmerich and Trillish, a sure detection of the typhoid baccilli in water is as yet im- possible, and it is not at all proved that the cholera vibrioni, noticed by Koch, are really the actual source of cholera in human beings. C. Cramer, in his paper on the water supply of Zurich, isof opinion that it is as yet impossible to find the typhoid germ when it has left the human body, and it must also be considered the baccilli often completely disappear.The Zurich commission appointed to investigate the matter, unanimously rejected the bacteriological process. Under such circumstances, it sounds strange to demand a water to be especially free from infecting matter when this cannot be proved. But even if this were possible, i t is certainly as yet quite undecided, whether the baccilli generally occurring in water are not quite as harmless as the many millions which a person swallows during a day, in the shape of sour milk, cheese, etc. The value of the germ-counting process becomes still more doubtful, as it is influenced by numerous circumstances.Wollffhiigel and Riedel pretend that even the motion of the water is of influence on the germ number, and that it is also influenced by the temperature. One sample, when freshly taken, stood the test all right ; but after it had been kept for a short time in a room it was proved to be dangerous to life. It must also be considered, that some pathogenic bacteria in water are stunted in their growth by the presence of masses of other unpretending bacteria. According to Piefke the purification of water in filters is actually caused by bacteria. The presence of the harmless bacteria is, therefore, even a good sign, and shows the fallacy of the germ-counting process. I n judging a water for domestic purposes, one has to decide whether or not it is free from human or animal excrements. It is, however, rare to actually find such matter, as they very rapidly decompose into other bodies of doubtful chemical composition, and under the influence of oxygen soon yield carbonic acid, ammonia and nitrous or nitric acids. The decomposition goes quickest in rapid waters, and more quickly still in porous soils.I f an analyst has now to give an opinion on a spring water he must get information about the nature of the soil, Most soils will retain phosphates, potash, ammonia and nitrogenous bodies, whilst chlorides and nitrates, also sulphates, are kept in solution. I f the soil Chlorides in particular point strongly to the presence of urine.THE ANALYST. 207 has lost its absorbing power and the oxygen supply is insufficient, the water will show nitrites, ammonia, and decomposing organic matter.Therefore, unless the nature of the Foil is known, no safe conclusious can be drawn from the components of a sample of water. To judge of the quality of a water intended for domestic purposes one has to look, therefore, for such bodies as are connected with human or animal excrements, viz., decomposing organic matter, ammonia, nitrous acid, nitric acid, and chlorine. It is of little use to estimate anything else. I t has been proposed by Schulze, AlmBn, and also by Reichart, to fix certain standards or limits t o be used by every analyst. I have already demonstrated that those limits were far too exacting, and, for instance, did not suit the town of Hanover. It will be seen from the table the numbers proposed by Tieman and Gartner and the Swiss Society are very close, whilst the International Congress at Brussels proposed figures which cannot be accepted.The English Commission, 1868, attached most importance to the organic matters. The thoughtless application of these figures must give rise t o the greatest confusion, but they are certainly not without any value at all, as when they exceed the limit, a water may be regarded as suspicious. Nobody has, however, a right to declare a water dangerous to health, or advise a well to be closed on the mere strength of a chemical, and less still a microscopical, analysis of a sample, unless the well and its surroundings have been thoroughly inspected. TABLE SHOWING THE LIMITS OF IMPURITY AS PROPOSED BY VARIOUS AUTHORITIES (Translated into grains per gallon). Grains per Gallon. Organic matter as K,M,O, including Org. Carbon ,, Nitro- gen.. * . Albumenoid Ammonia .. Ammonia . . Nitrous Acid. . Nitric Acid . . Chlorine . . Sulphuric Anhy- dride . . Residue . . Hardness . . d is“ g a00 -- 4.2-7.0 - - - 0 0 3.5-10.5 1 *40-2.10 5.60-70 35.0 12.6-14.0 *70 - - *0035 -0014 0 1.40 1-40 - 35.0 -

ISSN:0003-2654    

DOI:10.1039/AN8891400205

出版商:RSC    

年代:1889

数据来源: RSC

摘要:

- 208 THE ANALYST. ESTIMATION OF EXTRACTIVE AND SPECIFIC GRAVITIES OF OFFICIAL TINCTURES. BY J. SPILSBURY, F.C.S., Phaynz. ch. THE following summary of averages is based on estimations extending over a period of ten years. The tinctures from which the samples were taken having been manufactured, under my personal supervision, from fine specimens o$ crude drugs (not specially selected samples) and strictly in conformity with the formula of the British Pharmacopceia. The evaporations were conducted in thin porcelain basins of about 2 3 ins. in diameter, with the exception of some rectified tinctures which had a tendency $0 creep over the sides, in which cases glass beakers of about 2 oz. capacity were substituted. The respec- tive residues were exposed on the water-bath to a temperature of 21 20 Fah.and weighed at the expiration of two hours : Extractive from 10 C.C. expressed in grammes. Tincture of Aconite . . .231 Aloes . . .588 Arnica . . -029 Asafetida *643 Orange . . *335 Orange from fresh fruit -256 Belladonna *083 Benzoin . . 1.526 Buchu . . *179 Calumba . . -094 Indian Hemp -430 Capsicum.. a080 Cardamoms -5 67 Cascarilla . . -100 Catechu . . 1.068 Chiretta . . -118 Cimicifuga -208 Cinchona . . *470 Cinchona (compound) -439 Cinnamon -1 40 Colchicum -1 00 Hemlock . . ~ 2 4 3 Cubebs , . ,118 Digitalis . . -407 Ergot . . *ZOO Galls .,. 1215 Gelseminum 1 18 Gentian . . *398 Guaiacum 1 *3 9 2 Henbane .. *299 Specific Gravity at 60° Fah. *855 ~ 9 6 1 a842 *865 -935 -894 -926 -889 *939 ,928 -846 -s43 *944 ~ 9 3 2 ~961 -927 -929 -939 *937 -928 0926 -942 -846 -939 *932 *978 -929 -939 -939 -930 Extractive Specific from 10 C.C.Gravity expressed at in grammes. GOo Yah. Tincture of Jaborandi. . .232 Jalap . . -355 Rhatany . . -314 Larch . . -128 Lobelia . . ~ 3 0 1 Lobelia (Ethereal) -105 Hop .. -267 Myrrh . . *366 Nux Vomica -122 Opium (simple) -4 16 Pyrethrum -153 Quassia . . -002 Quinine . . -532 Rhubarb . . 0538 Savin . . -235 Sqiiill . . -878 Senega . . 0318 Senna . . -835 Serpentary -087 Stramonium so45 Surnbul .. *365 Tolu . . 1.223 Valerian . . *208 Valerian (Ammon- iated) . . ,237 Vera trium * 189 Ginger (strong) 01 9 7 -928 *940 -937 -846 -939 -824 ,930 -849 -888 -936 *860 -92 1 '939 -955 9 3 3 ,953 -93 1 -893 -91 1 *939 -931 a880 *928 0907 -847 9 4 7 The inference deducted in obtaining the foregoing resnlts indicates that tinctures manufactured under similar conditions should not vary from the average amount of extractive in the proportion of more than *01 gramme for every -5 gramme yielded, 10 C.C. of Tincture being used for the evaporation.

ISSN:0003-2654    

DOI:10.1039/AN8891400208

出版商:RSC    

年代:1889

数据来源: RSC

摘要:

THE ANALYST. 209 NILK ANALYSIS. BY DR. BENNETT F. DAVENPORT.* IN the discussion of the relative merits of the different methods of milk analysis which was published in the June number of THE ANALYST, the many advantages of a simple modification of Wanklyn’s method does not, I think, receive its due consideration. This modification, which I have adopted, I have already published in my Annual Report as Milk Inspector for the City of Boston, Mass., 1885, and as Analyst to the Massachusetts State Board of Health in their Annual Report for 1886, page 138. As being now the method generally followed by most of the official milk analysts in New England, a simple description of it may be of interest t o others. The 5 grms. of milk are weighed off in a large flat-bottom platinum capsule of full Z$ inches diameter on the bottom, and about 3 inches across the top.The $-inch high side turns up from the bottom, not with a sharp angle, but slight rounding, this being about the curve with which the milk runs up the rim of the capsule drawn by capillarity. The milk in drying down does not thus form any thicker deposit a t the angle of the side than elsewhere upon the about 5 square inches of bottom surface of the capsule. This relatively large amount of surface, one square inch to each grm. of sample taken, causes each inch to be covered with only a little over a single grain of dried milk solids. The deposit is therefore so very thin as to be readily exhausted of its fat in its subsequent treatment with boiling petroleum naphtha. When using such small dishes as were originally proposed by Wanklyn, the residue would be so thick, that is about three times, as would naturally render any such rapid method of extraction as I employ impossible, as the English analysts have learned.Each capsule has its serial number engraved upon it, and they are made to weigh a little over 25 grms. each, that the bottoms may be stiff enough to remain perfectly flat-a matter of very great importance. They are also made to differ from each other only in the second and third places of decimals, so that only those weights have to be changed in many weighings, which is a matter of no little saving of labour where many score of weighings are to be made each day. A table of their weights is kept within the case of the scales. These capsules, containing their samples, are placed upon a constant-level closed-top water-bath, of the peculiar construction described on page 269 of the Journal of Analytical Chemistry.Here, being surrounded by atmosphere not already nearly saturated with moisture, as would be the case if they were upon a water-bath with openings on its top, they quickly evaporate to apparent dryness, They are then transferred €or their final drying t o a constant weight to one of Weis- negg’s large porcelain-lined air-baths, regulated to the constant temperature of 105O C. Here they are dried in about half an hour, when they are cooled in a desiccator and each weighed immediately upon being taken out, to guard against their rapid gain in weight from exposure to the air. Replaced upon the closed-top water-bath, the capsule is filled from a wash bottle with petroleum naphtha, of the quality of the benzine of the U.S. Pharmacoposia, revision of 1880. This, unlike ether, will dissolve out neither milk-sugar nor lactic acid from the dried milk-solid residue. Moreover, one gallon of it costs but as much as one pint of ether would, which is a matter of some little con- This will hold twenty-five capsules a t a time. * Jowrnal of Analytical Chemistvy.210 THE ANALYST. sequence to one like me, who has had to use about 100 gallons of it in milk analyses during the past five years. The naphtha in the capsule, after being allowed to boil down about one-half, is decanted off against a rod into a basin to guard against the remote possibility of some flakes of milk residue being poured off with it.Replaced upon the bath, the capsule is refilled with naphtha. This boiling up and decanting off is repeated three to four times, when after the last one the outside of the capsule is washed off with naphtha played upon it from the wash-bottle, to prevent any residue of fat being left there. The capsule, then finally replaced upon the bath to dry off the naphtha, is then cooled and weighed as before, the butter being rather determined from the loss of weight in the solids than by the weight of the evaporated washings. The ash is made by ignition of the capsule over a one-inch wide Bunsen lamp, which thus gives so wide a flame as not to require a heating to a high temperature a t one point, and thus a possible loss by the volatilisation of the potassium chloride.The milk-sugar I determine by the use of a Soleil-Ventzke saccharimeter, in the same manner as has now been several times described in the journals by Drs. Wiley, Vieth, and others. The other ingredients which reduce copper in Fehling’s solution, are not thus reckoned as sugar, by which the apparent amount of albuminoids present, which are obtained by difference, would be diminished. The peculiarities of my modification is then the use of an evaporating capsule of such a very large relative area as will leave the residue thin enough to be readily exhausted by the boiling naphtha. Thus a diameter of Z j inches in the capsule will do for 5 grms. of better than average quality of milk, with a surety that there will not be as much as one-tenth of 1 per cent. of fat left as a maximum error. And surely this is fine enough for all commercial work, and it is much t o be doubted if much which affects to be more accurate by a decimal than this is really so. The method, as involving no transfer of substance, cannot well be made more simple for the determination of total solids, fat and ash. When the average life of such an evaporating capsule under reasonable usage is considered, it cannot well be cheapened, although the outlay for a kilo. of platinum for forty capsules like mine does, it is true,involve an original expense of nearly 400 dollars. The shape of my capsules makes possible completeness of ex- traction with the solvent used, and the construction of the closed water-bath hastens the process in no small degree.

ISSN:0003-2654    

DOI:10.1039/AN8891400209

出版商:RSC    

年代:1889

数据来源: RSC

摘要:

210 THE ANALYST. ON SOME RESULTS OF ANALYSES OF OLIVE OIL FROM DIFFERENT SOURCES. BY LEONARD ARCHBUTT.* THE examination st various times during the past seven or eight years of samples taken from large bulks of olive oil intended for lubricating has afforded an opportunity of making a comparison of the oil from several different sources ; but as, unfortunately, only a fraction of the samples have been labelled with the port of shipment, the number available for purposes of comparison is not so large as it might have been. The results are arranged in the following table, and the following conclusions may be drawn from them :- * Journal of the Society of Chemical hdl6stry.THE ANALYST. 21 1 Total Numberof Samples. Source of the Oils Number Examined for Number Per Cent. Free Fatty Acid (='Ieic Acid)* Adulteration found found as well as for Genuine. Genuine.I Acidity. Highest. Seville . . .. Malaga .. Unknown .. 32 35 3 Spain (total), , 32 31 96.8 10.0 35 27 77.1 25.1 3 2 66.6 5.6 Gallipoli . . Monopoli , , Gioja . . .. Naples . . .. 1.5 2.0 2.1 1.5 -9 4.1 4.1 9.2 Italy (total) . . 4.4 6.7 3.3 5.5 7.3 10.9 6.3 9.3 -_1-- Sicily (Messina) 36 28 2 12 3 Greece (Zante) . . Candia . . . . Levant. . .. ---- ---- 30 29 96.7 25.2 22 9 40.9 16.6 2 2 100.0 8.7 10 6 60.0 16.8 3 * . .. 13.5 -__------ - - ~ - - 4.6 5.5 8.5 6.7 9.5 10.4 -- I-- I I-- 1 2 8 3 100-0 1 Lowest. 1 Average. The Seville oils, both as regards their freedom from acidity, and the high percen- tage of genuine samples among them, prove to be superior to the famed Gallipoli oils. The acidity of some of the samples of Malagn oil was very high, but the average acidity was less than that of any of the Italian oils, except those from Monopoli, of which only three samples were examined.Among the Malaga oils there was a large percentage of adulterated samples. Taking the Spanish oils generally, although they appear from these results to be more liable than the Italian oils to be adulterated, yet, on the other hand, they are as a rule decidedly more neutral, which, as regards lubrication and burning, is a very important point. Amongst the Italian oils those from Gioja are distinguished for their acidity. The small number of adulterated Italian oils is worthy of note. My analyses of the oils from Sicily quite confirms their reputation for inferiority. They are very largely adulterated, and as a rule decidedly rancid.A few single samples from sources not named in the table have also been examined. Thus, some oil from Mitylene proved t o contain as much as 30 per cent. of free fatty acid. A sample labelled " Sfax Fine Olive Oil " gave the following results :- Sp. gr. a t 60' F. . . .. .. .. .. ,9169 Free fatty acid ( = oleic) . . .. .. . . 13.5 per cent. Rise of temperature with sulphuric acid of 97 per Percentage of KOH required for saponification . . Melting point of fatty acids by capillary tube} 280 c, and 28.50 c. method . . .. .. .. .. cent. strength . . .. .. .. . . 43.5OC. 19.38 per cent.212 THE ANALYST. - The Elaidin required 310 minutes to solidify at 19' C., and was dark lemon yellow The oil showed no unusual tendency to dry when tested side by side with olive oil By Renard's process no Arachis oil was found. By the Miliau-Stock test no cotton oil was found. The melting point of the fatty acids is quite abnormally high, and so also is the specific gravity, considering the large percentage of free fatty acid in the sample. No conclusions can be drawn, however, from the results yielded by this single sample. Another African oil, from Saffi (Morocco) gave quite normal results. and soft after standing 24 hours at 19' C. of known purity.

ISSN:0003-2654    

DOI:10.1039/AN8891400210

出版商:RSC    

年代:1889

数据来源: RSC

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212 THE ANALYST. DYNAMICAL THEORY OF ALBUMINOID AMMONIA. BY ROBERT B. WARDER.* THE following investigation was suggested by committee work of the American Association for the Advancement of Science, on water analysis. It is an attempt to apply well established principles of mass action t o certain questions involved in the determination of albuminoid ammonia. The following points have been kept in view : 1. Can some probable correction be made for the error incurred by stopping the distillation while ammonia is still coming off? 2. What modification of the original method seems rational? 3. What insight can be gained into the nature of the chemical process? The experimental basis of the following paper will be found in Mallet’s report on the determination of organic matter in potable water,? with the addition of some details kindly communicated by Dr.Charles Smart. I. Distillation of Free Ammonia. I n the distillation of albuminoid ammonia, two stages must be distinguished : first, oxidation of the nitrogenous body by the alkaline solution of permanganate; and, second, the separation of ammonia thus formed by distillation. It will be most convenient to begin with the discussion of this second process, which is essentially physical. As in any other case of fractional distillation, water and ammonia both pass from the fluid to the gaseous or vapour condition, in accordance with their respective tensions and mass. Let x = volume of fluid in retort. y = weight of ammonia in retort. x = weight of ammonia in distillate. Then !! = concentration of fluid in retort, X -dx - _ ’‘ - - = concentration of any small portion of distillate.dx dx The coefficient of volatility may be defined as the ratio of the concentration in Designating this coefficient any small portion of distillate to that of the fluid in retort. as k , *American. Chemical Journal. t Report of the National Board of Health for 1882.THE ANALYST. 213 I n the ordinary distillation of ammomia, k is found to be approximately constant, and it will be so regarded here. using zero subscript to denote initial conditions, By integration, log, y = k. log, x + constant; log, p0 = k. log, x,, + constant, or x :. log, 2? = k. log, -:, YO XO X log 2- = k. log -, 9 0 xo a very useful formula for determing the coefficient of volatility and tracing the progress of distillation.Curve A, in the figure, represents y as that function of x defined by equation (2). Wanklyn," who was the first to use and define the term coefficient of volatility, reports four experiments for its determination. One litre of dilute aqueous ammonia was distilled in each case until 50 cc. of distillate had been collected. As nearly one- half the ammonia taken was distilled with the first 5 per cent. of water (the concen- tration in the retort being gradually reduced a t the same time), Wanklyn estimated k equal to " about thirteen or fourteen." The experimental data are given below with more precise values of k, as calculated by equation (2). I n each case, xo = 1,000, x = 950. The quantities of ammonia taken, and that found in the distillate, are expressed in milligrams.under y,, and x respectively ; the difference (remaining in retort) under y : Yo. z. Y. k . 1000 480 520 12.74 1 5 0 *50 13.50 *5 *235 9 6 5 12-39 *2 *095 *lo5 12-55 Mean = 12.8 This value may be rather too low, as no account is taken of a possible loss from imperfect condensation, a loss averaging 7.2 per cent. in Smart's experiments. The same author observes also ? that in the dist,illation of one-half litre of water, the ammonia found in the first measure of 50 C.C. is three-fourth of the whole quantity of ammonia obtained, By equation (a), assuming that any loss affects each part in the same proportion, log 4 = k. lo(. b 3- 1 0 ) .., k = 13.14. Thirty experiments by Smart to determine the loss of ammonia by imperfect condensation are also available for the estimation of k, the successive measures of distillate having been nesslerised separately.$ A single distillation affords several values, as each fraction determined may be compared with the whole quantity found in subsequent fractions.The values thus deduced vary from 10 to 16, with a few instances beyond these extremes. The variations in the values of k do not show any well marked relation to the whole quantity of ammonia present, to the amount of loss, nor to the * Phil. Mag. [4], 45, 132 (Feb. 1873). t Wanklyn's Water Analysis, 6th and 7th editions, p. 41. $Most of these data appear in the Report of the National Board of Health for 1882, pages 312-314.214 TEE ANALYST. rate of boiling. The experimental work was done wholly for another purpose, and probably with just such care as the conscientious analyst would ordinarily give.We may then assume 13 as a mean value for k, remcmbering that considerable allowance must be made for unexplained variations. 11. Application of Fos.muZu t o Bstintation of FTee Ammonia. I n the analytical process it is usual to distill three or four fractions, each nearly equal to one tenth of the original volume. For 100 parts of free ammonia present, when k = 13, theory would lead us to expect, in four successive fractions, the increments named below under Ax, with loss of 0.13 ; vertical lines in the figure, a, a, a, represent these increments geometrically. The ratio of each increment to the next is stated under r. The mean values of the ratios obtained in the experiments t.0 determine loss of ammonia are given under r ’ : NO.A$. 1’. T I . 1 74.6 3.75 4.2 3 2 19.9 4.4 5.26 3 4.5 3 5-4 5.65 4 -84 I n the analyses of natural waters reported, considerable variation appears in the ratios of successive inclrements, but usually not more than might be expected from the observed variations in k. Analyses No. 18 and No. 54 are exceptional and happen to give identical results, the free ammonia being *015, *01, and ~ 0 1 mgm. in the three fractions nesslerised, with ratios 1.5 and 1. I n such cases there is a strong probability that some more complex body is gradually decomposed by simple boiling with sodium carbonate. Small ratios between the successive fractions of ‘‘ free ammonia ” may lead to suspicion of urea contamination, though of course due caution should be used in drawing such conclusions.The analyst will at least find it instructive to enter the ratios in his note-book, together with the separate results of nesslerising; this will appear more plainly in the following sections. The slowness of the chemical action usually retards the distillation of albuminoid ammonia, giving rise to much smaller ratios between successive fractions than those named above. 111. Action of Mass in Pormation, of Albuminoid Ammonia. We must now attempt to follow the chemical as well as the physical aspect of the process. In the former the reactions may be much involved, and various formulas may be required to represent the successive formation and destruction of different substances.Let us consider, as an ideal case, a single chemical reaction, involving one molecule each of three reacting bodies; the formation of ammonia taking place a t each moment of distillation, in each cubic centimeter of the fluid, in proportion to the product of the quantities of the nitrogenous body, the potash, and the permanganate present therein. Retaining the use of x, y, and x as explained in section I, let u, = weight of the nitrogenous body in the retort, v =weight of potash in the retort, w =weight of potassium permanganate in the retort, t =time, in minutes, from the beginning of the reaction, a = coefficient of speed.THE ANALYST. 215 Assume also a uniform rate of distillation, in which 6 =volume distilled per minute, bc =volume of fluid in retort at the beginning of the action ; whence 6 4 and ClX= - bdt.x -= - u v W Then - -, and =weights of the three active substances in each cubic centimeter of x ’ x X fluid in the retort, - du. d t CEX ---- dzt- b - =rate of change, and, by the law of mass action, du u v w ZG b- = c b . - . _ . -. x=avw. - Ix;2 7 ClX x 2 x : The reagents are present in such large excess that ZI and w may be regarded as constants (unless the permanganate suffers from an unusual amount of pollution), and by integration, UVUI 1 b x log, u= - - . - +constant, avw 1 log, zc0= - -__ - - +constant, 6 xo 5% avw xo-x :. log, - = - __ . - u.0 b xox ’ which may be written (4) zt avw xo --x x, - x . - - A * - -. -log- = U O 6x0 log, 10 x X This equation represents any one reaction of the kind specified during the concentration required in an ordinary estimation of albuminoid ammonia, but the mathmetical expression must not be pressed too far.Thus, if we make x = 0, this not only implies that the contents of the retort are evaporated to dryness, but also that the reagents have gained infinite concentration, and therefore act with resistless force, effecting complete alteration of any remaining traces of the nitrogenous body. The form of the curve varies greatly with the value of A . Two examples are given in the figure, Curve B represents this equation when A = 1 ; curve C when A = &. Since the quantity of ammonia present at any moment (both in retort and distfiIate) is pro- portional to the weight of the nitrogenous body transformed we may write where subscript c/3 is used to denote the ultimate value theoretically possible ; or, in another form (since y,= 0), ZCO - u : zc, : : (y + 2) : (y + a), , u.- - x , - ( y + x ) (5) u.0 x, The curves B and C ar0 80 drawn that ordinates represent (y + x ) as a function of x. It will be seen at once that when A = 1 the quantity of ammonia increases very rapidly during the first part of the distillation, but when A = 0.1 (y+x) increases but slowly until the fluid is considerably concentrated. Equation (4) suggests various modi- fications by which A may be altered at pleasure; for example, by increasing the quantity of permanganate used (represented by w), or by distilling a less quantity (6) each minute. Thus Smart noted several instances of increased action by slower boiling.EXPLANATION OF THE FIGURE. a, a, a. Fractions, each & the original volume. E. Ammonia in retort, from curve B. A . Curve of distillation of free ammonia. the original volume. B. Formation of albuminoid D. Ammonia is distillate, from curve B. Value of x, although positive, are ammonia, eq. (7) ; A = 1. d, d, d. Fraction$, each measured towards the left, in order that time may be counted tomards the right. C. Formation of albuminoid ammonia, eq. (7) ; A = &.

ISSN:0003-2654    

DOI:10.1039/AN8891400212

出版商:RSC    

年代:1889

数据来源: RSC

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THE ANALYST. 217 REPORT OF' RECENT RESEARCHES AND IMPROVEMENTS IN ANALYTICAL PROCESSES. THE SEPARATION OF COPPER FROM ANTIMONY. FINKENER. Mittlz. KonigZ. tech. Versuch, lS89.-The separation is effected in two stages : first by the precipitation of the bulk of the copper, as cuprous iodide in an acid solution, and then by the removal of the remainder as sulphide in an ammoniacal solution. The author has established the following, which serve as a basis for the method :-(1.) Cuprous iodide carries down antimony even in the presence of tartaric acid from a nitric acid solution of the two metals, but does not do so if the antimony be first converted into a double salt of antimony pentafluoride and an alkaline fluoride by the addition of the latter. (2.) Free iodine in the presence of an alkaline fluoride converts antimony trifluoride into the pentafluoride. (3.) Sulphurous acid reduces antimony pentafluoride slowly in the presence of potassium iodide ; the addition of hydrochloric acid hastens the reaction, but the presence of potassium fluoride almost completely inhibits it.From this the following method is derived :-If the solution to be treated contain the antimony as a pentad compound, all that is necessary is to add an alkaline fluoride, then potassium iodide and sulphurous acid; heat gently, filter off the bulk of the copper as cuprous iodide, and wash with boiling water, made acid with sulphuric acid. I n the event of the antimony being in the triad state the solution may be first treated with chlorine or bromine water, or oxidation may evsn be effected by the iodine liberated by the action of the cupric salt also present on the potassium iodide, provided time be allowed for it before the addition of sulphurous acid.The filtrate containing all the antimony and a little copper is oxidised by bromine water, and the metals pre- cipitated together by sulphuretted hydrogen, the mixed sulphides dissolved in hydro- chloric acid with the addition of potassium chlorate, ammonium tartrate added, and ammonia in excess ; the resulting solution is heated on a water-bath and sulphuretted hydrogen added, until no further precipitation occurs. By thus minimising the quantity of ammonium sulphide present, re-solution of cupric sulphide is avoided. The filtrate containing only the antimony is acidulated with sulphuric acid and sulphuretted hydrogen passed through ; the antimony is determined in the sulphide thus precipitated by heating it, together with its filter, with hydrochloric acid, and determining the sulphuretted hydrogen evolved by standard iodine solution.The author has established that antimony sulphide, precipitated in the presence of sufficient ammonium tartrate to convert all chlorine present into ammonium chloride, is of normal composition, and yields the theoretical quantity of sulphuretted hydrogen when heated with hydro- chloric acid. The analytical results show the method to be reliable, if potassium or sodium fluoride in the proportion of about 1 grm. to 0,275 grm. of antimony be used, and the solution in which the first stage of the separation is effected be about 200 C.C.W. H. D. ABNORMAL APPEARANCE OF CHOLEREXTIN. J. B. NAGELVOORT. Nederl. Eydschr. v. Pharmacie, etc. October, 1889.-A sample of cod liver oil submitted to the author was tested in the usual way for phytosterin, and, indeed, the well-known needle-shaped crystals were obtained, apparently showing the presence of a vegetable fat. On applying the chemical tests, it was, however, proved to be cholerestin, On repeating the process,218 THE ANALYST. Oils. the author succeeded in getting the proper crystals, but he fears their shape may be influenced by temperature, concentration of the liquid, and rate of evaporation, and, therefore, the mere appearance counts for nothing. The following reactions serve to recognise cholerestin : Sulphuric acid gives a reddish-brown, turning to dirty green on adding a drop of water.A mixture of equal parts of chloroform and sulphuric acid gives a violet colour, changing to red and immediately discharged by a drop of water. L. DE K. In the natural state. ON THE ANALYSIS OF OLIVE OIL. RIOUL BRULLE (Rev. Interrial. des FaZsiJcation, Oct. 15, 1889).-For the testing of olive oil, the author employs argentic nitrate in the presence of fuming nitric acid. The argentic nitrate decomposes violently, and produces metallic silver, with a coloration depending exactly on the nature of the oil employed. If we mix 10 C.C. of an oil with 0.5 C.C. of fuming nitric acid in a porcelain capsule, heat, and shake the mixture violently until a foam has been produced, we obtain different colours, according to the oils employed.We, however, take lio notice of these, but go on with the process by adding 5 C.C. of a 25 per cent. solution of argentic nitrate in alcohol of 90'. Still applying heat,a moment arrives, at about 115' C, when the argentic nitrate decomposes, and deposits metallic silver. Having reached this point and continued to heat until the first flecks have just disappeared, we observe, on the one hand, the coloration of the slight oily stratum, which is easily seen by slightly inclining the capsule; and on the other hand, the metallic flecks glistening on the surface of the liquid. On saponifying the oils, and treating them by the same method, the colora- tions obtained are all different, as may be seen by the following table :- Oily strata.Orange Raw sienna Persian lake Gold ochre Deep chrome Black Burnt carmine" Gold yellow I Flecks. Brownish green Cobalt violet Bright violet Blue 9 7 Green [blue Ultramarine 9 , 9 , I Colorations obtained. I oily strata. Olive Cotton Sesame Ground-nut Poppy-seed Gold-of -pleasure Linseed Colza Olive green Green Chrome green Sap green Olive green Persian lake Dragon's blood Persian lake Flecks. Green Terra vert China blue Emerald green Pale greenish blue Bright blue Emerald green Brownish green * After becoming cold, i t forms a crystallization of blue-coloured needles on the surface. The designations of the colours are those used in water-colour painting. I n com- paring the tint of any mixture of oils treated by this method with those given in the above table, a chemist will, after a little experience, be readily able to prove the presence of a seed oil in olive oil, as well as to detect adulterations as low as 5 per cent,, and to name the foreign oil present in the sample.M. 8. A. M.THE ANALYST. 219 Galactose. 250 m.g. 237.5 225.0 2125 200.0 187.5 175.0 162.5 150.0 137.5 125.0 11 2.5 100*0 87.5 75-0 62.5 50.0 37.5 25.0 Copper. 434.5 m.g. 411.8 393.6 375.0 354 *2 335.0 316.4 297.6 277.5 254.0 232.7 211.1 188.7 165.4 142.4 120.2 94.8 73 *1 49.9 H. D. R. REVIEWS. COLOURED ANALYTICAL TABLES SHOWING THE BEHAVIOUR OF THE MORE COMMON METALS AND ACIDS TO THE ORDINARY REAGENTS, WITH SPECIAL REFERENCE TO THE COLOUR OF REACTIONS. A CLASS-BOOK FOR STUDENTS IN HOSPITALS, COLLEGES, AND SCHOOLS. BY H. WILSON HAKE, PH.D., F.I.C., F.C.S.London : G. Philip & Son, Fleet Street. THIS book, with so voluminous a title, and a preface nearly filling two pages, is simply a set of the usual sort of imperfect analytical tables served up to the budding aspirants for ordinary medical primary examinations, and suficiently full to get them through their arduous analytical labours in the (so-called) class of practical chemistry. It, how- ever, differs from all other books with which we have met (except Dr. Simon’s ‘‘ Manual of Chemistry,” published in 1885 and reviewed a t the time in our columns), inasmuch as that, attached to each test there is a picture of a test tube showing a hand-painted representation of what the colour of the precipitate should be (supposing, of course, that the atudent works properly) ; and there are also similarly coloured representations of blowpipe beads, and charcoals, and of bunsen flames.What real advantage there will THE VARIOUS OXIDES, SALTS, PRECIPITATES, FLAMES, BORAX-BEADS, AND BLowPrPE220 THE ANALYST. - be to tho student other than enabling him to skulk his practical chemistry class even more than he now too often does, and grind up a t home, it is difficult to see. But that it will be useful to the unfortunate demonstrator who is expected to teach practical chemistry to perhaps thirty men all at once, is quite evident. This is the real use of such illustrated books; and Dr. Hake lets the cat out of the bag in his preface, when he says : (‘ The book, I believe, should prove of service in schools, or in large classes where individual attention from the teacher becomes difficult, or almost impracticable ; and medical students who, under the present regulations, have a good deal of simple analysis to learn in a comparatively short space of time, will possibly find their labours lightened by its use.” There is no doubt that all those hospital and school teachers who like to take the least possible trouble over their work will find it well worth their while to quietly introduce Dr.Hake’s illustrated tables to the notice of the class. Like many such books, it is here and there a little slipshod, as witness the paragraph on metals, in which a student, having been told that he must not use HCI, but nitric acid, to dissolve Pb, Hg, and Cu, is yet left in doubt as to whether he might not use hydrochloric acid for Ag.Surely it would have been just as easy to put the Ag in the nitric acid set and be done with it. So far as the colouring goes, it is really very well done indeed, and quite amusingly natural in many cases, and as we said before, the book is a real boon to the overworked or lazy teacher, and to the ‘‘ wagging ” student. LAW NOTES. CONDENSED SKIM MILK.- An oilman named White, carrying on business in Camberwell-road, was summoned at Lambeth Police Court, for selling condensed milk not of the substance and quality represented, according to the terms of the Adulteration Act.-Mr. Biron, barrister, instructed by Mr. Marsden, vestry clerk of Camberwell, appared to prosecute ; the defendant was represented by Mr.Besley.-George Dewey, one of the inspectors of the Camberwell Vestry, stated that he went to the defendant’s shop and asked for three tins of condensed milk, White asked him what brand he would have, and he replied the ‘‘ Standard ” brand. He paid 9d. for the three tins. Witness now produced the certificate of Dr. Bernays, the analyst for Camberwell, which showed that 90 per cent. of the cream had been abstracted.-Dr. Bernays in his evidence stated that, the certificate produced was given by him, The label upon the tins sold was as follows : ‘‘ The Standard Brand is specially prepared from the richest cow’s milk from which a portion of the cream has been removed, and nothing added but cane-sugar. I t is better and cheaper than fresh milk for ordinary purposes.Five parts of water to one of milk, and for infants 8 to 15 parts water, according to age.” There had been nothing added to the milk but cane-sugar.-By Mr. Biron : Such a prepara- tion so diluted would not be fit food for infants.-Mr. Fesley said the “ Standard ” hrand was a good milk, and then proceeded to quote several decisions with regard to such cases, and contended that the defendant was not liable.-The defendant was called and stated that he sold the milk in question and other brands at 3d., 4d., aid., and 54d. He declared that he told the inspector it was partly skimmed, and was sure he called the attention of the officer to the labels on the tins, which showed it was skimmed milk.-Some legal arguments followed, and Mr. Biron (the magistrate) said it no doubt was an important and difficult case.Under all the circumstances, however, he felt bound to con- vict, although at the same time he was fully satisfied the defendant was without the slightest blame or had any intention to defraud. . He should, therefore, only be too willing to grant a case for the various points to be argued in a superior Court. He considered the sale was one to the prejudice of the purchaser under the Act, and he therefore ordered defendant to pay a fine of 20s. and costs,- Notice of appeal was given. CORRESPONDENCE. [The Editor is not in any way responsibb f o r opinions expressed by his correq?ondents.] l’o the &%tor of the ANALYST. SIR,-In your current issue you are correct in ascribing to me the first mention in your columns of the phenolsulphonic test for nitrates and the napthylamine test for nitrites in water (Vol. x., p. 199 ; Vol. xii., pp. 50,152). It will be seen by reference to my papers that the extract from Dr. Leffmann’s book approaches very nearly to a copy of my words. The same weights are given for preparing the reagents, and the same precautions directed to be observed. The only practical differences I have noticed are, the introduction of a glass rod with which to stir the mixture, and an error in the chemical formula. I am, etc., There were several other brands there, Phcenix Mills, Dartford. A. PERCY SMITH, October 3rd, 1889.

ISSN:0003-2654    

DOI:10.1039/AN8891400217

出版商:RSC    

年代:1889

数据来源: RSC