摘要:

THE ANALYST. APRIL, 1890. ON THE SOLUBILITY OF PHOSPHATE OF ALUMINA LN ACETIC ACID WITH SPECIAL REFERENCE TO THE ESTIMATION OF ALUMINA IN FLOUR, BREAD, ETC. BY W. C . YOUNG, F.I.C., F.C.S. (Read at Meeting, Tebruary, 1890.) IN previous communications to the Society I have called attention to the solubility of phosphate of alumina in acetic acid and its effect upon the ‘‘ logwood ” test. I propose in this paper to show to what extent this solubility affects the processes in use for the62 THE ANALYST. determination of alum in bread, etc., where the phosphate of alumina is precipitated in the presence of free aceticauid, and the influence exerted by the acetate of ammonium and other compounds present in solution and by proceeding in a variety of ways. The solutions used in the experiments to be described were of the following strengths, viz, :-Alum, 100 C.C.= *I gram. potash alum, phosphate of sodium, 100 C.C. = 20 grams. acetate of ammonium, 100 C.C. = 20 grams. acetic acid, commercial pure. The experiments were made in the following manner : 100 C.C. of alum solution taken in each case (the quantity of alumina present representing the amount that would be obtained from 100 grams. of bread containing about 20 grs. of alum in 4 lbs.) No. 1. 5 C.C. acetic acid, 2 C.C. phosphate of sodium solution, and 5 C.C. metate of ammonium solution added, boiled and then filtered. No. 2. 5 C.C. acetic acid and 2 C.C. phosphate of sodium solution added, boiled, then 6 C.C. acetate of ammonium solution added, again boiled, and then filtered.No. 3. 5 C.C. acetic acid, 2 C.C. phosphate of sodium solution, and 5 C.C. acetate of ammonium solution added, set aside in the cold and filtered as soon as the precipitate settled. No. 4. 5 C.C. acetic acid, 2 C.C. phosphate of sodium solution, and 5 C.C. acetate of of ammonium solution added, set aside over-night, then filtered. No. 5. 5 C.C. acetic acid, 2 C.C. phosphate of sodium solution, and 5 C.C. acetate of ammonium solution added, boiled, and set aside over-night, then filtered. The various solutions were added in the order given above. I n every case the liquid remained quite clear in the cold until the acetate of ammonium solution was added, when a precipitate commenced to form. In the case of experiment No. 2, a precipitate formed on boiling, which, after addition of acetate ammonium, became very dense, much more opaque and apparently larger in bulk than any of the others.The results obtained, stated in grams., are as follows :- A. B. C. Dlean, 1. *0230 -0230 -0210 *0223 grammes. 2. -0250 -0245 00250 -0248 7 9 3. -02 I a -0220 *0205 *02 143 9 7 4. -0226 -0225 -0215 *0222 7? 5. 4226 00225 *0230 9227 7, Theory gives -0258. 7 7 It will be seen from these figures that in every case the result was below theory, the nearest approach beicg in the case of experiment No. 2. It is curious that in No. 2 the character of the precipitate obtained differed from all the others and was larger in amount, as the only difference between it and No. 1 was that the solution was boiled after the addition of the phosphate of sodium, and again after adding the acetate of ammonium, whereas in No.1 all the solutions were added before boiling. On comparing No. 1 and No. 5 it will be seen that there is very little difference, showing that after precipitation by boiling the phosphate of alumina does not redissolve by long contact with acetic acid of ths strength employed in these experiments, The increase in the precipitate by boiling is shown on comparing No. 1 with No. 3. The in- The lowest result obtained was in No. 3, as was to be expected.THE ANALYST. 63 fluence of the acetate of ammonium being so very marked I repeated experiments 1, 3, and 4, using in each case 1 C.C. of acetate of ammonium solution, or a fifth of the quantity used before, when I got the following results :- 1.*0185 3. No precipitate. 4. -0108 ,arms. Experiment No. 2 was also repeated, using 15 C.C. of acetic acid and no acetate of ammonium, the result being 00165 gram. No. 1 was the result obtained by filtering immediately after boiling, No. 3 in the cold, and No. 4 after boiling and setting aside over-night. No. 2 shows the degree of solubility of phosphate of alumina (precipitated from a boiling solution), with a large excess of acetic acid in the absence of acetate of ammonium. These results show very clearly that the quantity of acetate of ammonia present has a grsat influence on the solubibity of phosphate of alumina i n acetic acid, I n order to ascertain if the quantity of phosphate of alumina dissolved increased with the proportion of alum present, I repeated the five experimsnte, using a -3 par cont. solution of alum, with the following results : - A. B. e. Mean. 1. *04s0 *OAT5 00270 -0475 gramrnos. Y . 4505 *OSOO - 0 50( ) -0502 9 , 4. a0450 ‘0460 -0460 -0457 9 ) 6. -0470 *04 60 -0450 -0460 9 7 Theory give3 *a51 6 > ? > r ) . a0445 -0440 -0435 -0440 3, On comparing these figures with the first series it will be seen that the loss in The following experimentg, in which 15 cc., instead of 5 c.c., as in the former evcry case is slightly increased. were used, show the effect of a large excess of acetic acid.

ISSN:0003-2654    

DOI:10.1039/AN890150061c

出版商:RSC    

年代:1890

数据来源: RSC

摘要:

THE ANALYST. 6 3 THE ANALYSIS OF CARBOLIC AND SULPHUROUS DISINFECTING POWDERS. BY JOHN MUTER, Prr.D., F.R.S.E. Read at Meeting, March, 1890. WEIEN our Secretary pressed me to read a paper to fill up an apparent void at the February meeting, I thought that it would not bs uninteresting to initiate a discussion on this subject, which is daily becoming more and more important to public analysts. Local authorities are waking up to the use of the analyst as a protector of their in- terests against the deceptions too often practised by unscrupulous pmsons, and there- fore it is well that some agreement s h d d be come to among ourselves as to the best process to employ, and also as to the best form of tender to be recommended for use by such bodies in obtaining contracts. As the latter has become really a very burning question, both to the purchasers and the trade, I propose to take it first.The common, loose form of contract is for “carbolic acid powder cmtaining 10 (or perhaps 15) per cent. of liquid carbolic acid at so much per ton,” to which is frequently added thestipulation that “the base shall not b3 lime.” If the words of such contract are to be interpreted in a strictly chemical sense, viz : that the powder shall contain 10 to 15 per cent. of absolute phenol, the whole thing becomes a farce; because no such64 THE ANALYST. powder could be produced under a cost that would be absolutely prohibitory. All chemists know that the article commonly sold as “ liquid carbolic acid ” is not absolute phenol rendered liquid by the addition of 5 to 10 per cent of water, but consists of the higher phenols of coal-tar (chiefly cresol) from which the phenol itself has been nearly absolutely removed. Cresol has been held to be just as good an antiseptic as phenol, provided that it be in a free state, and especially not combined with lime.I t s com- paratively cheap cost, moreover, has caused it to be almost entirely employed in the manufacture of carbolic powders. Why, therefore, should this fact not be openly recognised, and all sorts of difficdties saved at once to the manufacturers, the medical officers of health, and the analyst. An analyst dealing with such a powder, and most probably employing the process originally described in the ANALYST for October, 1887, or some modification thereof, naturally reports that the powder contains so much per cent.of tar phenols (chiefly cresol) ; this report being laid before the authorities, some one immediately starts up and exclaims, “This is not what we want ; we contracted for carbolic acid,” and then tho difficulty begins. An appeal is made to the medical officer, and he, answering on the spur of the moment, without an opportunity of conferring with the analyst, may simply increase the difficulty. That this is no fancy picture is evidenced by the fact that it has actually occurred in many cases, and I have a t the moment in my mind an instance in which a firm, having taken such a contract, have lately been threatened that they will be compelled to supply a powder containirg 10 per cent. of pure, absolute phenol, the medical officer declaring that he contracted for carbolic acid, by which he means phenol, and nothing else.I n some districts the powder is also required to contain 5 per cent. of sulphurous acid without the use of the word ‘‘ available,” and some day we will probably meetl with the reductio ad absurdurn in the shape of a demand by a medical officer for such a powder containing 5 per cent. of free sulphurous acid-a chemical absurdity. I would therefore submit t o you for considera- tion the advisability of impressing your Boards and the manufacturers with the necea- sity of ceasing to employ trade misnomers, and of contracting for a powder, the base of which shall be gypsum or siliceous matter, and which shall contain a certain per centage of uncombined tar phenols (chiefly cresol), and also, if desired, 5 per cent.of available sulphurous acid. I feel satisfied that in our progressive times nothing is lost, either to manufacturers or to consumers, by calling a spade a spade. Turning now to the analytical question, I will proceed to make a few short re- marks as to the basis of what will, I hope, prove to be an interesting discussion. I still estimate the phenols in carbolic powders by the process described by Mr. Do Koningh and myself in the ANALYST for October, 1887, nor, despite the criticisms which sub- sequently appeared by Mr. Williams in the Journal of Chenzicnl lizdustry, have I seen any necessity to alter it. The only modification I have come t o in practise consists in employing 150 C.C. of 10 per cent solution of sodium hydrate instead of 200 C.C.of a 5 per cent. solution. It must also be remembered by all persons using the process that the acids, when measured over the brine, contain about 5 per cent. of water ; because we have proved by experiment that commercial anhydrous cresol shaken up with brine absorbs this amount. Speaking of commercial cresylic acid, our salt test (described in the same number ofTHE ANALYST. 65 - the ANALYST) is a good and ready test to enable one to rapidly decide whether a given sample of cresol really contains water or not. Really anhydrous cresol when shaken up with three volumes of brine, gives an increase in volume of about 5 per cent. If the cresol is watery, it will either not increase in bulk a t all, or it will decrease slightly.The test is of course only a sifeguard against gross frauds, and for the really accurate estimation, I use the distillation process, which, when not carried too far, will enable us to read off exactly the c.c.’s of water. The amount of cresol dissolved in the water is so slight that it may be disregarded; but, on the other hand, if any appreciable amount of acid has come over, about one-tenth of its volume must be added to the water. The ordinary cresol of commerce usiially contains some napthalene, and a rapid method of getting a t a fairly accurate idea of its amount is a desideratum. This presence of naphtalene is often preferred by the purchasers who have the idea that, if “corn- rnercial carbolic acid ” becomes milky when pit into water, it shows its strength.The process I have described is as follows :- 50 C.C. of the acid are shaken up with 200 C.C. of 10 per cent. solution of sodium hydrate, when the acids readily dissolve, leaving the naphtalene floating on the top. The bottom liquid layer is run off, a washing of 5 per cent. solution of sodium hydrate is put on, and the whole is rapidly filtered through a quick filter and allowed to drain. The collected naphtalene is then rineed off the filter into a small beaker with water, and is then once more collected on a pair of counterbalanced filtersin the usual manner. After draining, the filters are removed from the funnel and dried as far as possible between blotting paper by judicious pressure. The filters are separated, and the inner one and its contents are weighed, using the outer one as a tare. The amount of moisture held by the two filters is sufficiently alike to enable us to get a very fair approximation to the true amount of naphtalene, quite nearly enough for ordinary purposes.Taking now the analysis of sulphurous powders, the process I use for the estima- tion of the available sulphurous acid is as follows :--- Two grams. of a fair sample of the powder are placed upon a small filter, and percolated with anhydrous ether until the phenols and tarry matters are removed, which is readily and quickly attained. 50 C.C. of decinormal iodine solution are then placed in a, bottle, and as soon as the ether has dried off from the powder, the con- tents of the filter are dropped into the bottle. The bottlg is allowed to stand for half- an-hour (being shaken a t irtervals,) and, finally, the contents of the bottle are titrated back with decinormal “ hypo ” in the usual manner.The amount of iodine destroyed of course represents the available sulphurous acid in the two grams. of powder started with, and, therefore, it is only needful to multiply the number of C.C. of iodine used by 0 0032. This method I find to work well with every sort of powder in the market, pro- vided its base be not lime. To get a really satisfactory process in the presence of a lime base is very troublesome, and I cannot say that I have yet met with one that is a t once rapid and good. If any member of the meeting knows one, he would be doing us all a favour to give it to us. reversion.” Sulphurous powders oxidise with great rapidity, and a perfectly honestly-manufactured one may, if badly kept for even a very short time, show, on analysis, a much smaller portion of available We come now to the important questiou of66 THE ANALYST.~ sulphurous acid than it ought to do. It is, therefore, the duty of an analyst de- sirous of holding the scales of justice fairly, to try, if possible, to ascertain the amount of such reversion. With a powder made on a gypsum base and with calcium bi- sulphite I am not aware that this is attainable; but many of the leading makers recog- nising this, are so constructing their powders as to render it possible. Some use a purely siliceous base, containing only a neglectable quantity of sulphate, while others use a gypsum base, but put in the sulphite in the form of a specially-manufactured sodium salt.It would, a t first sight, appear that the analysis of such a powder is a very simple matter, but this is not so. The whole thing is complicated by the fact that the moment waber is put upon the powder, a double decomposition occurs, and we get insoluble calcium sulphite and sodium sulphate ; and we find, in practice, nearly the whole of the sulphurous acid in the insoluble residue. To get at the reversion in such powders I have devised the following method :-- 20 grams. of the powder are put into a bottle, and 200 c,c. of water are measured in with a pipette. After an occasional shake, the whole is allowed to settle, and some of it is poured off or filtered through a dry filter.The decomposition above alluded to often occurs a t this stage of the process; but, as will be seen, the latter is not thereby affected. 20 C.C. of the liquid (= 2 grams. of the sample), are mixed with an excess of bromine, and filtered from any bromo-sresol remaining undissolved. It is then treated with an excess of barium chloride, and the total sulphuric acid is weighed as barium sulphate. As, however, a part of this is due to dissolved calcium sulphate, another 20 C.C. are precipitated with ammonium oxalate, and the lime weighed as car- bonate. The calcium thus found is now calculated to its equivalent amount of sulphuric acid, and this is deducted from the total. The remainder is still further reducad by deducting an amount of sulphuric acid equivalent to the sulphurous acid previously found by the iodine method, and the remainder represents the reverted sulphurous acid, and is calculated as such.If the powder be made with a siliceous base, it may be more convenient for those who, only doing the analysis now and then, prefer a gravimetric method, to proceed as follows :- Drop two grains. of the powder into a beaker containing an excess of bromine water, and while this is acting, take another 2 grams., put it into a dish, and moisten with fuming hydrochloric acid (free from chlorine). Now evaporate to dryness, re- dissolve, and then throw down the sulphate with barium chloride in both parts. The difference between the two results calculated to sulphurous acid will give the amount of that body present in tho 2 grams.of sample taken. If the base be all but free from sulphates, we thus get a fair idea of the probable reversion a t the same time. DISCUSSION. Mr. BLOUNT said that a superstitious value was generally attached to the dis- infecting powers of the lower tar acids. I n the specification for creosote used by the Crown Agents for the Colonies and in vogue among engineers, it was laid down that the creosote should yield ncjt less than 10 per cent. of tar acids, of which a t least half '' is to be carbolic acid, distilling at a temperature not exceeding 450" E. " (233s C.). Having regard to the ambiguity of the term '' carbolic acid," and the risk of its being looked upon as equivalent to phenol, he preferred in reporting upon samples examined underTHE ANALYST, 67 ~- __ this specification to use the phrase ( I tar acids distilling below 450’ F.” as more accurate. It sometimes happened, however, that a client stickled for “ carbolic acid,” in which case he was accustomed to write the words in quotation marks, and indicate that the specification was responsible for them.As to the question of extracting the tar acids, most of the creosotes he saw were of good quality, and yielded more than 10 per cent. of tar acids when the distillate below 610° F. was extracted with caustic soda, thus complying with the specification ; but such samples as only just contained the permitted minimum of tar acids, and from which it was therefore important in judging them to get out every tram, were distilled to the point of pitching and then extracted.Mr. CASSAL said that in the analysis of creosotes he had found that unless the dis- tillation was carried to the point of pitching, the whole of the ‘‘ tar acids ” were not got out. He had found, further, that the passing or condemnation of a sample might de- pend upon the difforence made by carrying the distillation to this point. Particular specifications had to be followed in which, as a rule, certain definite percentages of ‘ I crude tar acids ” were mentioned. I n one with which he had frequently to deal, the amount of ‘ I crude tar acids ” was fixed a t 8 por cent. for creosote intended for the treat- ment of timber, and this couId certainly not be regarded as a high standard to take. Specifications for the supply of carbolic powders and liquids were, like those in use for creosote, of a very variable character.There were, in fact, all sorts of specifications and all sorts of rules laid down ; it was very desirable to find out according to what autho- rities they had been prepared, and if possible to arrive at some sort of understanding upon the whole matter, which was a t present in a state of much confusion. He desired to mention further, firstly, that he had found it necessary in determining the tar acids to wash repeatedly with the soda solution in successive separate quantities ; and secondly, after the separation of the acids to allow them to stand over the salt and acid solution €or a t least twelve hours. When these steps were not taken, the results were always too low, and sufficiently so to make a considerable difference.Referring to the use of the term “ Carbolic Acid,” Mr. Cassal said that it could not be taken as synonymous with Absolute Phenol. The term “ Carbolic Acid ” had a1 ways been applied to a mixture of phenol bodies ; this was the recognised trade mean- ing of the term, and to assert that it meant absolute phenol was to take an improper advantage of the existing confusion in chemical nomenclature. He agreed with Dr. Hunter as to the unnecessary difficulties introduced by such a proceeding. If medical men and sanitary authorities, for reasons no doubt best known to themselves, but which they would find it difficult to specify, required absolute phenol to be supplied to them, they ought to use the proper chemical term, and they would then be justified in calling upon the analyst to decide whether they had been supplied with what they had asked for.Mr. ADAMS said that phenol was much more active as a disinfectant than as a deodorant, and there was a great difference between the two. As a true disinfectant, he thought the medical profession generally held phenol as the best of all the tar acids. Speak- ing for himself, he had not much confidence in any ; he was quite positive that, in the ordinary way in which they were used, they exert no power as bacteriacides. He had several very interesting facts in connection with that point, and on0 m i s so clear that it was worth relating there. Many years ago he had some papers brought to his house from the secretary to his hospital. He knew that some of the secretary’s children had just died of violent scarlet fever, and was consequently rather anxious about his own children; he therefore drenched the papers with a strong solution of carbolic acid, and then placed them in a window at the top of his house, exposed to the sun and out of reach, as he hoped, of his children.He was working one day a t a lathe in this room,68 THE ANALYST. ~~~~ ~ when one of his little children got hold of some of the papers. He took her at once and washed her hands, but after three days that child had tho scarlet fever. A more distinct proof of thesource of infection than thatcould hardly be. He did not pretend that the whole of the papers were drenched through and through, but all the outside was, and they were exposed for months in the sunlight. Personally, therefore, he had very little belief in the use of carbolic acid as a bacteriacide; but still he did consider it was a valuable disinfectant. It had an inhibitory power over the germs, and for the time suspended their activity, but as soon as the carbolic acid had evaporated, unless it was sufficiently strong, it left the bacteria as active as ever. He could mention many other instances which had caused him to come to the conclusion that coal tar acids were use- less for the positive destruction of disease germs. He had a different opinion about sulphurous acid, but the ordinary way Of burning a few ounces of sulphur in a large room was not enough. A pound to a thousand cubic feet of space was required.

ISSN:0003-2654    

DOI:10.1039/AN8901500063

出版商:RSC    

年代:1890

数据来源: RSC

摘要:

68 THE ANALYST. ON THE CHROMATE TEST FOR LEAD I N WATER. BY SIDNEY HARVEY, F.C.S., F.I.C. Read at iyeeting, March, 1890. As my paper (‘ On the detection of lead in potable Waters by means of Potassium Bichro- mate,” published in the ANALYST for 1881 (vol. 6, pp. 146), has apparently escaped the notice of several chemists, and as I have since had abundant opportunities of testing the extreme delicacy of the chromate reaction, I feel justified in again drawing the attention of analysts t o the subject, referring for full details to my previous paper. The H,S test for metallic impregnation is of course a most essential one, but it is not always safe to ascribe the colour thereby struck to lead thus ignoring the possible presence of copper and tin, and it is most desirable before proceeding to quantitative re- sults to be sure of the presence of the very metal suspected.For the purpose of proving the presence of lead nothing in my experience exceeds the delicacy of the chromate reaction, which is performed as follows :- Half a litre of the water in question, if it can be spared (otherwise quarter of a litre will do), is placed in a conical precipitating jar (Phillips’s) about two grains of K,Cr,O, are added, and dissolved by agitation. The mixture is set alongside another jar containing “ lead-free ” water treated in a similar manner. It is assumed that the water is quite clear, if not it must be carefully filtered to render it so; the addition of any acid i s objectionable, and previous concentration is unneccessary and evon injurious. The use of the bichromate in crystals is also essential.Water containing as little as one fiftieth of a grain per gallon of lead will, when thus treated, become sensibly turbid in about fifteen minutes, and the turbidity is rendered the more apparent by contrast with the jar alongside. In about twelve hours, if undisturbed, the precipitate will have completely settled, and the fluid may be poured off to the last drop, leaving the bottom of the jar coated with the PbCrO,, which ltxtter may be rendered much more distinct by mixing it with a few c.c.’s of distilled water, and allowing the same once more to settle in a narrow flat bottom tube. Of course, in the case of waters containing larger amounts of lead than the above, the re- action is much more prompt and decisive. No other metal likely to be present in water will give a similar reaction, and I am inclined to think that this test for lead is amply sufficient for all practical purposes. One fiftieth of a grain per gallon of lsad is eqoivalent to one part in three and a half millions or to one part of PbCrO, in two and a quarter millions, thus demonstrating the remarkable insolubility of chromate of lead. (Conclusion of the Xociety’s Proceedings.)

ISSN:0003-2654    

DOI:10.1039/AN8901500068

出版商:RSC    

年代:1890

数据来源: RSC

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THE ANALYST. 69 DETECTION AND QUANTITATIVE ESTIMATION OF INORGANIC AND OItGRNTC POISONS IN BODIES. BY DR. ANTON SEYIM.’~ INTI~OU u CTION. ALTHOUGH toxicologists have at their disposal a vast amount of chemical literature, I hope this article will be welcoine to many, particularly as it is the result of my own experience and observations. My object has been to find a practical qualitative and quantitative course for the detection of those poisons which are within reach of the public, without troubling about such bodies as bitters, drastics, etc., which, in the present state of science, cannot be detected with certainty, whatever care and material the analyst might waste on the matter. The analysis consists of a preliminary examination, and the regular chemical cocrsa. The expert conducting such an investigation must never omit to make the fullest in- quiries about the case, as often valuable clues will be obtained, saving an immense deal of time and trouble.PRELIMINARY TESTS. ( a ) BZOGCi?. The blood is often in a atate of partial decomposition, particularly if a long time has elapsed between the time of death and the investigation. The reduction of its colouring-matter is more or less complete, so that a spectroscopical examination is, of course, useless. If the blood should be dry, it may be dissolved by water containing a trace of caustic soda. The spectrum of a partially reduced blood mostly shows a con- tinued broad absorption band, which is composed of three lines, viz., two of oxyhaemo- globin, with the hsmoglobin one between. Sometimes the band is accompanied by another line in the red part of the spectrum, which is due to either haematin or me th cemoglobin.If this fourth line is observed, the blood must be tested as to its reaction. If alkaline, this points to methzemoglobin; if acid, to hcematin. The first case deserves but little attention, as a rule, unless there has been poisoning with hydrogen sulphide (which is not likely to originate from the putrefaction process), but the second points to the administration of acids, nitroglycerin, potassium chlorate, or ferrocyanide or nitro- benzol. These bodies will then have to be searched for in the urine and other parts of tho body. In most cases, the only question is to decide whether the blood contains carbonic oxide. I f w0 have to deal with B blood whose oxyhaemoglobin has been completely con- verted into the carbonyl compound, without the reverting process having set in, the detection of the carbonic oxide is easy, chemically as well as spectroscopically.If the blood, however, only shows the lines of the non-reduced or partially reduced hsmatin, the detection of the carbonic oxide is not successful, and, in fact, not likely to be so. Not unfrequently, a blood will have to be examined for carbonic oxide, when in contains carbonylhzmoglobin, oxyhzexnoglobin and hsmoglobin, with perhaps methzmo- globin or hsmatin. In such a case, the presence of the carbonyl compound can only be proved by * Chemikep Zeitung, slightly abridged.70 THE ANALYST. ~ ~ adding ammonium sulphide, and noticing whether the absorption band moves towards the red part of the spectrum.The chemical testing with soda ley, with or without calcium chloride, is not trustworthy. ( b ) Vriize. In testing this, it must be noticed this fluid undergoes remarkable changes whilst the poison is acting; also that many poisons only then pass into it when their physiological action is over. Therefore ascertain, if possible, the quantity of the urine, then look at its colour, notice the smell, test for blood, albumen, sugar, also its behaviour towards barium chloride, both before and after addition of hydrochloric acid. The urine may also contain volatile bodies, balsams, alkaloids, and poisonous metals ; whilst if poisonous doses of potassium chlorate, iodide or bromide have been givan they will be readily detected in this fluid.(c) The contents of the Stomach. After noticing the odour and reaction, t r y whether there is a phosphorescence in the dark. If the stomach has an alkaline reaction, any phosphorescence cannot be due to phosphorus, but is cawed by a fungoid growth, then phosphorus only lights when the contents are acid. The reaction of the contents will, according to circumstances, be acid, alkaline, or neutral. Poisoning caused by corrosive .acids, caustic alkalies, or haloids, is sure to have been recognised by the medical man who conducted the post- mortem examiuation. The odour will not give much information if the contents are much putrefied, But when they are apparently in a good state of preservation, I have often noticed a loath- some, sweetish smell in the case of a decided form of arsenical poisoning.I f the con- tents are solid, it is best to take an aliquot part and digest it in a small beaker with spirits of wine, and finally wash the insoluble matter with ether. The residue must now be rigorously examined with the microscope, which will often show remnants of medicines, pills, or powders. The alcoholic solution may be tested far oxalic acid. In many cases the stomach has been washed out for the purpose of the post-mortem. In this case the sediment of the wash-water must be carefully examined. Many indifferent objects will often be found, such as particles of carbon, fragments of coffee, potatoes, grain, greens or flesh, also crystalline bodies, such as triple phosphate, if the stomach has an alkaline reaction.If seeds are found they must bs well washed with water,’alcohol and ether, sorted, weighed and examined. If particles of arsenious acid are noticed, they may, after being freed from adhering matter, be gently dried and weighed, or dissolved in solution of potassium bicarbonate, and titrated with iodine. When the microscopical investigation is over, it is, in many cases, advisable to take a little of the contents and test for arsenic first, as this is the commonest form of poison. If not found, another portion may be exhausted with water, and the filtrate be examined for soluble metallic salts, more particularly the chlorate, nitrate, iodide, bromide, ferro or ferri- cyanide of potassium. 2.-sPECIAL PART. If the preliminary testing has given no particular indication, I start the chemical The residue analysis.I first of all submit the organs to a fractional distillation.THE ANALYST, 71 left in retort is then exhausted with alcohol to dissolve out any alkaloids, and then afterwards chlorinised for the purpose of testing for metallic poisons. VOLATILE BODIES. The contents of each jar are examined separately. A portion is cut up into small pieces and put into a suitable retort containing water. The first distillation is done by immersing the retort in boiling water for several hours. I then add to the contents a little tartaric acid and once more distil, this time by means of a current of steam. In this way we get two fractions. The first contains the readily volatile bodies, such as alcohol, aldehyde, acetone, chloroform, nitrobenzol, turpentine, camphor, amines, or their sulpho-derivatives.I n the second, the remnants of the first, further fatty acids, carbolic acid, hydrocyanic acid, phosphorus, etc. If chloral hydrate or potassium cyanide * are suspected, the organs are moistened with respectively caustic potash or sodium bicarbonate and distilled from the water-bath, but should it be necessary to conduct a steam distillation from an alkaline fluid, I prefer to first make an acid extract with water containing some tartaric acid, which is then filtered and made alkaline before distilling. If the acid distillate is ready, I properly notice its reaction, colour, odour, degree of turbidity, and particularly its bulk, so as to be able to make a quantitative estimation of any substance (such as alcohol) which the distillate may contain.THE FIRST FIXACTION. ( n ) Test with acid silver nitrate ; ( b ) with ammoniacal ditto (aldehyde) ; (c) with nitroprusside, potash, and acetic acid (aldehyde, acetone). Then test with alkaline per- manganate (d) as follows :-lo C.C. of distillate are mixed with a few drops of potash ley and 1 C.C. of a saturated solution of permanganate and allowed to stand for twelve hours in a closed vessel. If oxidisable bodies are present, reduction soon sets in and the permanganate gets decolorised. The filtrate is then tested for aldehyde with ammoniacal silver. A large increase in the amount of aldehyde points to the presence of alcohol. As is well known, an alkaline permanganate acts differently in the cold than at the boiling heat.I n the cold the following reaction takes place (in presence of organic matter) :- (1) X,Mn20, = Mn20, + K,O + 0, (2) On boiling: It is highly probable, although not yet proved, that in the cold the liberated oxygen will first act on any organic matter before peroxidising the manganic oxide. ( e ) With iodine and potash ley as follows :--In a test-tube I introduce a pinch of iodine, then 10 C.C. of the fluid and 3 drops of a 30 per cent. potash, then heat t 3 50° C., when, owing to.the formation of iodoform, the liquid will get more or less turbid. If the iodine is used up, a little more of it must be added, and its excess finally be removed by cautious addition of potash ley. As iodoform does not always separate in well-defined crystals, the best thing is to agitate the solution with K,Mn,O, + Mn,O, = 2 MnO, + Ma20, + K20 + O3 K,Ma20, = 2 MnO, t K,O + 0, * Supposing there is also a ferrocyanide.78 THE ANALYST.ether and allowing the latter to evaporate. If after a microscopical examination of the residue there is still a doubt, Lustgarten recommends the treatment of the crystals with resorcin and potash to get rosolic acid. (f) With resorcin and potash (chloroform). I n a tube introduce a pinch of resorcin, 1Oc.c. of the distillate, 3 drops of a 30 per cent. potash ley, and warm gently, when the beautiful rosolic acid is soon formed. This test is more delicate than the isonitril test; then however powerful and characteristic the smell may be, it is often masked by the presence of amines.I n regard to the prussian blue test (treatment of chloroform with alcoholic ammonia and potash), although when performed under pressure a good result may be obtained, this test is far inferior to the rosolic acid test. 10 C.C. of distillate are mixed with an equal volume of 90 per cent. alcohol, a little zinc dust is added, then 1 C.C. of hydrochloric acid,and a drop of platinic chloride. After standing for three hours, the liquid is decanted from the undissolved zinc and ths greater part of the spirit driven off on the water-bath. The residue is now diluted with water, rendered alkaline with potash, and shaken out with ether. The ether is evaporated and the residue tested for aniline with freshly prepared solution of chloride of lime, which will produce a blue colour should nitro-benzol have been present.(A) With hydrochloric acid and alcoholic solution of phloroglucin (ethereal oils). This test, proposed by Ihl for the detection of bodies of an aldehydic nature, will often give unreliable results when applied to the distillate of portions of bodies, but it is best applied to the distillate of the urine. Hager’s test for oil of turpentine is best carried out as follows :-A pinch of guaiacum is dissolved in 1 C.C. of absolute alcohol and 5 drops of oil of lemon and the mixture boiled; 10 C.C. of distillate are added and the whole boiled once more. The test only succeeds when notable quantities of turpentine are present and the reagent must be quite fresh. If, however, the distillate should have no action on alkaline permanganate or solution of chromic acid, ethereal oils are out of the question.A quantitative estimation of these volatile bodies will not often be practicable, not so much because no proper processes exist, but chiefly on account of the scarcity of material. Any one who has often had occasion to quantitatively determine alcohol in poisoning cases will often wonder how it is so comparative little attention has been paid to this subject in the works on toxicology and even chemistry. Rarely will the contents of the stomach be in such a fresh condition and the amount of alcohol so large as to admit of the estima- tion of the alcohol by the usual process, viz., distillation and specific gravity, more particularly as the gravity may be altered by the presence of amines.Even addition of mineral acids or even platinic chloride and redistilling will not altogether remove the organic bases. The only way is to oxidise the alcohol to acetic acid and to estimate this volumetrically. I carry out this estimation as follows :-The distillate is once more distilled of€. What passes over in the first quarter of an hour is collected into a receiver containing some dry potassium carbonate. The process ia repeated until we finally have a distillate measuring about 10-20 c.c., mostly strongly ammoniacal. It is put into a high-pressure flask, mixed with 3 C.C. of a twenty per cent. I have slightly modifiod Lustgarten’s test. (9) Zinc dust and hydrochloric acid (nitro-benzol). An exception, however, is the estimation of the alcohol.THE AJY'ALYST.73 solution of potassium bichromate, and, after being placed in a freezing mixture, mixed with about 10 C.C. of strong sulphuric acid, or more if the iodoform test bas been very successful. After closing the' flask it is heated in boiling water for eight hours. After cooling, the contents are put into a flask (kept cool), supersaturated with potash, and boiled until every trace of compound ammonias has completely dis- appeared, which is readily ascertained by exposing to the vapours a piece of red litmus paper. After acidifying the solution with sulphuric or phosphoric acid, it is distilled (by means of introducing steam) until the distillate is no longer acid. The distillate, often measuring a litre, is titrated with 2 soda, using litmus as indicator.The alcohol is then calculated from the amount of acid found, and it must then be re-calculated to the original volume of the distillate. To make sure the distillate really contained acetic acid, the neutralised fluid is boiled down to a small bulk. An aliquot part is tested with barium chloride, and should there be any precipitate, it must be collected and allowed for. Another portion is mixed with a few drops of alcohol and then with sulphuric acid in excess. If after twenty-four hours there is a strong odour of acetic ether, the presence of acetic acid, therefore the presence of alcohol is proved beyond doubt. I must, however, point out the absolute necessity of thoroughly boiling the oxidised mixture with potash, otherwise the process is bound to fail.The amines always pass into the alcoholic distillate, even if distilled from an acid solution. They are not acted upon by the oxidising mixture, and, therefore, unless removed by boiling with caustic potash, they would again get into the acetic distillate. As already stated, not much importance seems to be attached to the qualitative and quantitative toxicological determination of alcohol ; not so much because there were no reliable processes, but principally because it is only reckoned a poison in its pure state. I hold, however, a quite different opinion. Think how alcohol in its various forms, from brandy to methylated spirits, is within almost everybody's reach, and how easily it may be abused ; not so much in the case of grown-up people, but helpless infants. Is it not a well-known fact, that gin, for instance, is largely administered to infants to make them sleep, and how many have not in this way been killed by their unnatural mothers, without these in the least being suspected Are not two tablespoonfuls of corn brandy often a fatal dose for a child of six months old? Is it not probable that among the lower classes this comparative safe way of infant poisoning is largely practised ? The chemical detection of alcohol is beset with difficulties ; then first of all it rapidly passes out of the system, and it has also been proved that traces are actually formed in the living organism, whilst it is even a product of putrefaction. I therefore must inaist upon the quantitative estimation of the spirit, which, if the amount should be excessive, will point to the use of alcoholic liquors, or even tinctures, or may be in other respects a valuable clue. (To be continued.) 10 Or we may apply Carstanger's well-known cacodyl test. The principles of the method just described will be easily understood.

ISSN:0003-2654    

DOI:10.1039/AN8901500069

出版商:RSC    

年代:1890

数据来源: RSC

摘要:

74 THE ANALYST. ON A VOLUMETRIC METHOD OF GENERAL APPLICABILITY FOR THE DETERMINATlON OF COMBINED SULPHURIC ACID." BY LAUNCELOT W. ANDREWS. OF the volumetric methods at present in use for the determination of sulphuric acid, none can be considered entirely satisfactory, although some of them are very useful for technical purposes, Several of these methods involve a double titration, some require three standard solutions, and others are only applicable in the absence of bases precipi- table by sodium carbonate. The author believes, therefore, that the presentation of a new method, applicable in the presence of magnesium, calcium, aluminum, zinc, manganese, iron (ferric), nickel, cobalt, and silver, which requires but one standard solution with a single titration, and which in precision is a t least equal to the ordinary gravimetric determination as barium sulphate, while demanding much less time for its execution, will not be thought super- fluous.The process depends upon the following series of reactions : First, t o the solution of a sulphate is added an excess of a solution of barium chromate in hydrochloric acid ; second, the solution is neutralised with ammonia or calcium carbonate, and filtered ; third, the filtrate is acidified with hydrochloric acid, potassium iodide added, and the free iodine titrate with decinormal sodium thiosulphate solution (1 C.C. = 12,654 mg. iodine = 3.662 mg. SO,). The barium chromate employed may contain bsrium sulphate, but must be com- pletely freed from soluble chromates and from barium carbonate, nitrate or chloride, by prolonged washing, first with boiling water slightly acidified with acetic acid, finally with hot distilled water, until the washings give no precipitate with sulphuric acid, and (in a quantity of 100 c.c.) a barely prcaeptible reaction with hydrochloric acid, potassium iodide and starch paste.? A suitable solution of the barium chromate is propared by digesting it with hydro- chloric acid containing 36 grms.acid in the litre. This solution will contain from 2 to 4 per cent. of barium chromate, according to the temperature at which it was prepared. The reagent being ready, the analysis is performed as follows : - The sulphate to be determined is diluted, if necessary, until it does not contain more than 2 per cent, at most, of sulphuric anhydride, is made approximately neutral, and is heated to boiling.While boiling hot, an excess of the barium chromate solution is gradually introduced, and the boiling continued one minute, or longer, if carbonates were present. The precipitate of barium sulphate is always yellow from the barium chromate which is carried down with it, provided sufficient excess of the latter reagent was added. ~ ~~ ~ ~ * American L'r'Lemicnl Journal. t When ba,rium chloride is precipitated with an excess of potassium chromate, the water with which the precipitate is mashed will, for a long time, show a yellow colour. This is not, as has been supposed, due to the solubility of RaCr04, but to the fact that it obstinately retains soluble chromate, According to the author's observation, barium chromate is not sufficiently soluble in water to impart any colour t o the latter. According to the mean of four concsrdant determinations, one million parts of water dissolve 15 parts barium chromate a t 1S0 C.THE ANALYST.75 Calcium carbonate, which must be entirely free fro= barium or strontium cnbonates or calcium sulphate, is then thrown in small portions into the still hot liquid until no further evolution of carbonic anhydride is observed, and the b d i n g continued one or two minutes. The solution is filtered while hot, and the precipitate is washed with a small quantity of hot water until the washings are colourless, and a little longer. Under these conditions, the barium chromate hasno tendency to run through the filter or t o retain any soluble chromate. 75 C.C.of water will usually be found more than suffizient to effect the washing. If, on the other hand, the solution is allowed to stand over night with the pre- cipitate in it, calcium chromate will be retained and a longer washing becomes necessary. In this case the results may come somewhat too high, in consequence of the necessarily large amount of wash-water dissolving an appreciable quantity of barium chromate. Under normal conditions the error from this source is quite insignificant. The filtrate, after cooling, is treated with a sufficient amount of crystals of potassium iodide (free from iodate) and with 5 to 7 C.C. fuming hydrochloric acid for each 100 C.C. of liquid. This amount of acid is enough to induce a prompt and complete reduction of the chromate, but not enough to decompose the starch paste.It is advis- able to run in the decinormal sodium thiosulphate from a burette until the brown colour OF the iodine is nearly discharged before adding the starch, and then to continue the titration slowly, with constant stirring, until the turning point is reached. The above process must be modifiad in the presence of ferric, nickel, or zinc salts by using ammonia instead of calcium carbonate to neutralisa the acid liquid. The solution in this case is to be made distinctly alkaline, and the excess of ammonia boiled nearly away before filtering. The necessity for this modification arises from the fact that if a ferric or nickel or zinc salt is boiled with a chromate and calcium carbonate, basic chromates of iron *and nickel are precipitated, from which the chromic acid cannot be removed, or only with difficulty, by washing.Barium chromate, when pre- cipitated from its acid solution by ammonia, does not possess the agreeable properties which it shows when thrown down by calcium carbonate. It is much more finally divided thanin the latter case, tends t o run through the tllter, which must therefore be double or of very dense paper, and requires a longer washing to remove the soluble chromates which it more tenaciously retains; consequently, ammonia is only to be used when the employment of calcium carbonate is inadmissible. It is not practicable to precipitate the excess of barium chromate with sodium acetate from hydrochloric acid solution. Numerous experiments, the details of which it is not worth while to give, show that barium chromate is so eoluble in hot dilute acetic acid that the results fall 3 to 5 per cent too higb, while if precipitated cold and allowed to stand, the results are too low.* The following analyses show the applicability of the method :- I.Taken 10 C.C. of a solution containing 20*8984 grams. pure and dry ammonium Diluted to 50 c.c., treated with 15 C.C. BaCr04 solution with CaCO,, sulphate per litre. as described above. *The method cannot be used in the presence oE phosphoric anid, and, of course, all reduoing agents, it6 well as bismuth and copper salts, must be excluded.76 THE ANALYST. Required 47.60 C.C. :o Na,S,Oy sol.=*1267 gram. SO, found. Calculated, -1366 gram. SO8 ; 100.08 per cent.found. 11. Taken 10 C.C. of the same ammonium sulphate solution and treated as in No. I, The volume of the solution before titration was 300 C.C. 111. 20 C.C. of the same ammonium sulphate solution, treated as before, required Total volume of the solution, 400 C.C. ; 100.37 per cent-found. IV. Taken -2980 gram. CuSO, + 5H20, small crystals obtained by triple recrystal- lisation of a commercial sample. The copper was precipitated from boiling sol. with (NH,),S (free from sulphate), solution boiled with acetic acid to expel H,S, filtered and filtrate treated as above. 35-95 C.C. Na,S,O, sol. required = 00957 gram. SO, = 32.11 per cent, found. Theoretical par cent. = 32.09. V. Taken 10 C.C. (NH4)2S04 solution (see 1) containing *20898 gram., diluted to 100 c.c., treated with 20 c.c, BaCrO, sol.ars above and neutralised with ammonia, Re- quired 47*30 cc. :o Na,S,O, sol. = 01260 gram. SO3 instead of *1266 gram. Found 99.52 per cent. Treated as No. V. Required 80.66 C.C. :o Na,S,O sol. = 9147 gram. SO,. Found 33.11 per cent. SO,. VIL a. Taken 100 C.C. of the Iowa City watersupply. Treated as No. V. Required 2.10 C.C. ;o Na,S,O,. sol. 6, Taken 200 C.C. ditto, ditto. Found 56 mg. and 57 mg. SO, per litre. A gravimetric analysis gave 58 mg. SO, per litre. It seems probable that an indirect determination of sodium and potassium would be possible by weighing these elements as sulphates and determining the sulphuric anhydride volumetrically as described. If feasible, it is evident that it would often be more convenient than the usual indirect determina- tion as chlorides, while free from some of the well-known sources of error involved in the gravimetric determination of sulphuric acid in the presence of alkalies. It is both a duty and a pleasure for me to take this opportunity to express publicly my thanks to Mr. F. W. Spanutius, instructor in chemistry here, for the zeal and skill with which he has assisted me in the experimental part of this investigation. Some of the test analyses given above were performed by him. Required 47.60 C.C. :,, Na,S20, sol. 100*08 per cent, found. 95.50 C.C. to Na2S20, sol. VI. Taken 06485 gram. (NH,),Fe,(SO,), + 24H,O. Calculated -2153 gram. SO,. Theory 33.20 per cent. Required 4.30 cc. :o NasSsOs sol. Experiments to test this are now in progress.

ISSN:0003-2654    

DOI:10.1039/AN8901500074

出版商:RSC    

年代:1890

数据来源: RSC

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76 THE ANALYST. ELECTROLYTIC SEYARATlONS. BY EDGAR F. SMITH AND LEE K. FRANKEL. (Read at the December Meeting of the Chemical Section of the Pra&%ie Institute.) THE study of the electrolysis of the double cyanides of cadmium, copper and zinc, enabled us to formulate conditions, by which the separations of cadmium from zinc (American Chemical Journal, 11, 352) and cadmium from copper (Journal of Analytical Chemistry, 3, 385) were possible, and in every particular satisfactory.THE ANALYST. 77 The ease with which cadmium was separated from zinc, and the very close results obtained with these metals, led us to apply the method to the separation of cadmium from cobalt and from nickel. Operating first with cadmium alone, we dissolved sufficient pure sulphate in water, so that 10 C.C.of the solution would contain 0.1688 grams. metallic cadmium. To this volume (10 c c.) were added lour and one-half grams. pure potassium cyanide, and the solution made up to 200 C.C. with water. A current yielding 0.4 C.C. 0-H gas per minute was allowed to act upon the same for a period of fourteen hours. The deposited metal weighed 0.1686 gram., a difference OF- 0.11 per cent. from the theoretical. A second trial, wikh conditions precisely analogous to those just mentioned, gave 0,1690 gram. cadmium, a difference of + 0.11 per cent. from the theorctical. CADMI U’X FROM COBALT. In the third experiment the conditions were the same as before, with this difference, that an equal amount of cobalt was also present in the solution. The result of the electrplysis was 0.1689 gram.cadmium, a difference of + 0.05 per cent. from the required. The fourth experiment, similar in every way to the third, yielded 0.1689 gram. cadmium, a difference of f0.05 per cent. from the theoretical. The cadmium was fully deposited on both occasions, and contained no cobalt. Pasking to the separation of cadmium from nickel, the results were so surprising CADMIUM FROM NICKEL. that we give the same in detail, although negative in character. 1 2 3 4 5 6 ‘7 8 9 10 11 Cadmium pre- sent, in grams. Nickel present. 100 per cf. 7 7 7 7 7 ) 7 *, - $5 per ct. 50 per ct. 25 per ct. 7 7 Potassium Cyanide, in grams. -- 4$ ? 7 9 7 7 7 7 7 7 7 7 7 7 7 ) 7 7 Tot a1 Dilution. 200 C.C. 7 7 7 7 7 7 7 9 9 7 > 7 > > 7 7 7 ) 7 7 Strength of current in C.C. 0-H gas per minute.0-3 C.C. 7 7 7 7 7 7 7 ) 7, 0.5 C.C. 0.15 C.C. 0.5 C.C. 0-15 C.C. 7 7 Cadmium found. 0.1717 0.1702 0.1725 0-1750 0.1 72 1 0.1737 0,1827 0.1923 0.1841 0.1882 0.1 854 The period of time during which the current acted in each of the above experi- inents was sixteen hours. Nickel was always found in the cadmium deposit, while in many cases the precipitation of the cadmium was incomplete. The conditions were varied, yet the results were wholly unsatisfactory. By gretttly increasing the quantity of cyanide, we discovered that the cadmium precipitation was retarded. Nickel when alone, and when under the conditions given above, would not deposit with the strength of current used by us. This behaviour is only another indication that if we would7s THE ANALYST. 0.3 C.C.0.25 C.C. 7 7 make electrolytic methods widely applicable, it is first necessary to extend the study of the action of the current to all the salts possible, and to investigate carefully the in- fluence of each metal upon its associates under varying conditions. From what we have thus far accomplished, we find the electrolytic separation of cadmium from copper, from zinc, and from cobalt, in cyanide solution, all that could be expected from any method. The cadmium deposits, in the experiments recmded in this paper, were always washed with boiling water ; the drying was done upon the edge of a warm iron plate. We have already called attention (dmericccn CJzenzicaZ Joumaal, 11, 264) to the fact that mercury is fully precipitated from the solution of its double cyanide by a compara- tively feeble current, and that the separation of this metal from copper is possible so long as the quantity of the latter does not exceed twenty per cent.of the mercury present. More recently we have execnted a series of experimmts looking to the separation of mercury from zinc, nickel, and cobalt. IvIERCURY FROM ZIFC. The results with these metals are :- 0.li17 0-1715 0.1706 2 1 I 0 . y 7 7 100 per ct. 7 7 ) - I 200 C.C. ~ 44 1 ? ? ? 7 - 100 per ct. 1 7 7 , :, ,, 7 7 3 3 4i + 0.12 per cect. - 0.52 per cent.. - 0.34 per cent. The time in each deposition was sixteen hours. From these figures the separation is possible. I n the following experiments it will be observed that the error is much less, and accordingly makes t.he method trust- worthy and, from its accuracy, well suited for scientific as well as technical work :- Mercury was not found with the zinc. 0.2440 - I- 7 7 7 7 7 7 I j; 1- ____- I 200 C.C. ! I I: 3: i 4 s ZCI %' G u 1 0.2435 1 0.2445 1 0.2441 0.244 5 0.2431 0.245 4 - 0.20 per cent. +0.20 ,) +0-04 ?, +0.20 ,, + 0 * 3 i 7 7 +0*50 ,, The time of precipitation, made a t the ordinary temperature, amounted to sixteen The mercury deposit was washed with hot water, and dried upon a moderately hours. warm iron plate. (To be continued.)

ISSN:0003-2654    

DOI:10.1039/AN8901500076

出版商:RSC    

年代:1890

数据来源: RSC

摘要:

THE ANALYST. 79 REPORT OF RECENT RESEARCHES AND IMPROVEMENTS IN ANALYTICAL PROCESSES. ESTIMATION OF URIC ACID BY SODIUM HYPOBROMITE. M. BAYRAC (Compt. rend,, 17 Feb., 1890).-50 C.C. of the urine are evaporated on the water-bath. The residue is treated with 5 to 10 C.C. of diluted hydrochloric acid (1 in 5), and the precipitate is washed with alcohol to remove urea and creatinine. It is then dissolved on the water- bath with 20 drops of solution of sodium hydrate. and heated to nearly boiling with 15 C.C. of saturated solution of sodium hypobromite in the usual apparatus for urea, estimations. The whole process can be performed under two hours. M. S, A,. M. THE FERRIC CHLORIDE TEST FOR COCAINE. PROF. PLUGGE (Ned. Tydschr. v. Pharmacie, etc., March, 1890).--Nessrs. Lerch and Scharges have lately published a delicate test for this alkaloid.A drop of very weak ferric chloride is added, and the mixture heated to boiling. A blood-red colour is developed, almost resembling ferric sulphocyanide. And apparently nothing is more natural. Does not cocaine on boiling with water decompose into ecgonine, methylic alcohol, and belzxoic acid Z And does not this acid give a red (2) colour with ferric chloride. How scientific this may all seem, the author found, however, that the same coiour may be just as readily got by applying the test without cocaine, for reasons which any one acquainted with the chemistry of iron salts will readily understand, L. DE K. NEW TEST FOR CONINE. VAN SENUS (Ned. Tydschr. v. Pharmacie, etc., March, 1890).-This alkaloid gives a fine blue, changing to red and yellow when mixed with nitro-benzol.The test is, however, not successful with the pure C,H,NO,, but only with the article prepared by acting with nitric acid on commercial benzol. When such nitro-benzol is distilled, the first fractions give the reactions but very imperfectly, but the residue left in the retort produces a fine display of colours. The author soon hopes to be able to find out to what substance the reaction is really due. Not unlikely it may be caused by the presence of carbonic Aniline and nicotine do not give the reaction. sulphide in the crude benzol. L. DE K. ADULTERATION OF LINSEED OIL. PROF. WEFERS EETTINK (Ned. Tydschr, ZI. Pharmacie, etc., March, 1890).-A sample submitted to the author, although conforming to the standards of purity as a t present laid down, was, howeyer, perfectly useless for painting purposes, as when mixed with white lead this became brittle in a few hours.This pointed to a largo amount of free acid, which induced the author to apply the process of Salskowski, viz., dissolving in ether-alcohol and titurating with - alcoholic potash. To 10 ascertain the nature of the acid, a large quantity of the oil was agitated with a 10 per cent. solution of common soda. After the greater part of the oil had separated it was agitated with petroleum spirit to free it from oily matter, and then decomposed with acid. The fatty acids thus separated gave a I. absorption of 146. (No doubt this figure would have been higher still if any stearic acid had been first removed.) The author hesi- tates to call it liaoleic acid, but feels pretty sure it has been wilfully added.L. DE K. 9% Thirty-four per cent. of free (oleic) acid was thus found.80 THE ANALYST. ESTIMATION OF FREE ACID IN SOLUTIONS OF STANNOUS CHLORIDE. w. MINOR (Zdschr. f. angew Chemie, No. l).-The estimation of hydrochloric aoid in solutions of stannous chloride cannot be done with silver nitrate, as insoluble stannio hydrate would be formed as well m silver chloride. The author recommends the following process :- 10 C.C. of the fluid are diluted with hot water, and hydrogen sulphide is passed until all the tin is precipitated. The liquid is filtered off from the precipitated stannous sulphide in a litre flask. After making up the contents to the mark, 500 c.c.(= 5 C.C. original fluid) are boiled for a ahort time to expel the hydrogen sulphide, and finally titrated with normal soda. This will give both free and combined hydrochloric acid. The amount of combined aoid may of course be readily calculated from the amount of stannous tin, which the author prefers to estimate with iodine. If the sp. gr. of the fluid is known, the amount of acid by weight can be readily calculated. L. DE K. ARTIFICIAL COFFEE IN GERMANY. R. WOLFFENSTEIN (Zeitschr. f. angew Chemie, No. 3, 1890).-The author analysed two varieties, known in Germany as Domkaffee and Allerweltskaffee. The complete absence of caffeine undoubtedly proved the absence of coffee. The microscope showed the first article to practically consist of chicory, whilst the other one contained large quantities of lupines. The author also succeeded in isolating a brown colouring matter, possessed of the same properties as the well-known Casseler-brown. It not only behaved spectroscopically the same, but also in its chemical reactions. Although soluble in alkalies and in water, it is completely precipitated by addition of mineral acids, such as hydrochloric acid. 14 grms. of the sample were extracted with water and precipitated with hydrochloric acid, which yielded 1.6'7 grm. of colouring matter, which corresponds with 11.9 per cent. adulteration.

ISSN:0003-2654    

DOI:10.1039/AN8901500079

出版商:RSC    

年代:1890

数据来源: RSC

摘要:

80 THE ANALYST. REVIEWS. CHEMICAL LABORATORY LABELS ; COMPILED BY w. H. SYMONS, E".c.s., F.1.C. Second THIS is a collection of labels for large bottles, supplementary to Parts I. and 11. already published, which latter are for smaller bottles. The labels are well printed, well selected, and really cheap, there being 250 in this book for IS. 6d. Tables for conversion of thermometric and barometric degrees, and for the pressure of aqueous vapour are also included, ready for sticking up in any convenient place. All Mr. Symons' volumetrio labels are very well done, with a full list of equivalents on each, and his collections are certainly the best in the market a t the moment for the praciising analyst, CATALOGUE OF SCIENTIFIC APPARATUS AND CHEMICALS; BY J. ORME AND co., 65, MESSRS. ORME have just issued a very complete and well-illustrated catalogue of chemical and physical apparatus and chemicals, a special feature of which is the consideration of all articles for photography. The prices are reasonable, and the book should add to the businem done by the firm, as well as being convenient for reference by its possessors. Edition, Part 111. Barbican, E.C.

ISSN:0003-2654    

DOI:10.1039/AN8901500080

出版商:RSC    

年代:1890

数据来源: RSC