摘要:

THE INFLUENCE OF TEMPERATURE AND CONCENTRATION ON THE SALINE CONSTITUENTS OF BOILER WATER. BY CECIL H. CRIBB B.Sc. F.I.C. (Rend cit the Neeting A p d 4 1900.) THE behaviour of the saline constituents of water when used in high-pressure boilers has as far as I am aware never formed the subject of a paper before this society. The matter has only a remote connection with analytical work but to all who are likely to be consulted on questions relating to boiler waters it should be of interest. Personally I have not unfrequently been asked by engineers what would happen to a water when heated in a boiler working at a certain pressure or what proportion of its dissolved salts it would deposit. On looking through the literature of the subject I was surprised to find how little really definite information was to be had.The common use of high-pressure feed-water heaters shows that the effect of pressure i.c. temperature on the solubility of the salts is fully recognised and take 170 THE ANALYST. advantage o f ; but I know of no systematic investigation such as would enable one to predict with even approximate certainty the changes in composition that would be brought about when a water is heated above 100" C. or the further changes due to the concentration which necessarily occurs in a boiler working under the ordinary conditions. Again as analysts we are frequently called upon to say whether judging from analysis a water will or will not have any action on the boiler or its fittings. I n most cases the problem is a fairly simple one but in some instances a little knowledge as to what a water is likely to become after concentration to from five to twenty times its original strength might be of considerable use.Even with the best of boiler waters a certain amount of corrosion takes place and it is not unreasonable to suppose that in this c,onnection the concentration is not without influence. In any case the high temperatures have a marked effect on the chemical activity of those constituents to which corrosion is usually attributed. The problems to be dealt with are somewhat complicated because it is impossible, with steam-boilers working under ordinary conditions to separate the influence of pressure from that of temperature and these again from that of the concentration of the more soluble constituents.The effects of all three are moreover obscured by the constant addition of fresh feed water diluting the boiler contents and at the same time bringing with it fresh supplies of saline matters some of which add to the con-centration while others are speedily deposited because of the sudden increase of temperature to which they are exposed or because of the superabundance of certain salts in the surrounding medium. The various analyses under the heading '' Water from Boiler " (Tables I. III., IV. V. VI. and VIII.) show the sort of sampl'es that are obtained from boilers which have been running for various periods up to six or seven weeks. Of course in the rare instances in which pure sea-water is used in high-pressure boilers the degrees of salinity here shown are enormously exceeded but I have not been able hitherto to obtain any specimens of this sort for examination.I n Table I. is given the composition of a very bad feed water and of a sample taken from a water-tube boiler in which it had been used for some weeks. The analyses are far from complete but a brief glance at them will serve as an intro-duction to the more complicated series of analyses that follow. In this and all the other analyses of waters the results are expressed in parts per 100,000 : TABLE I. Feed Water. 301.5 145.5 Total hardness 95.2 Permanent hardness 54.4 Temporary hardness 40.8 Water from Concentration Boiler. Factor. 1,601-2 5.31 670.0 4.64 183.1 1.91 183.1 3.34 It will be seen at once that all the constituents have.become concentrated to a different extent. The numbers under the heading & ' Concentration Factor " were obtained by dividing the proportion of each constituent of the boiler water by that of the same constituent in the feed water and they really represent the number o THE ANALYST. 171 volumes of the feed water that would contain the same amount of that particular constituent as one volume of the boiler water. If owing to the evaporation taking place in the boiler all the constituents had been concentrated to a like extent all the concentration factors should be the same. They all as would be expected differ, and the question at once arises Which of them if any indicates the real degree of concentration? Or to put it in another way have any of the constituents merely gone on accumulating in the boiler ? or have they all suffered a certain amount of deposition in the solid form or have they been decomposed ? Obviously the extent to which any particular salt has gone out of solution owing either to deposition or decomposition can only be ascertained if the real degree of concentration is known.This can plainly only be got at indirectly but some means of doing it is absolutely essential so I propose to devote a short time to the discussion of the most suitable plan before proceeding further. I n a laboratory experiment the actual solid deposit could be collected weighed and analysed or the total amount of water actually used could be measured and compared with the volume of the residual water but obviously such methods are out of the question in the case of boilers working under ordinary conditions.If however one constituent can be found which never goes out of solution or leaves the water in the boiler owing to decomposition of any sort then that will serve as a direct measure of the concentration meking it possible if the capacity of the boiler is known to calculate the actual volume of water evaporated and consequently the amounts of each of the other Constituents which should remain in the concentrated water had they too suffered no loss. The chlorides the nitrates and the alkalies are on the whole the most likely to answer the purpose. The nitrates are however likely to become reduced either by organic matter or the metal of the boiler and the estimation of the alkalies is trouble-some and not too accurate so that one naturally turns to the chlorides.All the chlorides are so soluble in water that they are never likely to come out of solution from mere concentration alone except under the most extraordinary circumstances. Hence it is rare to find scales and deposits from land boilers containing any consider-able proportion of chlorine and as a rule that element is present only in minute traces. According to Vivian Lewes (‘( Service Chemistry,” p. 119) even sea-water when evaporated does not begin to deposit salt until about 24 per cent. of the latter is present in solution ; and the same author found an incrustation from sea-water to contain only 2.79 per cent. of sodium chloride. I n my own experience I have found this figure to be very much exceeded.Thus a scale from a naval water-tube boiler of recent construction in which owing to an accident much sea-water had to be used had the following composition showing that it consisted almost entirely of sodium chloride : TABLE 11. Per Cent. Fe,OJ . . . . 0-28 CaO . . . . . 0.19 . . . . . 1-40 . . . . . . . . . . . . 1-72 MgO so, c1 . . . . . . . . . . 58-49 OH,. . . . . . 0.8 172 THE ANALYST. No ordinary water is ever allowed to concentrate in a boiler to such an extent as to even approach sea-water in salinity so that the chances of the salt crystallizing out can be safely neglected. On the other hand the presenceof magnesium chloride has to be reckoned with. There seems to be a good deal of doubt judging from text-books as to the behaviour of this substance when heated.Some e.g. Bloxarn state definitely that solutions of magnesium chloride decompose on evaporation giving off hydrochloric acid. Comey’s ‘‘ Dictionary of Solubilities,” Watts’ ‘‘ Dictionary of Chemistry ” (Morley and Muir) and Blount and Bloxam’s ‘‘ Engineering Chemistry ” say practically the same while most of the other English text-books refer only to the behaviour of the solid substance. There is in any case a widespread impression amongst chemists that the solution is decomposed on heating at ordinary pressures. Those text-books that mention the decomposition of the solution plainly do not refer to evaporation under pressure and the original fountain-head of their informa-tion seems to be a paper by Casaseca (Comptes Rendus 1853 xxxvii.3501 who found that a solution of magnesium chloride when heated begins to decompose when it contains only six molecules of water to one of the chloride. From the way he conducted his experiment he was obviously igniting the ordinary crystalline form of the salt (MgCI,,GOH,). When a solution of magnesium chloride is evaporated on a water-bath I find that this salt with six molecules of water always remains behind and the evaporation may be repeated any number of times without any decomposition occurring the total solid residue remaining quite constant and always dissolving without difficulty to a clear solution. The proportions of chlorine and of magnesium also show no variation. If the salt be melted in its own water of crystallization but little visible decom-position takes place until a temperature of about 150” C.is reached and the thermometer rises slowly to about 180” C. There can be no doubt that the general impression as to the instability of solutions of magnesium chloride when heated is due to the misleading employment of the term “ evaporation ” in the text-books. I find further that a solution of niagnesium chloride so strong that it deposited crystals of the hydrated salt in the cold niay be distilled to further concentration without giving off a trace of acid. The same experiment repeated with the addition of a large quantity of iron filings to the solution gave a like result which seems to show that the metal of the boiler would be without influence in this connection.Vivian Lewes (“ Service Chemistry’’ p. 121) states that “ when sea-water is evaporated in contact with a large surface of metallic iron no chloride cart be detected in the distillate until four-fifths of the solution has distilled over.’’ Such a concentration of sea-water would not contain more than 2+ per cent. of MgCl, while the solution I employed was nearer 50 per cent. so that further investigation of the matter is required. The behaviour of magnesium chloride solutions when heated under pressure still remains to be considered. That the salt if present in the feed water, is almost entirely decomposed in the boiler is plain from the fact that all the analyses in the tables (IV. V. VI. and VIII.) show a remarkable disappearance of the MgO from the water after it has entered the boiler.Magnesium hydroxide is one of the commonest constituents of boiler incrustations while chlorine i TEE ANALYST. 173 any quantity is rare. This holds good even when there is much Mg and C1 in the feed water and is very strikingly shown by the analyses in Table III. in which the feed water contains very large proportions of both MgO and C1 while the scale is practically free from chlorine but contains nearly one-third of its weight of magnesia : TABLE 111. Feed Water. Scale from Boiler. Total solids . . 938.5 Chlorine (Cl) . . 460.0 Moisture trace Carbonic acid (CO,) . 13.38 0 per cent. Sulphuric acid (SO,) . 45-76 39.87 ,, Lime (CaO) . 117.88 28.00 $ 7 Magnesia (MgO)' '. . 129.84 30.14 ,, Nitric acid (N,O,) . 9.55 Insoluble 3.19 ,, The magnesium has therefore plainly left the water under the influence of the high temperature to which it has been exposed.What has happened to the chlorine? Unfortunately in this particular case I have no analysis of the water after it had been in the boiler but it by no means follows that because magnesium chloride is decomposed and its base deposited that the chlorine leaves the water at all. The process may be the result of a double decomposition with some other salts ; but even if free hydrochloric acid is formed it is far from certain that it would be evolved as gas and pass away with the steam. That it does not do so in the case of waters reasonably suited for steam-raising is clearly shown by Table IV. which gives the composition of the contents of a boiler using a London water after running for about six or seven weeks and that of the condensed water collected after the steam had passed through a superheater : TABLE IV.Lamashire Boiler 40 lb. presswe. Total solids , Chlorine . . Nitric acid (N,O,) Carbonic acid (GO,) Sulphuric acid (SO,) Silica (SiO,) . Oxide of iron (Fe,O,) Lime (CaO) . Magnesia (MgO) Water from Boiler. . . . . 503.2 . . 94.0 . . 2.65 . . 5.98 . . 127.68 . . 1.92 . 0.72 . . 18.24 . . . . 0.33 Condensed Steam. 2.60 0.21 0.016 0.14 0-49 0.20 0.16 0.65 0.15 In view of the concentration a good deal of magnesium must have been deposited in the form of sediment or scale and yet the condensed water shows no excess of chlorine but rather the reverse.I t is in fact obvious in the case of ordinary waters that no hydrochloric acid passes away in the steam as otherwise the engines would always be attacked. Further it has been recently shown by Bailey and Johnston ( J . S. C. I. 1899 p. 455) that an aqueous solution of hydrochloric acid does not give off any acid when distilled until the proportion of the latter reaches nearly 1 per cent 174 THE ANALYST. Of course under a high pressure something entirely different may happen. Table V. which relates to a water which contained a fair proportion of MgO and much chlorine and acted powerfully on the boiler and its fittings* affords an indirect proof that no appreciable amouni of chlorine leaves the boiler : Total solids Nitric acid (N,Oj) Chlorine (Cl) Sulphuric acid (SO:) Carbonic acid (CO,) Silica (SiO,) .Oxide of iron etc. Lime (CaO) . Magnesia (MgO) . Na,O and K,O . TABLE V. Pressure 140 Zb. Feed Water. . . . . 99.2 . . Trace . . 18.15 . 16.76 . . 15.21 . . 1.30 . . 0.40 . . . . 7-77 . . 3.33 . . 44.89 Water from Boiler. 411.0 Trace 93.5 84.8 38-94 7.0 209.9 Concentration Factor. 5.15 5.06 4.68 The water was strongly alkaline owing to the presence of sodium carbonate and it is not unreasonable to suppose that the lime and magnesia which are completely absent from the water after heating were deposited in the form of carbonates. I n the absence of lime and magnesia there is no more reason for the SO leaving the water in the boiler than for the mixed alkalies or the chlorine consequently the concen-tration factors for these three should be identical within the limits of experimental error.I n any case, the figure for the C1 is the highest as indeed it almost invariably is throughout the tables. I n this particular analysis at all events the amount of chlorine is almost certainly a true measure of the concentration; in the others it is if not the true one, at any rate the best available. In the present connection as well as from a theoretical standpoint the behaviour of magnesium chloride when its solutions are heated under pressure is of such great interest that I have commenced its investigation and hope to publish the results elsewhere. I may say briefly that under a pressure of one atmosphere (temperature about 125' C.) practically nothing happens to a solution containing 2-25 per cent.of MgCl, but at five atmospheres a solution of the same strength is partially decomposed with deposition of MgO and evolution of HCl the extent of the decomposition being determined by the duration of the experiment and the freedom with which the steam is allowed to escape. Working with the pure salt however, the conditions are entirely different to those which obtain in a boiler in which a water containing a mixture of many salts is being evaporated and the large surface of iron exposed to the liquid may profoundly affect the result. I n any case I propose to assume in the absence of satisfactory evidence to the contrary that in the case of the waters referred to in Tables IV.V, VI. and VIII. the chlorine is a sufficiently exact measure of the concentration to render it possible 80 pounds gave no trouble. This is the case with two of them and the third is not far out. * This boiler worked at 140 pounds pressure ; other boilers with the same water working a THE ANALYST. 175 to calculate the original volume of feed water used. The use I propose to make of the concentration factor obtained in this way will appear later. Table X. (p. 181) shows the composition apart from the alkalies oxide of iron, and silica etc. of four waters (1) New Kiver water; (2) water from a boiler for which it was used after working 62 hours at from 70 to 80 pounds pressure ; (3) after working 468 hours at the same pressure ; and the same water evaporated at a pressure of only 6 ounces per square inch till the chlorine contents reached that in No.3. Table VI. deals with a still more extended series of samples for which I am indebted to Messrs. W. H. Allen Son and Co. of Bedford. The details as to the samples are stated in the tables ; the intervals ah which the samples were taken are complete days whereas in Table X. they are hours of actual working. To get some idea of the effect of concentration alone Table VI. may be studied in more detail. TABLE VI. Bedjonl water 180 poz~?zds pressure ; boilel. cuporates 3,000 gallons in 10 bows ; snm&s collected at iiztervals of 1 8 and 24 dc~ys from date of lightiTzy zcp. From Hot Well. Total solid matter . 33.0 Carbonic acid (CO,) 1.27 Sulphuric acid (SO,) 11.36 Magnesia (MgO) .1.35 Chlorine (Cl) *.* 2.85 Lime (CaO) . . 7.35 After 1 Day. 106.12 14-95 0.97 41.02 8.00 2-77 After 7 Days. 41.15 1.22 49.58 5.34 0.47 171.0 After 24 Days. 341.7 90.0 3.50 82.52 9.20 0 As would of course be expected the water at the end of twenty-four days has become highly concentrated but the results differ for each constituent. Thus while the total solids in twenty-four days has reached ten times its initial aiiiount the concentration of the carbonic anhydride is only 3 times that of the chlorine 30 times the sulphuric acid 7 times the lime 1.2 and the magnesia has disappeared altogether. Of course any coinparison between the feed-water and any of the other samples necessarily takes into account the influence of the high pressure and temperature to which the latter have been exposed.But if any one constituent is taken and the effect of time alone is studied the figures still require a good deal of interpretation. Thus the chlorine is 5 times as great after working one day as it was before entering the boiler but six further days’ work only produce 3 times the effect of the one day and twenty-three days’ more only 6 times. The SO, again is 3 times as great after one day 4.3 times after seven days and only 7 times after twenty-four days. A very little reflection will however be enough to explain some of these seeming contradictions. Thus the apparent effect of the initial day of working will always be greater than that of any subsequent one (as far at all events as the GOa SO,, lime and magnesia are concerned) because the boiler is started with its contents undiluted with condensed water from the engine.That the changes produced in a unit of time should decrease as the concentration increases is what would naturally be expected in view of the fact that the solid matter entering the boiler with the feed water must bear a steadily decreasing ratio I n fact of all the constituents estimated not two behave alike 176 THE ANALYST. to the ever-growing amount of dissolved matter already there. The ratio will of course be partly dependent on the proportion existing between the evaporative power and the capacity at working level of the boiler-a proportion which varies very widely in the different types of boiler. That the individual constituents differ from one another in the extent to which they have become concentrated is of course owing to the greater insolubility of some of them at high temperatures or to their insolubility in strong solutions of the other saline constituents of which by far the most important in this as in the majority of waters is the sodium chloride.Further changes may also be produced by double decompositions giving rise to less soluble compounds. A very cursory inspection is sufficient to show that there is a continual falling out of solution of the majority of the salts but the full extent of this is marked by the mere accumulation of what remains. To get any idea of how much has gone out of solution it is necessary to consider the amount of feed water that the contents of the boiler at any time represent i e .to know the true concentration factor. I have alrea.dy given reasons for assuming that the chlorine is the best guide to this. On this assumption it is only necessary to divide the chlorine in the boiler water at any period by the chlorine in the feed water to find out how many volumes of the latter one volume of the water in the boiler represents this figure being of course, the true concentration factor. If this figure in turn be divided into the amount of any constituent it will give the proportion of that constituent still remaining dissolved in the boiler water expressed in parts per 100,000 of the f e e d water. Thus taking the chlorine in Table VI. the amount after one day viz. 14.95, divided by 2.85 (the amount in the feed water) gives 5.2; this is the concentration factor and indicates that the water after one day in the boiler contains C1 belonging to 5.2 times its volume of feed water and if the assumption already referred to be correct not only the chlorine but each of the other constituents as well unless the actual amount has been reduced by the particular consituent leaving the water owing to deposition as scale or sludge or by evolution in the gaseous form.If 5.2 be now divided into 14.95 the amount of C1 belonging to one volume of feed water is obtained, i.e. 2.85 the same as in the feed water because according to the initial assumption, no chlorine is lost. If 5.2 be divided into the other figures for the same period of working the results differ from the proportions of the same constituent in the feed water because all the constituents other than the chlorine have suffered loss either by deposition as sediment or scale or by evolution as gas.TABLE VII. After corn2eizsating f o r Water euapomtcd. Total solid matter Chlorine . . Carbonic acid . Sulphuric acid . . . Lime . . . . Magnesia . From Hot Well. 33.0 2-85 _. 1.27 11.36 ,. 7.35 1-35 After After i Day. 7 Days. 20.23 11-84 2.S5 2.85 0.184 0.085 7.82 3.43 1.525 0.396 0.528 0.032 After 24 Days. 10.56 2.85 0.108 2.55 0.285 THE ANALYST. 177 Table VII. is obtained in this way viz. by dividing the respective concentration factors for each sample calculated from the chlorine into all the other figures for the same sample.The effect is practically to restore the water that has been evaporated thus doing away with the merely cumulative effect of the concentration, and laying bare the combined effect of the high pressure and temperature and of the increasing salinity on the solubility of the various salts. The total solid matter obviously suffers from any changes that affect its con-stituents. I n Table VI. it has increased to about ten times its original amount but Table VII. shows that as long as the experiment lasted solid matters continued to leave the water and at the end of the twenty-four days 33.0 - 10.56 = 22.44 parts of solid matter per 100,000 of feed water used had actually disappeared. The carbonic acid owing to the use of a hot well and of condensed water is very small in the feed water and the subsequent differences in Table V.hardly exceed the ordinary error of experiment except in the case of the last. This sudden in-crease 1 am not prepared to explain. I t may mean that calcium carbonate is more soluble in the presence of much sodiuiii chloride or it may be the result of some double decomposition between the already deposited carbonate and the salts in solution. The sulphuric acid in Table VI. steadily increases but with no apparent relation to the time. Table VIL shows that there has been a steady and continuous loss of SO from the solution. The lime to which with the magnesia the greatest interest attaches is apparently slightly more after one day in the boiler than in the feed water ; but when allowance is made for the concentration it is apparent (Table VII.) that that constituent has suffered more heavily than all the others only one-fifth of the total amount present in the feed water remaining at the end of one day.The temptation to speculate as to its fate is very great and I much regret that the analyses are not complete. They were made some time ago when I did not realize the importance that might attach to the alkalies The amounts of lime that have vanished calculated from Table VII. seem to bear no regular relation to the C02 and SO which have disappeared and it seems probable that double decompositions between the scale and sediment and the dissolved salts are constantly occurring. I n any case it would be unjustifiable to base any theories on such a small number of analyses.As there is always far more than an equivalent amount of SO, it is fair to regard the lime left at the end of twenty-four days as being all present as sulphate ; the aniount found viz. 9.20 is equivalent to 22.34 parts of calcium sulphate. Tilden and Shenstone (Phil. Trans. part I 1884 p. 23) found that 100,000 of pure water at a temperature which gave a pressure of 132 pounds per square inch held in solution 27.0 parts of calcium sulphate and at 513.5 pounds only 18.0 parts, and calculating from these figures I find that at 180 pounds 26 parts per 100,000 should remain in solution so that it seems probable that the point of saturation for calcium sulphate at this temperature had been reached. Tilden and Shenstone’s figures were obtained with pure water so that it is plain that the concentration of the salts in the boiler water has not materially affected the solubility of the calcium sulphate.In Table X. column 3 however although the concentration has not been I n any case the difference is not very great 178 TEE ANALYST. carried nearly as far the sulphate of lime calculated from the CaO cannot exceed and is almost certainly less than 42.6 parts per 100,000 whereas Tilden and Shenstone found 56 parts to be soluble at that pressure. Here therefore it is quite plain that the saturation-point for SO pounds pressure is not nearly reached and yet it is obvious from Table XI. that SO in some form has been continuously deposited since the boiler commenced to work. So too in Table IV.the lime is equivalent to 44.29 parts of calcium sulphate while according to Tilden about 53 parts should be soluble. The magnesium exhibits similar peculiarities of behaviour to the lime but it is very interesting to note that at the end of twenty-four days it has absolutely disappeared. Although in Table VI. the quantity shows an increase at the end of one day, Table VII. makes it plain that a continual deposition of MgO in some form went on throughout the whole period dealt with. I n Table IV. which deals with a longer period the MgO also nearly but not quite vanishes ; and also in Table X. I n Table V. the disappearance is absolute owing no doubt to the large proportiOD of alkaline carbonates present. So far the tables have dealt with cases in which the pressure remained constant while evaporation went on.Through the kindness of Messrs. Marshall and Co. of Gainsborough I was enabled to obtain samples from a boiler in which the reverse conditions obtained-i.e. the pressure varied and loss by evaporation was as far as possible avoided thus affording an opportunity of studying the effect of pressure and the resulting high temperature comparatively free from the disturbing influence of the concentration. It is of course impossible in the case of steam boilers to separate the eEect of pressure from that of temperature as the one is the necessary concomitant of the other. But though water is commonly regarded as incompressible the effects of pressure upon its volume are quite enough to produce important and far-reaching consequences by depressing the level of the ocean (Tait Challenger Reports ( ( Physics and Chemistry,” vii.).The pressures referred to here are however infinitely greater than anything occurring in boilers. I t is I believe generally admitted that hydraulic engineers are not troubled in any way by chemical changes in the water constituents brought about by the highest pressures they employ. Nevertheless the possibility of the pressure itself playing some part in the changes taking place in the boiler contents must not be entirely disregarded although everything seems to show that it can only be slight. From a purely scientific point of view the effect of pressure has been studied by Bunsen ( A m . d. Clzo?n. ZL. Phaw~. 1848 76-85) who obtained entirely negative results.Sorby (PTOC. Roy. SOC. xii. 54) pointed out that Bunsen had failed to allow enough time for the effects to manifest themselves and showed by sealing up various substances in tubes which were completely filled with the cooled solution and warming them that chemical changes followed by increase of volume are resisted, and those resulting in a decrease of volume are promoted by pressure. Similarly To return to Tables VI. and VII THE BNALY ST. I79 with solution substances which expanded on entering into solution became less soluble under pressure and substances which contracted became more soluble. The vast majority of substances contract and thereEore pressure increases their solubility. The pressures he employed were however from 100 to 200 atmospheres but even then the efiects were extremely minute ; for instance the solubility of sodium chloride was only increased to the extent of 0.419 per cent.by a pressure of 100 atmospheres, that of potassium sulphate to the extent of 2.914 per cent. Spring, of LiAge (Zeit. fiir Yhysik. 'ZL. Chenz. 18S9) found that when a diminution of volume accompanies solution the presence of water facilitates the solidification of powders by pressure; and it seems extremely probable that in this direction if at all the pressure apart from the temperature affects the behaviour of the salts in boiler waters. There is one important difference between the conditions which obtain in a boiler and those under which all the above investigations were made-namely that in the former case steam in large quantity is continuously leaving the boiler and is free to carry with it any gaseous products that may be formed.The experiments of Tilden and Shenstone have already been referred to. TABLE vm. Gainsborough IVatw heated q i j ? a i d kept f o r ten minutes at 1wesswe of 50 lb., Steam kept CIS fur as possible 100 Zb. 150 Ib. 200 Zb. cincl 250 16. per S ~ I L C I Y ~ i72ch. from cscapiq. Temperature . . . 138" C. Pressure . . . 50 lb. Feed Water. Total solids . . . . . 58-4 Nitric acid (N,05) . . . . trace Chlorine (Cl) . . . . 2.65 Carbonic acid (CO,). . . . . . 7.31 Oxide of iron etc. . . 0.30 Lime (CaO) . . . 13-47 Magnesia (MgO) . . . 6-29 Sulphuric acid (SO,,i ' ' . 20.06 Silica (SiO,) . . . . . . . 1.10 164' C. 181" C.194" C. 100 lb. 150 lb. 200 lb. 58.6 trace 4.3 23-28 3-04 0.18 1-03 10.47 7 *oo 54.10 trace 4-0 23-48 1.65 0.83 0-18 9.80 5.74 54-52 trace 3.9 23.77 1.41 0-45 0.30 11.30 4-41 TABLE IX. After u11o~uiy for Water Evuporatecl. Total solids . . . _ . . . Nitric acid . . . Chlorine . . . . . Sulphuric acid . . . . Carbonic acid . . . Silica . . . . Oxide of iron . - . Lime . . . . Magnesia . . . . . 58.4 trace 2-65 20.06 7.31 1-10 0.30 13-47 6.29 36-11 trace 2-65 14.34 1.87 0.11 0.63 6-45 4.31 32-97 trace 2.65 15-55 1.09 0-55 0.12 6-48 3.S0 3 7 *05 trace 2.65 16.15 0.96 0.31 0.20 7-68 2.99 52.88 trace 3.55 24.11 1.52 0.46 0.11 2.73 13-7 39 4 7 trace 2.65 18-00 1.13 0.34 0*08 10.23 2.03 2 0 5 O C.250 lb. 4.399 trace 4.3 16-88 1.54 0-42 0.15 10.00 1.81 26.78 trace 2-65 10.40 0.83 0.25 0.09 6.16 1.11 The samples dealt with in Table VIII. were drawn from a new boiler under the The water was kept for t'en minutes at the pressure conditions stated in the table 180 THE ANALYST. stated and at the end of that time a sample was taken. The steam was kept as far as possible from evaporating but it is quite evident that before 50 pounds’ pressure was reached a considerable amount of concentration had taken place. After that there are curious differences in the chlorine figures for which I am quite at a loss to account except on the supposition that some fresh feed water was allowed to get into the boiler.The time during which each of the stated pressures was maintained was unfortunately so short that the full effect could not be produced, and could the period have been twenty times as long it would have been much better. This however would have necessitated extending the whole experiment beyond one day and could not conveniently be arranged for. The mistake however carried with it a certain compensation for it disclosed a phenomenon which under other circumstances would probably not have been revealed. As a rule water drawn from a boiler is of course very turbid but the particles are large and settle down very quickly leaving the supernatant liquid quite clear. I n the case of those samples the water was turbid or it would be better described as opalescent but the particles were so fine that they were invisible when examined under the microscope with a one-sixth objective.I t was absolutely impossible to filter the liquids clear and I had to make the analysis with the turbid fluid. At the end of several months, however the particles seemed to have got larger and heavier and eventually sank to the bottom. When shaken up after this the liquid settled down clear almost immediately. Dealing first with Table VIII. the total solids appear to be almost unaffected by 50 pounds pressure ; but when allowance is made for the small amount of con-centration that has taken place (Table VIII.) it is seen that there has been % considerable reduction amounting in all to 29 parts per 100,000 of feed water which appear to be made up roughly speaking of 5.7 SO:$ 5.4 COr 7 of CaO 2 of MgO and 1 of SiO, while the Fe,O has increased owing no doubt to action on the metal of the boiler.At all the higher pressures the total solids undergo further diminution with the exception of the figure in the fifth column where there is a slight but unmistakable, increase which is more conspicuous when calculated on the feed water as in Table VIII. Between the time when a pressure of 150 pounds was reached and that when 200 pounds was registered something seems to have happened which I cannot at present satisfactorily explain. The result is such as might be produced by a sudden inrush of feed water. I n any case I cannot attribute it to errors in the analytical determinations as most of the results relating to these two samples were done in duplicate.Between 200 and 250 pounds there is a sudden aiid very marked fall in the total solids which may be fairly put down to the action of the increasing pressure and temperature on the solubility of calcium and magnesium sulphates as it is plain from Table VIII. that the great bulk of the loss in total solids in the sixth column is accounted for by reductions in the SO, CaO and MgO. The lime is equivalent to 24.2 parts per 100,000of calcium sulphate. Tilden and Shenstone’s curve for the solubility of calcium sulphate in pure water indicates that from 25 to 26 parts per 100,000 should be soluble at the temperature attained unde THE ANALYST. 181 the 250 pounds pressure which is a sufkiently good agreement.At 200 pounds pressure Tilden and Shenstone’s curve gives the solubility as about 29 parts per 100,000 while the lime in the boiler water at that pressure is equivalent to 33 parts per 100,000 of calcium sulphate. At the lower pressure given in Table VIII. the point of saturation for calcium sulphate is never reached and so the SO remains practically the same or increases slightly ; the lime decreases at first until most of the carbonate has been deposited-Le. till 100 pounds pressure is reached-after which it increases very slowly until at 200 pounds a saturated solution remains. A considerable proportion of it remains in solution throughout the whole series of samples. I n Table VIII. at 50 pounds pressure there is actually more in solution than in the feed water and even when allowance is made for the concentration the loss only amounts to one-third of the whole It seems therefore fairly obvious that the carbonic acid which has gone out of solution is mainly combined with lime unless, indeed magnesium carbonate is deposited only to part with its carbonic acid imme-diately afterwards ; but even then it is not easy to see how the latter could get once more into combination with any of the bases still left in the water.From the time 100 pounds pressure is reached practically no combined carbonic acid leaves the water and yet the MgO goes on disappearing in regularly increasing amounts for every 50 pounds rise of pressure. That the MgO should not be deposited as long as any CaO remains in solution is quite in accordance with the observations of C.H. Bothamley (Chem. SOC. Jozcrn, 1893 698) who found that when solid calcium carbonate is left in contact with a solution of magnesium sulphate or solid magnesium carbonate with a solution of The magnesium behaves in a somewhat unexpected manner. calcium sulphate magnesium sulphate is always eventually found in calcium carbonate is deposited. TABLE X. Lamashire Boiler working presswe 70 to 80 lbs. Feed Water. Nitric acid (N,OJ 1.315 Chlorine (Cl) . . . . 1.70 Carbonic acid (CO,) . . . 8.68 Sulphuric acid (SO:,) 3.57 Oxige of iron etc. Magnesia (MgO) . 0.81 Total solids . . 33.7 Silica (SiO,) . . . Lime (CaO) . . 11.8 . . Water in Boiler after working 82 hours.3.587 15.75 4.49 18.37 5.10 0.4 27.0 0.43 115.0 Water in Boiler after working 468 hours. 6.48 37.0 6.07 29.96 8.35 0.32 13-55 0.18 182.0 solution and The same Water evaporated at about 6 oz. per square inch. 16.29 37.00 1 -99 59.92 2.88 0.76 47.76 3.37 235.0 Table IX. contains the analytical results of two samples taken from a boiler, using New River water at the expiration of the periods stated together with those of the feed water I n order to get some idea of the difference of composition produced by evaporating at the ordinary pressure and at high pressure a quantity of New River water was evaporated in the laboratory until it had the same chZorine figure a 182 THE ANALYST. the sample taken from the boiler after it had worked 468 hours.This was then analysed and the results are placed side by side with those for the boiler sample of the same concentration. The value of the figures is somewhat lessened by the fact that an organic boiler fluid was used in the boiler. Only 2$ gallons however was employed during the whole period and it is probable that only the nitrates were in any way affected by it. Of course in the water evaporated in the laboratory which was distilled from a 5-gallon tin can which was replenished until the residue had the desired concentra-tion no boiler fluid was used. Table X. gives the figures for the same samples after allowance has been made for evaporation in the usual way. TnnLE XI. Inci-nsta-After After Eval’o’ated tion from Boiler.Parts 468 Ordinary Honrs. Hours. Pressure. per cent. Nitric acid (N,O;) . 1.32 0.39 0.30 0.75 moisture and Chlorine (Cl) . 1-70 1-70 1.70 1.70 organic matter} 4’26 Carbonic acid (CO,) 8.68 4.84 2-80 0.09 32.65 Sulphuric acid (SO,) . . . 3.5’7 1.98 1.38 2.7’5 4.42 Silica (SiO,) . . - 0-55 0.38 0.13 7-24 a t 82 Feed Water, Oxide of ir& etc. . - 0.04 0.01 0.03 Lime (CaO) . 11.8 2.91 0.62 2.19 Magnesia (MgO) . . . . 0.81 0.05 0.008 0.15 Total solids . . 33.7 12.41 8-36 10.8 0.39 44.84 6.20 The differences between the analytical results obtained from the samples of the same concentration evaporated at different pressure are much greater than would be expected. The N,O is between two and three times as great in the water evaporated a t ordinary pressures but this is no doubt partly accounted for by the presence of the boiler fluid ; but of course it is quite possible and indeed probable that nitrates are more readily reduced by the metal of the boiler at high than at low temperatures.The tin can in which the laboratory sample distilled had lost most of the tin from its inner surface so it is not surprising to find in Table X. that even here the nitric acid has been considerably reduced in amount. The most surprising difference is found in the carbonic acid. The figures for it in this and in all the tables are really the alkalinity e:qwessecZ as GO,. (In the in-crustations the GO figures are the result of direct estimation.) There is actually less in the water evaporated at the ordinary temperaturs! than in the sample taken froin the boiler.As the estimations were done in duplicate I am not disposed to attribute the discrepancy to error of analysis. A number of possible causes at once suggest themselves but it would be unwise to speculate without further investigation. The difference here may fairly be put down to the high pressure and temperature coni-bined affecting the solubiIity of the calcium sulphate. The behaviour of the lime is almost as puzzling as that of the carbonic acid. 111 spite of the latter having almost entirely disappeared when the water was concen-The SO is exactly double in the fourth column of what it is in the third THE ANSLY ST. 153 trated at ordinary pressure three times as much lime remains in this sample as in that taken froin the boiler.A glance at Table X. however shows that the loss of lime when concentration takes place at ordinary pressure is mainly due to the deposition of calcium carbonate the amount of sulphate of lime leaving the water being very small. At higher pressures it has already been seen that the latter salt hecornes much less soluble. Finally the magnesia has diminished considerably less at the low than at the high pressure which is quite in keeping with what happened in some of the other series of analyses. The temptation to theorize and to draw conclusions even in the complicated phenomena under discussion is very great but the series of analyses are not suffi-ciently extended and do not deal with waters of sufficiently varied types to justify it.They do however suggest many points of theoretical interest which require investi-gation and may perhaps eventually pave the way to a clearer knowledge of the behaviour of salts in solution when heated under pressure. TI have to express my indebtedness to Mr. Charles E. Franck my late assistant, and to Mr. F. W. Arnaud for valuable assistance in carrying out the somewhat monotonous series of analyses. DISCUSSION. Dr. RIDEAL said that an investigation of this kind ought to throw some light on the mineral constituents of natural water. The composition of natural water must depend upon the temperature and pressure at which the saline constituents came into contact with the water. Mr. JENKINS desired especially to thank the author for the figures which the paper contained which would be of great interest to many chemists.He would like to hear whether the author had any experience of an alkaline water such as that referred to in Table V. showing after evaporation any evidence of caustic alkali. Dr. Paul had some considerable time ago recorded results indicative of the presence of caustic soda as well as of carbonate of soda in boiler water. It was within his own knowledge that water softened with a small quantity 'of soda (introduced as caustic soda but fully carbonated before the water was put into the boiler) contained, after concentration in the boiler small quantities of caustic alkali as shown by titration with phenolphthalein and methyl orange. He had himself met with a case of salt scale from a land boiler which had to use water containing a considerable quantity of common salt.This scale contained about 80 per cent. of sodium chloride, most of the remainder being magnesium sulphate. Mr. ALLEN said that a good deal of the effect of magnesium chloride was mitigated in the presence of an excess of sodium chloride whereby it might be converted into a fairly stable double chloride of magnesium and sodium which did not decompose on evaporation. X similar reaction was to be observed in the case of magnesium chloride and ammonium chloride a double chloride of magnesium and ammonium being formed which would stand evaporation. In fact this was the ex-planation of the fact that sea water could be used in a boiler without serious corrosion taking place. Any calcium sulphate present in a boiler water (at any rate from 184 THE ANALYST.high-pressure boiler) must be looked upon as absolutely insoluble it being a well-established fact that calcium sulphate was insoluble in water under a pressure of, say two additional atmospheres. ITaving regard to the conditions under which water could be softened by means of sodium carbonate mixed perhaps with lime he was driven to the conclusion that calcium carbonate was not insoluble in water under all conditions as was supposed to be practically the case and that it might often exist permanently in solution to a considerable extent perhaps in a colloid condition, in which it was not readily precipitated by boiling. I n instances within his recent knowledge at least two or three times as much sodium carbonate had been added to water as was theoretically sufficient to precipitate all the calcium carbonate and yet the water contained calcium carbonate representing a hardness of 7" or 8 O not capable of precipitation by an excess of sodium carbonate.Mr. TV. T. BURGESS inquired what was the source of the alkaline water referred to in Table V. Mr. BEVAN said that he would like to hear how the carbonic acid had been estimated. Mr. CHAPMAN said it was interesting to note how completely the magnesia seemed to have disappeared in two of the cases referred to. He would like to hear whether the author was of opinion that the whole of the magnesia had become converted by double decomposition into magnesium hydroxide. The PREsrDmT (Mr. Fisher) said that he also had noted the alkaline water referred to in Table V.and had a certain amount of curiosity to know from what geological formation it came. It was a common experience to find alkaline water whenever a bed of clay was pierced at some distance from the outcrop of the porous beds. I t seemed as though the magnesia disappeared as the carbonic acid diw appeared from the water. Where the carbonic acid remained as was indicated in Table V. it was bound by the potash and soda and so the magnesia had not any control over it. I t was interesting to notice how well the chlorine served as an index of concentration in connection with questions as to the formation of scale. The concentration which took place in the chlorine where it was originally present in small quantities afforded a valuable index of the ratio of feed water to evaporated water ; but where the chlorine was higher originally than in most of the cases now referred to there might not be quite so much certainty in applying that comparison.Mr. CRIBB in repiy said he saw no reasonfor supposing that caustic soda might not be present in boiler water as the result of some double decomposition though he had not looked for it in the course of the present investigation. With regard to the question of the insolubility of calcium sulphate all his analyses showed that at any pressure at which he had experimented a considerable quantity of calcium sulphate remained in solution. Had calcium sulphate been quite insoluble all the lime should have disappeared seeing that there was always more sulphuric acid present than was required by the lime ; but in no case had this happened.The water referred to in Table V. came from the chalk under the London clay. The figures given under the heading '' Carbonic Acid " were really the alkalinities of the waters expressed as GO,, and were obtained by adding excess of standard acid and titrating back with alkali, using methyl orange as indicator. The end reaction was always considerabl THE ANALYST. 185 obscured in the case of the very concentrated waters. He therefore could not claim any very great accuracy for the carbonic acid determinations in these cases. He was of opinion that the magnesia in the scale referred to in Table 11. was in the form of oxide and not of hydroxide although in all the published analyses of scales he had seen the magnesia was put down as hydrate.It was pretty generally accepted that calcium sulphate was deposited as a hydrated sulphate and afterwards underwent conversion into anhydrous sulphate and in view of the high temperature to which one side of a thick incrustation would be exposed there was no reason why magnesia should not also become dehydrated. Mr. JENKINS said that he had often found considerable quantities of calcium sulphate present in blow-off waters; and his experience was also that in the case of such waters the magnesia had nearly entirely disappeared. If one considered the magnesia as present in the form of carbonate rather than of chloride the method of its precipitation became clear. Mr. ARCHBUTT who was unable to be present at the reading of the paper has forwarded the following remarks : One of the most interesting facts brought out by the paper was the very cornplete manner in which magnesia becomes precipitated in the boiler.This he was able to confirrn from some analyses of his own. I t seems probable that this is brought about by the calcium carbonate reacting with the magnesium salts as shown by the following equation CaCO + NgSO i- H,O = CsSQ + hlg(OH) + CO ; for Bohlig has shown that when calcium carbonate is boiled with a solution of magnesium sulphate, CO is evolved calcium sulphate is found in solution and basic magnesium carbonate is precipitated. If the temperature be high enough the precipitate consists of magnesium hydroxide (Zeits. And. Chem. 1879 195). The boiler scale in Table ITI.consists mainly of CaSO and MgO; and as the original water contained a fair amount of carbonate the whole of the precipitated calcium carbonate appears to have been used up in decomposing magnesium salts. It would be interesting to know what would happen in the case of a water entirely free from carbonates. Another important fact confirmed by Mr. Cribb’s experiments is that calcium sulphate does not as commonly stated become insoluble in water at 302” F., corresponding to a boiler pressure of 55 pounds per square inch. ,4s Tilden and Shenstone’s experiments related only to solutions of calcium sulphate in pure water and in water containing chlorides it is satisfactory to find their results practically confirmed under conditions of actual boiler practice. I t is a pity that in the interesting experiments contained in Table VIII. the heating at each temperature could not have been maintained for a longer period but the results confirmed by other analyses in the paper seem quite to dispose of the contention that by merely heating hard water to 350” F in closed heaters without chemicals the hardness can be reduced uniformly to 5 or 6 degrees as has been stated. This statement can only be true of waters the hardness of which is mainly temporary. Nevertheless it seems that after the removal of the temporary hardness a water containing a moderate amount of calcium sulphate might be prevented from forming scale by the judicious use of the blow-off cock and sufhiently frequent washing out of the boiler so as to prevent the calcium sulphate from reaching the saturation point. Practical experience in many places seems to confirm this supposition 186 THE ANALYST. The author’s experiments and observations on the behaviour of magnesium chloride solutions when evaporated and distilled afford valuable information and his promised further experiments on the behaviour of such solutions when distilled under pressure will be awaited with interest as beyond the fact that waters containing much chloride and magnesia are found to be corrosive to boilers our knowledge is not as definit.e as it might be

ISSN:0003-2654    

DOI:10.1039/AN900250169b

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年代:1900

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186 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. Determination of Chloral Alcoholate in Chloral Hydrate. F. Schmidinger. (Moizntsh. Clze?ii., 1900, xxi., 36.)-Meyer and Haffter ( B e y . , vi., 600) have recoin- mended a method which is quoted in the Commentary to the Austrian Pharma- copoeia, depending on a titration of the chloral hydrate with normal sodium hydroxide. According to the equation CCl,CH(OH), + NaOH = CIIC1, + HCO,Na + H,O 100 parts of the pure hydrate should react with 24.17 parts of soda, whereas 100 parts of chloral alcoholate only require 20.67 parts of alkali. The process is useful to ascertain whether a particular sample is pure; but it can only indicate the presence of alcoholate provided other impurities not capable of reacting with sodium hydroxide are absent.The author finds that Zeisel's methoxyl method (Monatsh. Chenz., 1885, vi., 992) is better adapted for the examination of chloral hydrate, and that it gives satisfactory results. This process is carried out by boiling the substance with 10 C.C. of hydriodic acid of specific gravity 1.68 in a current of carbon dioxide, the flask being attached to an inverted condenser which is supplied with water at 40" or 50" C. The vapours pass through bulbs charged with water and amorphous phosphorus maintained at 50" or 60" C., and are then absorbed in two flasks filled with an alcoholic solution of silver nitrate. After about two hours the whole of the iodine resulting froiii the methylic iodide which is produced by the action of the hydriodic acid upon the methoxgl conipound is converted into silver iodide ; the alcoholic solution is diluted with water, and the precipitate is weighed as usual.About 1 or 2 grammes should be operated upon. F. H. L. Detection of Antifebrin [Acetanilide], Phenacotin, Exalgin, and P-amido- phenol in Antipyrine or Quinine. (Oesterr. Chem. Zeit., 1900, iii., l%.)-Two processes are recommended : Distillation with phosphoric acid for the detection of the acid radicle and observation of certain changes in colour, and distillation with potassium hydroxide for the detection of the basic constituent. One gramme of the substance is cautiously warmed with 3 C.C. of P. N. Raikow and P. Schtarbanow.THE ANALYST. 187 phosphoric acid, specific gravity 1.7, to a temperature short of that which decomposes the aniline phosphate, when antifebrin, phenacetin, and exalgin yield distillates of acetic acid.Antipyrine, antifebrin, and exalgin become more or less yellow or brownish yellow ; phenacetin gives very characteristic colours : at first the mixture is pink, then wine-red, red-violet, violet, bluish green, and finally dirty green. If the liquid is cooled at the red-violet stage, it retains its colour unaltered for a long time, and this colour is not affected by the presence of antipyrine or antifebrin. The violet tint appears immediately antifebrin containing only 2 per cent. of phenacetin is boiled with phosphoric acid. To detect the base, a few decigrammes of the sample are heated with 2 to 4 C.C. of strong aqueous potash, allowing the distillate to drop on to a little chloride of lime solution in a test-tube, which is changed (if necessary) after each single drop has fallen.-4ntifebrin gives the violet colour characteristic of aniline with its first or second drop, and the tint steadily becomes stronger. With phenacetin, the first drops remain colourless, subsequent ones yielding a brick red, due to the phenetidine, while on further heating the chloride of lime becomes turbid, and an amorphous red substance collects on the surface of the liquid, which finally turns yellow and clear again. Mixtures of phenacetin with 2 per cent. of antifebrin may be recognised by the different boiling-points of their basic constituent, changing the receivers so as to collect the pure aniline in one, and the phenetidine in the second, third, or fourth.When pure antipyrine is boiled with caustic potash, the chloride of lime remains colourless ; but afterwards a substance distills which renders the solution milky, eventually forms white scales, and, combining with aniline and phenetidine, may prevent them yielding their characteristic colour reactions. This substance, how- ever, which is neither antipyrine itself nor a chlorine derivative, is not produced till after the aniline from a mixture of antipyrine and antifebrin has passed over, SO that 2 per cent. of the latter is easily to be found. Mixtures of antipyrine with phenacetin do not exhibit the proper red colour unless the proportion of the phenacetin is relatively high ; the chloride of lime becomes yellowish green, then yellowish gray.A material composed of 0.1 gramme of antipyrine, 0.01 gramme of antifebrin, and 0.03 gramme of phenacetin, yielded the violet aniline colour with its first drop of distillate, which was changed to an orange by the next drops, so that both the latter bodies could be identified in the antipyrine. Distilled with potash, exalgin yields oily drops of methylaniline floating on the chloride of lime solution ; these quickly turn green, and a dirty-brown precipitate appears. The test succeeds in the presence of antipyrine and antifebrin. Quinine gives rise to no volatile compound on distillation with potassium hydroxide which is capable of affecting the solution of bleaching powder. Before testing with phosphoric acid the free base must be liberated from its salts ; then the alkaloid yields no acid vapours, while the liquid in the retort first becomes yellow, then shows an intense ‘‘ yellow-bluish-green ” fluorescence. Traces (O*OOOl gramme) of p-amidophenol in these febrifuges are indicated by a deep violet colour when the sample is shaken with the phosphoric acid in the cold ; the solutions ought to be colourless. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9002500186

出版商:RSC    

年代:1900

数据来源: RSC

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188 THE ANALYST. ORGANIC ANALYSIS. Sugar Estimation in Zeiss’s Immersion Refractometer. J. A. Grober (CeiztraZbZ. inn. Meed., 1900, xxi., 201 ; through Chew. Zeit. Rep., 1900, 73.)-In the original article this apparatus is fully described, and its sphere of usefulness outlined, By observing saccharine urine before and after fermentation, the difference in reading divided by 2.9 gives directly the percentage of sugar ; and by examining albuminous urine before and after precipitation with acetic acid, the difference divided by 0.3 gives the albumin in parts per 1,000. F. H. L. The Solubility of Essential Oils in Sodium Salicylate. M. Dugk. (BUZZ. c7e Z’Acad. belge royalo ; through Jozwn. Plzamz. Chim., 1899, x., 500-504 ; cf. ANALYST, ;this vol., 72.) Oil of Peppermint.--This yields to dilute salicylate solution (4 : 1.5) 78 per cent.of soluble products containing menthone and nearly the whole of the menthol. The insoluble portion consists principally of hydrocarbons (’? menthene), sad other com- pounds but little known. The menthol contained in the soluble and insoluble portions may be estimated in the following manner : Several grammes of the substance are boiled for two hours under a reflux condenser with 10 C.C. of acetic anhydride and 2 grammes of sodium acetate, and the acetyl value calculated from the difference between the amount of sodium hydroxide required by the acetic anhydride used and that required after acetylation. The amount of menthol is obtained by the formula 60 x A 156- ’ X=- in which A represents the amount of acetyl which has entered into combination, and 60 and 156 the respective molecular equivalents of acetic acid and menthol.OiZ of Black MustcLrd.-This consists of ally1 sulphocyanide, and is insoluble in the salicylate solution. Oil of Bitter Oranp-The aldehydic compounds (citral, etc.), which are present in very small quantities, dissolve in the salicylate solution. The limonene remains undissolved. OiZ of Ro~enzary.-~4n oil of doubtful purity yielded to the salicylate solution 16 per cent. of substances, with a strong odour of camphor. The insoluble portion had a higher rotatory power than the original oil. Rose Oil.--This is completely soluble in dilute salicylate solution (4 : 1). When adulterated with paraffin compounds it is only partially soluble. SnntaZ Oil (Indian) contains only traces of compounds soluble in salicylate solutions.Oil of Turpentine.-When pure, this is insoluble in the salicylate solution ; but when oxidized, the aldehydic compounds which have been produced are soluble, The test is valuable in detecting the presence of turpentine in soluble essences. OiZ of Thyme.-The whole of the thymol and carvacrol are extracted by the The hydro- salicylate solution, and when separated form a colourless syrupy liquid. carbons are left undissolved. C. A. M.THE ANALYST. 189 Terpeneloss Gregor. (Cl'zem. these oils which known firms, and Essential Oils of Lemon and Orange. N. Wender and G. Z e d . , 1900, xxiv., 210.)-The authors have examined samples of were described as being (' terpeneless," obtained from three well- they record their results herewith.The opticity was determined in a, 100-millinletre tube at 20' C., using sodium light passed through a chromate solution; and owing to the high rotatory power of the oils themselves, they were tested in the form of alcoholic solutions, preliminary experiments having shown that no appreciable errors in the readings are introduced by the dilution. As the terpenes of the essential oils are less soluble in water than the oxidized constituents, experi- ments were also tried to discover a relationship between the water-solubility of the " terpeneless" oils and their rotatory power, these being carried out by shaking a 10 per cent. alcoholic solution in a tall, graduated cylinder at 15' C. with increasing quantities of water, till a homogeneous, faintly opalescent liquid was produced.The last column in the table indicates the volume of water in C.C. required to dis- solve 1 c . ~ . of the 10 per cent. alcoholic solution. Hark. Strength of Per Cent. Solution, OPtiCitY of OTticitY Of SolubilitJ-, Solution. 1 ure Oil. Lemon Oil ... H. H. 25-61 - 1.90" - 7.41" 400 $ 9 t ) ..- Sch. and Go. 25.09 - 0.25" - 0.99" 500 Orange Oil ... H. H. 25.87 + 3-40' + 13-10" 500 9 , *, ... 0. W. and Go. 23.83 + 1-75" f 7-34" 1,000 ,, ,, ... Sch. and Co. 25.97 + 16.60" + 63.91" 1,000 ,, ,, . . 0. W. and Co. 20.85 + 14.50" + 69.70" 1,200 Especially in the case of terpeneless orange oil, the solubility in water falls as the rotatory power rises ; but it is clear that these oils are still o€ very uncertain com- position, even when procured directly from reputable firms.F. H. L. Estimation of Chromium in Chrome-tanned Leather. P. von Schroedcr. (Dez~tsche Gerber Zeit., 1899, December ; through Zeits. angezo. Chenz., 1900, 142.)- About 3 grammes of the leather are thoroughly ignited for two or three hours in a porceliin crucible. The residue is moistened with 60 per cent. nitric acid (specific gravity, 1-37), and solid potassium chlorate is added. The crucible is heated on the water-bath with fresh additions of acid and chlorate until the solution becomes red, when it is evaporated to dryness two or three times with strong hydrochloric acid. The solid matter is then washed into a porcelain basin by means of water, a few drops of dilute sulphuric acid are introduced, and sodium peroxide is cautiously dropped in until the green liquid changes to pure yellow. The hydrogen peroxide (which would reduce the chromic acid when the solution was acid, but which is inert in presence of alkali) is next removed, either by simple evaporation or by means of a, little alcohol; the whole is mixed with 25 C.C. of 10 per cent. solution of potas- sium iodide and 25 C.C. of 1 : 5 sulphuric acid, and the iodine liberated is titrated with decinormal thiosulphate. Seven samples of chrome-tanned leather gave 0.82, 1-68, 1.43, 3.4, 2.9, 3.22, and 2.25 per cent. of metallic chromium respectively; but it should be noted that there appears to be no connection between the proportion of chromium and the quality of the leather. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9002500188

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年代:1900

数据来源: RSC

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190 THE ANALYST I N O R G A N I C A N A L Y S I S . The Gas-Volumetric Estimation of Hydrogen. A. Colson. (Ac, c k s Sciences, 1900, cxxx., 330 ; through Joztm. Pliamz. Chinz., 1900, xi., 335.)-This method is based upon the fact that hydrogen is absorbed by silver hydroxide. The reaction takes place slowly in the cold, but at 100” C. is rapid, and furnishes a means of separating hydrogen from a saturated hydrocarbon or from oxygen. The mixed gases are introduced into a eudiometer, provided near the top with a horizontal side-tubulure, in which has previously been placed 1 to 2 grammes of silver hydroxide. On heating the side-tubulure the mercury rises in the eudiometer, and the absorption is complete in two and a half to three hours. In calculating the true volume of the residual gas, allowance must be made for the tension of the water-vapour formed during the reaction.Hydrogen is conipletely absorbed, even at a very low pressure, whilst, as the author shows in his test estimations, no absorption of ethane, methane or oxygen takes place. C. A. M. The Estimation and Scparatim of Copper by means of €lydrnzine Sulphate or Hydrazine Hyd-roehloride. P. Jannaaeh and K. Bicdermann. (BcP-ichte, 1900, xxxiii., 631-636.) Estimatioiz of Copp-.-The hot solution of the copper salt is poured, with constant stirring, into a porcelain basin containing a solution of 5 gramines of pure sodium hydroxide in 50 C.C. of water. The resulting precipitate is reduced to cuprous hydroxide by adding 1 to 2 C.C. of a boiling 3 per cent. solution of hydrazine sulphate, and slowly heating the basin on the water-bath while its contents are continually stirred.On the further addition of 3 C.C. of the hydrazine sulphate solution the copper is reduced to the nietallic state. After cooling, or diluting the liquid with boiled water, the precipitate is collected on n filter, washed with hot water, dried at 90” C., the paper ignited apart from the copper, and the latter oxidized over a Bunsen flame in a current of oxygen and weighed. The results thus obtained in test experiments with copper sulphate were satis- factory. Separatioiz of Coyper f r o ~ z Z!iizc.-In the authors’ experiments the solution of the mixed sulphates was introduced drop by drop into a basin containing 50 C.C. of 10 per cent. sodium hydroxide solution.Five C.C. of a 3 per cent. solution of hydrazine sulphate were then added to the cold liquid containing a large excess of sodium hydroxide, and the whole slowly heated on an asbestos board. After about five minutes there was a complete precipitation of the copper, which was collected and oxidized as described above. The filtrate containing the zinc was treated with hydrochloric acid, until the precipitate, which formed after some time, again dissolved, and the liquid was distinctly acid. The zinc was then precipitatsd as carbonate, which was ignited and weighed in the usual manner. Sometimes the zinc oxide obtained was not com- pletely soluble in dilute acetic acid owing to the presence of traces of silica.THE ANALYST. 191 In this way the following results were obtained IN SOLUTIONS U S I ~ PER CEXT.FOCNI) PER CENT. -*--\ r 'r \ Copper. Zinc. Copper. Zinc. 16.77 7-74 16-73 7.68 15-69 8.68 15.61 8.68 Seyaratioiz of Copper from Arse?zic.-A solution of copper sulphate and arsenic acid was introduced drop by drop into 40 to 50 C.C. of 10 per cent. sodium hydroxide solution, the liquid warmed after the introduction of 4 to 5 C.C. of hydrazine sulphate solution, and the precipitated copper estimated as before. The solution containing the arsenic was acidified with hydrochloric acid, a little nitric acid being added with it towards the end of the neutralization, and the whole evaporated to about 80 c.c., care being taken to have some nitric acid continually present. The clear liquid when cold was treated with ammonium hydroxide in excess, and the arsenic precipitated with freshly-prepared magnesia mixture, and estimated in the usual may.Results : TAKEN PER CENT. POUND PER CENT. --- -A- Copper. Arsenic. Copper. Arsenic. 17.53 23.41 17.46 23.37 13-68 35.99 13-56 35.24 Separation of Ccpper jrom Ti?z.-&lixtures of pure copper and tin were dissolved in aqua regia, the solutions diluted with an equal volume of water, and added drop by drop to a hot solution of sodium hydroxide containing fifteen times more alkali than the weight of the dissolved metals. After the addition of 2 to 3 grammes of hydrazine hydrochloride the liquid was heated, and the heating continued for some time, in order to dissolve as sodium stannate any tin carried down with the copper. I n the absence of sulphates any tin readilydissolved.The copper was collected on a double filter, washed with boiling water, and if necessary with dilute sodium hydroxide solution and again with water, dried, oxidized and weighed. The filtrate was rendered slightly acid with strong hydrochloric acid, and the tin precipitated with ammonium hydroxide. The precipitate was dissolved by adding ammonium sulphide, and the liquid heated for a time on the water-bath and then slightly acidified with hydrochloric acid. After being heated for about an hour on the water-bath, the resulting precipitate of tin sulphide subsided and could be easily filtered. I t was washed with warm hydrogen sulphide solution, ignited in a current of oxygen and weighed. The following results were obtained : TAKEN PER CENT.FOUND PER CENT. 7- .-- - Copper. Tin. Copper. Tin. 25.81 74-18 25.72 74.06 31.28 68-61 31.28 68-48 C. A. M. - . __ ~~ - The Analysis of Xolybdenum Alloys. H. Borntrager. (zed. and. Chem., 1900, xxxix., 91.)--As a supplement to his method of analysing molybdenum glance192 THE ANALYST. (ANALYST, xxiii., 332), the author describes the following process for determining molybdenuin in its alloys : About 1 gramme of the sample is dissolved in 50 C.C. of aqua regia on the water- bath, the solution evaporated in a porcelain basin, and the nitric acid expelled by means of hydrochloric acid. The residue is taken up with 50 per cent. alcohol, and the liquid filtered. The residue left on the filter will now contain the bulk of the molybdic acid. The filtrate is evaporated to dryness, and the residue once more taken up with alcohol, after which treatment the remainder of the molybdic acid will be left as a residue.The rnolybdic acid in the two residues can then be weighed directly, whilst the metal in the solution can be estimated in the usual way as oxide. From an alloy known to contain 66 per cent. of molybdenum and 44 per cent. of iron, the author obtained by this method 65.6 per cent. of molybdenum. C. A. &I.. The Detection of Boric Acid in the Form of Borates. H. Borntra,ger. (Zeit. anal. Chem., 1900, xxxix., 92.)-When borates are heated with hydrochloric, nitric, or snlphuric acid, a Bunsen flame is not coloured green. On the other hand, when heated with hydrofluoric acid alone, or with ammonium nitrate and ammonium chloride, or with sulphuric acid and hydrochloric acid, or sulphuric acid and nitric acid, or hydrochloric acid and nitric acid, borates impart a bright green colour to the flame ; and this coloration is more intense, and appears sooner, than that obtained on heating the salts with alcohol and sulphuric acid.C . A. M. A New Method of estimating Bromides in the Presence of Chlorides and Iodides. (Zeit. anal. Chem., 1900, xxxix. , 81-91.)-Bromine can be determined in the presence of chlorine by taking advantage of the fact that in an alkaline solution it is oxidized by chlorine to bromic acid, as in the equations : Br + 6KOH + 5Cl= KBrO, + 5KCl+ 3H20, and KBr + 6KOH + 3C1, = KBr03 + 6KCl-t 3H,O. The excess of chlorine is converted into chloride and chlorate ; but as the solution of the latter salt is too weak to act upon iodides in the cold, the amount of bromate formed may be determined by adding a solution of potassium iodide, acidifying, and titrating the liberated iodine.For the separation of bromine and chlorine from iodine, the author makes use of Winkler’s method, which is based upon the fact that chlorine oxidizes iodine or iodides in acid solution to iodic acid, whilst the bromine is only liberated. Thus, on acidifying a solution of the mixed halides, adding an excess of chlorine water, and boiling the liquid, the resulting iodic acid remains behind, while the bromine and excess of chlorine distil over. On adding potassium iodide to the cooled liquid in the flask, and titrating with & thiosulphate, a sixth part of the iodine found corresponds to the iodine originally present.I n applying these reactions, if the solution contains no iodine, about 1 gramme J. v. Weszelszky.THE ANALYST. 193 of potassium carbonate is introduced, together with a sufficient quantity of chlorine water, and the liquid cautiously evaporated to dryness over a naked flame. The residue, when cold, is dissolved in 100 to 150 C.C. of water, potassium iodide added, and the liquid acidified and titrated with ;& thiosulphate. The number of C.C. used, multiplied by 0.001333, gives the quantity of bromine. When iodine is present, the liquid is placed in a distilling flask, similar to that used by Bunsen and Fresenius in the analysis of manganese peroxide (Fresenius, “ Quantit. Analyse,” 6th edit., i.382). This is connected with an absorption vessel, containing 0.5 to 1.0 gramme of potassium hydroxide dissolved in water, After the addition of a sufficient quantity of chlorine water, the flask is warmed, and when the greater part of the chlorine and bromine has passed over, a current of carbon dioxide is passed through the apparatus until the end of the distillation. The bromine in the distillate and the iodine in the flask are determined by titration with thiosulphate, as described above. When the solution of the halogen contains iron, the latter should be separated by precipitation with potassium carbonate ; arsenic and antimony when present must also be removed. The author gives tables of the results of test analyses of experimental mixtures of bromides, iodides, and chlorides, from which it appears that the method is extremely accurate, even when only minute quantities of the halogens are present. C.A. M. ~ The Determination of Clay in Soils. F. Poquillon. (Bull. SOC. C ~ L ~ Z . , 1900, xxiii., 115, ll6.)-The author recommends the following method as being much more rapid than the usual process, requiring at the outside only two or three days. Ten grammes of the soil are triturated with about 25 C.C. of water added drop by drop, and 100 to 120 C.C. of a solution of ammonium chloride (1 gramme per litre) added to the mixture. The mass is stirred with a glass rod, and after standing for five minutes the supernatant liquid is transferred to a litre flask. The residue is again treated with 100 to 125 C.C.of the ammonium chloride solution, and the liquid again decanted after five minutes, this process being repeated until the washings are clear. About six or eight washings are required in the case of heavy clay soils. The residue is then treated with dilute hydrochloric acid, washed with water, dried, and weighed, the weight giving the amount of total sand. The liquid in the flask is treated with a few drops of hydrochloric acid to dissolve carbonates and to coagulate the clay, after which it is left until the supernatant liquid is clear. The deposited clay is then collected on a weighed filter, washed with water, dried, and weighed. The following results were obtained by this method, and by the ordinary method, which takes from eight to ten days : This usually takes two or three hours. Clay in tke Soil.-Parts per Tlzousaiad. Old method ... 206.0 60.2 198.0 218.0 122.0 129.3 New method .._ 205.9 60.5 198.0 217.1 121.9 129.5 C . A. M.194 THE ANALYST. A New Indicator: Alizarin Green B. J. Formarmok. (Zeit. anal. Chm., 1900, xxxix., 99-103.)-Alizarin Green B, which is manufactured by Dahl and GO., Barmen, is obtained by the action of P-naphtho-quinone-sulphonic acid on (2)-amido- (l)-naphthol-(4)-sulphonic acid. It is a greenish-black powder, which dissolves fairly readily in water, forming a dirty-green solution. It is somewhat less soluble in alcohol, the colour of the solution being flesh-red. On adding a dilute acid to the aIcoholic solution the colour becomes carmine red, whilst alkalies change it to a pure green. Like litmus, it is sensitive to carbonic acid. The changes in the colour reactions are exceedingly sharp, and are as perceptible with an artificial light as in daylight. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9002500190

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

194 THE ANALYST. APPARATUS. Some Improved Still - heads. S. Young. (Jozwn. Chem. SOC., 1899, Ixxv., 679.)-In this article the author draws attention to the various defects of the popular dephlegmators, and shows that the Glinsky tube (glass balls) is inferior even to the Le Be1 Henninger (platinum gauze and lateral reflux tubes). He then describes two new forms of apparatus, which are illustrated herewith. Figs. 1 and 4 represent the “ pear” head of different sizes. I n this the liquid condensed in any particular bulb drops vertically through the lower ones without travelling over the surface; and thus the quantity of condensed fluid is diminished. Figs. 2 and 3 show the ‘( rod and disc ” heads. The discs are flanges of glass constructed on a glass rod by ‘( upsetting” it at the necessary places.In Fig. 2 the main tube is parallel, and the rods-and-discs can be withdrawn ; in Fig, 3 the tube is provided with constrictions, which increase the efficiency of the device. To obtain fractionation equivalent to that yielded by a three-bulb Le Be1 Henninger tube, the rod-and-disc apparatus, or prefer- ably the “ pear” tube is advocated. They are simpler, better suited for the treatment of small volumes of liquid, and at the end of the process return almost all the residue to the still [while, as the makers point out, the “pear” head enables the retort to be recharged without disarranging the whole apparatus, and without danger of breaking the tube]. For an eaciency equal to that of a Young and Thomas dephlegmator of 12 or 18 columns, however, the new heads are too long ; and therefore either the former device, modified according to the illustration on p.700 (Zoc. cit.), should be retained, or preferably an &‘evaporator ” still-head (p. 696) should be adopted. The improved heads are made by J. J. Griffin and Sons. F. H. L.“HE ANALYST. 195 A Laboratory Filter Press. W. t. Loeber. (Chom. hit., 1900, xxiv., 193). -This apparatus is specially suitable for the filtration of hot or volatile liquids where the ordinary suction-pump exhibits certain disadvantages. a is a cylindrical porcelain vessel carrying a perforated false bottom just above its conical base. At the top it is fitted with a flange, the internal edge of which is elliptical in shape; and the cover, also elliptical, is of larger area than the aperture.The cover has an open handle ( b ) , through which a wooden wedge (c) is driven, and this arrangement pulls it upwards against the inner surface of the flange, making a tight joint through the agency of a rubber washer. [This part of the device is precisely analogous to the I ( manhole ” of a steam boiler.] The tube e is closed at it,s internal end, but has a lateral opening; a piece of rubber tube is slipped over it to form a non-return valve. Pressure is applied by means of a pneumatic tgre inflator. In using the apparatus a moistened filter-paper is laid on the perforated bottom; and if the liquid is such that the paper does not lie flat, the two halves of a split porcelain ring are placed on if to hold it down. The cover is then brought within the flange at right angles to its proper position, held lightly with the wedge, and the liquid is run in through a funnel; the cover is next rotated to its correct position, tightened up, and the pressure applied.If the precipitate is one of those that fissure before they are fairly dry, thus permitting escape of air, when the bulk of the filtrate has run through, the apparatus is opened, another paper is laid on the top of the precipitate, the cover is wrapped in a thin sheet of rubber, e.g., a piece of a toy air-balloon, and the joint is made as before. On pumping up, the rubber expands till it fills the space of the filter, pressing the top paper downwards on to the precipitate, and thus acting as a press. To release the pressure it is then necessary to puncture the rubber from beneath by means of a needle ; but the hole in the sheet can be afterwards mended with tyre solution.A cyclist’s pressure-gauge can be added if desired. The machine, made in two sizes, 250 C.C. and 2 litres, is on sale by the Actienges. fur pharmaceut. Bedarfsmittel, Cassel, and has been protected as a ‘‘ Gebrauchsmuster ” in Germany. F. H. L. A Laboratory Apparatus for igniting Large Quantities of Substancee. G. P. (Berichte, 1900, xxxiii., 486.)-By means of the simple device shown Drossbach. in the figure several kilogrammes of solid matter in the form of powder may be ignited in any gas required.196 THE ANALYST. It consists of a tube (R), provided with a funnel (T), and a spiral conveyor (S), driven by a motor. The solid substance is introduced through T into the heated tube, and the gas at E, while the ignited product is discharged at A. If the tube is 30 centimetres long and has a transverse section of 1 square c.c., and the spiral revolves once in a second, the substance will remain €or a minute in the hot tube. C. A. M. - - _______ ~~ __

ISSN:0003-2654    

DOI:10.1039/AN9002500194

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

196 THE ANALYST. DIVISION OF SAMPLES UNDER THE SALE OF FOOD AND DRUGS ACT. QUEEN'S BENCH DIVISION. (Before Mr. JUSTICE DARLING and Mr. JUSTICE BUCKNILL.) MASON 2'. COWDARY. (From the PHARMACEUTICAL JOURNAL, June 9, 1900.) TIIIS was a special case stated by the Justices of Bedford. It stated that, at a Petty Sessions held a t Luton, January 8, 1900, an information was preferred by Geo. Mason, under Section 6 of the Sale of Foods and Drugs Act, 1875, against Ellen Cowdary, that she on November 16 did unlawfully sell to the prejudice of the appellant camphorated oil which was not of the nature, substance and qiaality demanded. The respondent kept a small shop in the village of Leagrave, Beds, and the appellant purchased from her six twopenny bottles of cam- phorated oil. The oil was exposed for sale in bottles which were not apparently prepared by respondent, but each of them bore a label with the name of a chemist in the neighbouring town of Luton.There was no evidence whether or not the bottles were identical in character or appearance, or whether or not the labels all bore the name of the same chemist, but the six bottles were all purchased a t the same time. At the time of the purchase, the appellant inti- mated to the respondent his intention to have the oil analysed, and he divided the six bottles into three lots of two bottles, each of which he sealed up, handing one lot to the respondent, keeping one lot, and sending the other lot to be analysed. Appellant did not open any one of the bottles of oil, or mix or divide the contents ; but the two handed to the respondent were in the same condition as when purchased. The appellant received from the Public Analyst a certificate of the analysis of the contents of the two bottles submitted to him, and the analysis was put in evidence.It showed that the camphorated oil in the bottles analysed contained only 17.5 per cent. of camphor, whereas proper camphorated oil should contain 20 per cent. of camphor. For the part of the appellant, i t was contended that the requirements of Section 14 of the Sale of Food and Drugs Act had been complied with by him, inasmuch as he had divided the article into three parts, each of which was marked and sealed ; but the justices were of opinion that the appellant had not complied with the requirements of Section 14, and, further, that they were not satisfied that the two bottles analysed by the analyst were identfcal in nature and substance with the other two sets of bottles in the hands of the seller and the appellant respectively. They accordingly dismissed the summons. Mr. BOSSEY said the appeal had been made because the appellant wished the point decided whether or not i t was necessary to divide up each bottle in order to comply with Section 14. Without calling on the other side, their lordships held this was a purchase of six separate articles, and therefore each required dividing and analysing. The appeal was therefore dis- missed with costs. _ _ _ - - ~ .~~ AypoINTmwr.-Mr. Norman Leonard, B.Sc., F.I.C., has been appointed Public Analyst f o r the Borough of Northampton, vice Mr. Raymond Ross, resigned.

ISSN:0003-2654    

DOI:10.1039/AN9002500196

出版商:RSC    

年代:1900

数据来源: RSC