摘要:

THE ANALYST. AUGUST, 1896. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. SUMMER MEETING. THIS took place on the afternoon of July 14, when about thirty members and their friends lunched together, and proceeded by steam-launch to the sewage outfall works at Barking, where a tour of inspection was made, under the guidance of Mr. W. J. Dibdin. The party afterwards returned to Greenwich, and dined at the Ship. THE ANALYSIS OF MORTAR. BY W. J. DIBDIN, F.I.C., AND R. GRIMWOOD, F.I.C. (Read at the Meeting, J m e 3, 1896.) The Legal Specijficcbtion of Mortal.. IN the by-laws made by the London County Council, under Sect. 16 of the Metrop. Management and Building Acts Amendment Act, 1878, it is provided that the mortar used under that Act must be composed of freshly-burnt lime and clean sharp sand or grit, without earthy matter, in the proportions of one of lime to three of sand or grit.I n the case of cement-mortar, the cement to be used must be Portland cement, or other cement of equal quality t o be approved by the district surveyor, mixed with clean sharp sand or grit, in the proportions of one of cement to four of sand or grit ; also that burnt ballast or broken brick may be substituted for sand or grit, provided such material be properly mixed with lime in a mortar-mill, I n the by-laws made by the Council under Sect. 31 of the London County Council (General Powers) Act, 1890, it is provided that plastering or coarse stuff shall be coinposed of lime and sand, in the proportion of one of lime to three of sand, mixed with water and hair ; but Portland, Keene's, Psrian, Selenitic, or other cement or plaster of Paris, may also be used for plastering.The lime must be freshly-burnt lime ; the sand must be clean sharp sand, free from loam or earthy matter; the hair must be good and sound, free Erom grease or dirt, and that one pound of hair to be used to every three cubic feet, of coarse stuff. Fibrous material may be used instead of hair, and ground brick or furnace slag, each to the satisfaction of the district surveyor, may be used instead of sand; and the setting coat must be coinposed of lime or cement mixed with clean washed sand, or cement only. Usual Character of Mortcws. Earthy illat t el.. From these extracts froin the by-laws relating to the use of building materials in the Metropolis, it will be seen that an analysis of lime-mortar or cement-mortar,198 THE ANALYST. etc., can be conducted with a degree of accuracy sufficient to indicate very slight departures from the prescribed quantities of the materials used.Unfortunately analyses which have been made from time to time by us have shown distinctly that it is only under exceptional circumstances that mortars which come within these regulations are employed. To take one factor only, the earthy matter: analysis of samples of mortar, made with materials selected as coming within the definition of the by-laws, and in the proportions therein set out, shows that the earthy matter, as determined by us in the manner described hereafter, varied as follows: 1.5, 2-1, 0.14, 0.74, 0.81, 0.61, 0.64, 0.96, 0.85, and 0.70 per cent.; thus showing that the finely-divided matters which may be accidentally introduced by means of the broken brick or sand form but a very small proportion of the actual weight of the mortar.As compared with these, the following results obtained from the examination of a number of samples of mortars taken from a building in course of erection will indicate the great difference in this respect, viz. : 4.9, 3.8, 9.1, 3-4, 14.7, 13.7, 7.4, 10.4, 8.1, 12.3, per cent. so l?Lb le Silicu. Another factor of importance in estimating the quantity of cement in a genuine cement-mortar is that of the soluble silica. As is well known, the silica, soluble in hydro- chloric acid, present in Portland cement will vary between 17 and 20 per cent, ; but if the average is taken at about 18 per cent., it will form a fair bafiis for calculation.If the cement-mortar is made with good Portland cement and clean, well-burnt brick or sand in the proportion of one of cement to four of the grit, there will be about 3& per cent. of soluble silica. In some samples of genuine cement-mortar, the soluble silica was found to be 3.25, 2.5, 3.25, and 2.25 per cent.; as against these samples of gaizzLiize mortar made with lime gave soluble silica equal to 0.9, 1-0, 0.6 traces, and 1.1. If we now turn to the analyses of conznzemiul mortars (see Table V.) above referred to, we find that the soluble silica varied as follows : 0.9, 0.7, 0.7 ; thus showing a very marked difference between this factor under different circumstances.Cnrboi~ic L4cid. A third factor is the quantity of carbonic acid. Genuine mortars made with good materials were found to contain, after the mortar had been made for some three months, carbonic acid equal to 1.02, 1.36, and 1.06 per cent. of carbonate of lime; and the cement-mortars to contain carbonic acid equal to 2-86, 2.86, 1-04, 1.87, 1.45 per cent. of carbonate of lime. Freshly prepared mortar made with good materials contained in two instances 0.3 and 0-4 per cent. carbonate of lime. Against these, the corn- inercial mortars contained 6.42, 6.24, 7.39, 4.52, 8.9, 8.4, 8.0, and 4.5 per cent. ; thus showing conclusively that this factor alone gave such marked indications of the character of the material that it would be almost impossible that a mistake should be made in estimating the character of a given sample of mortar or cement.I t is to be noted that certain bricks contain carbonate of lime, and this should be determined before concluding that the mortar is made with old materials or insufficiently burnt limestone. In Table I. an instance is given of a brick containing 7-77 per cent. of carbonate of lime. The full details of these analyses are given in the tables at the end of the paper.THE ANALYST. 199 Helatioiz of Weight to Volwne (Lime-Moi-tar). In the by-laws it is provided that the quantities ate to be by volume, and not by weight ; therefore the analysis, being stated by weight, must- be converted into terms of volume, In order to show how this is arrived at, the following comparative analysis of a sample of mortar, specially prepared for this purpose, will make the point clear.The analyses of the lime and broken brick are given in Table I. ; and, in Table II., that of the mortar made with one volume of lime and three volumes of brick. I n this case the brick had some old mortar adhering to it, as would happen where old bricks are used. TABLE I. Sample of the Lime used in making Mortar. Lime (CaO) ... ... ... ... ... ... 78.40 per cent. ,, carbonate.. . ... ... ... ... ... 3-22 ,, ,, sulphate ... ... ... ... ... ... 0.64 ,, Soluble silica, iron oxide and alumina ... ... 12-85 ,, Sand ... ... ... ... ... ... ... 4-80 ,, Total ... ... ... 99-91 .. Sample of the Brick used in making Mortar. Per cent. Moisture (loss at 212' Fah.) ... ... 1-27 Lime (CaO) ...... ... ... 1-99 ,, carbonate ... ... ... ... 7.77 ,, sulphate ... ... ... ... 1-03 Soluble silica. iron oxide and alumina ... 3.60 Insoluble matter (crushed brick). .. ... 78.77 This had the appearance of Insoluble matter (fine) ... ... ... 1m69{ having been burnt. - Total ... ... ... 96-12 TABLE 11. Sanqde of Mortar made with One Part by Measzwe of Lime and Three Parts Crushed Brick. Per cent. Moisture, water of hydration, etc. ... 29.71 Lime (CaO) ... ... ... ... 12-85 = 16.06 commercial lime. .. carbonate ... ... ... ... 4.47 ,, sulphate ... ... ... ... 0.61 Crushed brick ... ... ... ... 46.03 Iron oxide and alumina ... ... ... 2.80 Soluble silica, ... ... ... ... 1.85 Loss on ignition ... ... ... ... 0.98 Total ... ... 1 m o { This had the appearance of ...... Earthy matter ... . ' ' 0'70\having been burnt. Commercial lime (containing 80 per cent. of CaO) to crushed brick, 1 to 2.29 by volume. by volume. $ 9 9 , I , ,, I , to all other matters, 1 to 2.86200 THE ANALYST. In this it will be seen that the earthy matter was 0.70 per cent, in the mortar, and the lime (as pure lime) 12.85 per cent., equal to 16.06 per cent. commercial lime of 80 per cent. pure CaO. The brick (Table I.), as already mentioned, contained 7.77 per cent. of carbonate of lime, Another instance is given in Table 111. of the analyses of lime and mortar made therewith and good brick. In this the carbonate of lime was only 1.97 per cent. on the mortar. Moisture, water of hydration, and loss Lime (CaO) ... ... ... ... Garb. lime ... ...... ... Sulphate of lime ... ... ... Iron oxide and alumina ... ... Soluble silica ... Sand and grit ... ... ... ... Earthy matter ... ... ... Loss on ignition ... ... ... ... ... ... Stone Lime. ... 1.86 ... 78-63 ... 0.93 ... None ... 4.30 ... 7.10 ... Trace ... 6-20 ... 0.98 100~00 Mortar. by Volume. 31-23 10.89 1.97 0.61 3.55 1.11 45-99 1.37 3.28 100.00 Iime 1 : Brick 3 parts - A large number of experiments on different samples of ground-up brick and various samples of lime, etc., have shown that it is a safe guide, in determining the volume of the materials from their weight, to increase the weight of lime found in the analysis by one-fourth in order to raise the lime (CaO) obtained to the relative quantity of conmcrcial lime, on the assumption that the commercial lime originally contained 80 per cent.of pure oxide of calcium. The correction from weight to volume is then made by again increasing the weight by one-fourth. The following will illustrate the method : Equal volumes of stone-lime and of air-dry broken brick weighed as follows : Lime ... ..I ... 17.38 grammes per 18.5 C.C. Brick 21.13 ,, 9 , 9 , ... ... ... (1) To convert weight of commercial lime to equal volume of broken brick, add one quarter of the weight of lime found to itself, thus : 17-38 + 4.34 = 21-72. (2) By analysis, this lime contained 78.63 per cent. of real CaO, and a mortar made with this lime on analysis gave 10.89 per cent. of CaO ; therefore, to convert CaO in mortar into terms of commercial lime, for practical purposes add one quarter of the weight of CaO found to that quantity.Thus, CaO in mortar 10.89 per cent. + 2.72 = 13.61 commercial lime. (3) By No. 1, 13.61 + 3.4 = 17.0 of CaO by volume. (4j The ground-brick used in making the mortar (Table 111.) contained 6 per cent. of matters soluble in weak acid ; therefore, to the weight of brick-grit actually found add 6 per cent., i.e., sand and grit (brick), 45.99 (45.99 x 0.06 = 2.76) = 48.75. (5) Lime to brick by volume : 17 : 49, or 1 : 3 nearly.THE ANALYST. 201 I-lc In t io IL of IVc iy IL t to Vo lzme ( Cen~en t-LWoy t u r ). Equal volumes of washed and dried sand and of Portland cement of specific gravity 3.15 weighed 21.7 grammes and 19.3 grammes respectively. Therefore, the weight of ceme’nt found must be raised by one-eighth to equal the s‘and by volume.Average Portland cement will contain from 17 to 20 per cent. of soluble silica. An average of 18 per cent. may therefore be taken, on which assumption the soluble silica formed may be calculated into terms of cement. Thus the 3-25 per cent. of soluble silica found in Sample No. 1, Table IV., would equal 18 per cent., or 19.25 per cent. corrected for volume. The sand and grit equalled 67.34 per cent. ; therefore the ratio of cement to sand was 1 : 3.5. I n sample No. 2 of the same table the soluble silica was 2.5 = 13.9 per cent. of cement = 15.6 by volume ; the sand, etc., was 70.77 per cent. ; the ratio consequently was 1 : 4.5. Sample No. 3 showed a ratio of 1 : 3.5, No. 4 of 1 : C-6, and No. 5 of 1 : 4.8, the average being 1 : 4.4. The samples were stated to be from cement-mortars, made with 1 of cement to 4 of sand.Doubtless the difference is due to unequal mixing. Absoqhou of CO, after Mortar is n~acle. The crushed brick (see Table I.), including some of the silica, iron oxide, and alumina, would amount to 48 per cent., or 51.77 per cent., including 3.74 per cent. of -carbonate of lime found on analysis to be present in the brick. The commercial lime used contained 3-22 per cent. of carbonate of lime, so that the above 16.06 per -cent. would contain 0.52 per cent. These together will account for 4.26 per cent. of the carbonate of lime in the quantity found in the above analysis, showing that only 0.21 per cent. of carbonate of lime was formed between the times when the mortar was made and analysed.,4 ? d y t icn I Methods. Various suggestions have been made as to the best means of more or less rapidly arriving at a conclusion as to the quality of a mortar. Our own experience is against the adoption of any short cuts. However strong one’s individual opinion may be, the evidence is incomplete unless the work is thoroughly done. I t may be interesting here to shortly recite the outlines of the method adopted by us in these examinations. First, the sample, having been thoroughly well broken up and mixed, is placed in a suitable bottle, from which 10 grariimes are weighed in a platinum dish and placed on the water-bath for the estimation of moisture, the drying being con- tinued in the usual way until no further loss is found. Objections may be made to the adoption of this system, in so far as it may be assumed that carbonic acid will be absorbed by the inortar during the process of drying ; but a large number of experiments have shown that such absorption, if any, makes a difference so little in degree that it obviously falls within the limits of the allowable quantity in good samples of mortar..I further portion, weighing 10 grarnmes, is placed in a beaker, stirred up with 10 per cent. hydrochloric acid, and allowed to stand for one minute, when the fluid is decanted, and with it all the fine earthy matter held in suspension. This process is repeated until the supernatant water a t the end of one minute is clehr. The cleaned, washed sand and grit or broken brick is then dried and the weight ascertained. The earthy matter is filtered from the washings and202 THE ANALYST.weighed; a known portion of the filtrate is taken for the estimation of the silica, iron, alumina, and lime, the latter being weighed as snlphate. The sample taken for moisture after weighing is ignited at a dull red heat, insufficient to decompose the carbonate, and the loss on ignition so found recorded. The ignited mortar is then treated with a small quantity of water to completely hydrate the lime, dried at 220" Fahr. and weighed. The loss on ignition is thus obtained. If found necessary, the carbonic acid may be again taken on the dried mortar as a control. I t is obvious that the analysis may be more or less complete according to the character of the information required. The appended tables, Nos.IV. to VII., contain the results of the analyses of some typical samples analysed by us. Table No. IV. shows the results of the analyses of five samples of cement mortar. Table No. V. shows the results of the analyses of three samples of bad mortar. Table No. VI. shows the results of partial analyses of fifteen samples of very bad mortar; in these the analyses were carried only far enough to show that all the samples contain excessive quantities o€ earthy matter and old mortar ; and also that they were deficient in freshly burnt lime. I n contrast with these, Table No. VII. shows the result of the partial analyses of a sample of good mortar taken from a public building in course of erection. In all the following tables the results are stated in percentages.TABLE IV. Analyses of Samples of Cement-nzoytai-. Moisture, water of hydration, etc. ... ... ... ... Lime (CaO) ... _.. ... ,, carbonate ... ... ,, sulphate . . I ... Iron oxide and alumina ... Soluble silica .. . ..- ... Earthy matter . . . ... Loss of ignition ... Sand and grit ... ... KO. 1. 7.50 11 -80 2.86 0.20 4.35 3.25 0.61 2-09 67-34 No. 2. -~ 6.12 10-87 2.86 0.30 3.75 2.50 0.64 2-19 70-77 Total ... ... ... I 100~00 I 100.00 No. 3. 7-72 11-97 1-04 0.99 4 *OO 3.25 0.96 2.42 67.65 100.00 Batio of Cement to S m d , etc. Calculated on the Soluble Silica. 1 : 3.5 ... 1 : 4.5 ... 1 : 3.5 ... 1 : 5.6 1 : 2.7 ... 1 : 3.0 ... 1 : 2.9 . 1 : 3.0 Calculated on the Lime. No. 4. -____ 7.26 9.20 1-87 0.84 4-95 2.00 0.85 2 -50 70.53 100~00 ... ... No. 5. 9-68 11.24 1-45 0-71 4.00 2-25 0-70 2-02 67-95 LOO~OO 1 : 4.8 1 : 3.0 The average total lime in cement may be taken as 60 per cent.; therefore, the lime found, including that carbonated, may be corrected to volume of cement thus :THE ANALYST. 203 Sample No, 1-CaO = 11-8 + 1.6 carbonated = 13.4 = 22.3 of cement ; add one-eighth for correction to volume = 25.1 vols. of cement to 67.34 of sand, or a ratio of 1 : 2.7. I t will be noticed, however, that the calculation of cement from the lime found is unsafe, as the mortar might be sophisticated with lime, and therefore not cement- mortar. TABLE V. Bar1 Linle-7no1’tCl 1’s. The soluble silica is the only reliable indicator. No. 1. No. 2. No. 3, Moisture, water ol hydration ... ... ... ... Lime (CaO) ... ... ... ... ... . .. ,, carbonate ... ,, sulphate ... ... ... ... ... ... Sand, grit, broken brick, etc. ... ... . . . ... Earthy matter ... ... ... ... ... ... Loss on ignition ... ... ... ... . . . ... ... ... ... ... . . . Iron oxide and alumina ... ... . . . ... Soluble silica ... ... ... ... ... ... 17.1 5 -9 8.9 1.8 51-5 1.6 0.9 7.4 4.9 21.1 6.0 8.4 1.7 46 a 3 1.4 0.7 10-4 4.0 15-1 6.2 8.0 2.0 53.4 1.5 0.7 8.1 5.0 100.0 ~~ ... ... ... Total ... 100.0 100.0 Commercial lime (CaO) to sand and grit, etc., by volume $ 7 ,, to all other matters by volume 1 to 5.5 1 to 8-3 1 to5.5 1 to 8-1 TABLE VI. Partial Analyses of very Inferior iwortars, I No. 1. No. 2. No. 3. No. 4. No. 5 . No. 6. No. 7. Moisture . . . . . . . . . . . . Lime (0) . . . . . . . . . . . . Lime carbonate . . . .. . . . . Sand, grit, etc. . . . . . . . . . Earthy matter . . . . . . . . . Iron oxide, alumina, and soluble silica 3-13 7-48 12-61 58-90 8-44 3.75 3-61 8-72 13.18 54.85 7-39 2-90 3.42 5.68 15.45 57.14 8.68 3.00 2-80 7.71 11-36 58-76 7-57 4-50 2-79 6-11 15.79 59-09 7-66 3 ‘30 3-00 6.00 14-66 55.36 9-94 2 -60 3-22 6-73 16-34 55.84 9-27 3-80 Commercial lime (CnO) of 80% to a11 other matters of volume . . . . . . Commercial lime (CaO) of all other matters by volume . . . . . . 1 to 5.0 1 to7-6 1 to 4.2 1 to 6.4 1 to4.a 1 to 7‘4 1 to 6.4 1 to 10.2 1 to 6.1 1 to 9.5 1 to 5.9 1 to 9.7 1 to 5.3 1 to 8.5 No. 8. No. 9. No. 10. No. 11. No. 12. No. 15. No. 13. 7-97 10.29 8 ‘63 54.27 8 70 3.70 1 to 3.3 1 to 5.0 No. 14. 3.1 5 8’34 16.70 50’35 10-41 4-20 1 to 3.8 1 to 6.7 3.87 9.97 11-25 57.00 8.10 4-50 10.28 9 .oo 11.13 50.96 8-78 3.60 4,64 7 5 0 15.11 50.35 9 -30 3 -68 12-01 8.86 55.27 8 *63 4-15 3 -93 7-63 15-80 50.60 8-78 11-70 6’32 5-96 20‘95 52‘05 8-23 3.30 Moisture .. . . . . . . . Lime (CaO) . . . . . . Lime carbonate . . . . . . Sand, grit, etc. . . . . . . Earthy matter . . . . . . Iron oxide, alumina, and soluble silica . . . . . . 3 -80 Commercial lime (CaO) of 80% to sand, grit, broken brick, etc., by volome ... Commercial lime (CnO) of 80% of all other matters by volume . . . . . . 1 to 3% 1 to 5.5 1 to 3.9 1 t o 6 9 1 to 2.9 1 to 4.4 1 t o 5 5 1 to 9-4 1 to4-1 1 to 7’2204 THE ANALYST. TABLE VII. San~ple of Good Moytar taken fyont a PzLblic Building in Cowse of Eyectio?i. Moisture ... ... ... ... ... _.. 17.84 Lime carbonate ...... ... ... 0.97 Lime (CaO) ... ... ... ... ... 14.43 Sand, grit, etc. ... ... ... ... 59.15 Earthy matter ... ... ... ... ... 1 -05 Iron oxide, alumina, and soluble silica.. . .. 3.75 9 , I ? to all other matters (dry), 1 to 3.0. ... ... Commercial lime (of 80 per cent. CaO) to sand, grit, etc., by volume, 1 to 2.6. DISCUSSION. Tho PRESIDENT said that it was seldom the Society had the pleasure of Sir Charles A. Cameron’s presence at their meetings, and he was sure he only echoed the sentiment of all members present in asking Sir Charles to open the discussion. Sir CHARLES A. CANERON said he wits afraid he could not add anything to the very valuable information that had been laid before the Society by the authors of this paper. He occasionally had specimens of cement submitted to him which, although apparently having a correct composition-according to what was laid down in the text-books-nevertheless would not adhere to the surface of bricks.As a matter of fact, disputes were constantly arising in connection with cement, mortar, and concrete, and there was a very large field open to workers in the directionof obtaining informa- tion which would enable such disputes to be settled on a scientific basis, In Ireland he did not think it was customary to use ground bricks in place of sand to such an extent as appeared to be the case in England. €Ie believed the authors had mentioned the case of a mortar in which the propor- tion of lime to sand was as low as 1 : 9. He had himself once examined a sample containing almost as much sand, viz., 86 per cent.MY. ALLEN said that one problem which he had been called upon to solve was how much road-sweepings a particular saiiiple of mortar contained, and what was ihe proportion of c L clean, sharp sand.” Road-sweepings seemed to be a very indefinite article, and he thought that if the authors could indicate how to ascertain the quantity present, it would be of great service t o others as well as to himself. I t seemed to him, if he had understood that part of the paper correctly, that i t was a little questionable whether it was fair to deduce the amount of cement in a, cement iiiortar from the amount of soluble silica. This surely must be a very variable quantity . There was no doubt that the Society was very much indebted to anyone bringing forward figures on such a difficult subject, as they would at least afford something like a basis for further investigations.Mr. BODMER remarked that where broken bricks were used in substitution for sand, the by-laws, although providing for the proper grinding up of the bricks, did not specify distinctly that they should be well burnt. Badly-burnt bricks might beTHE ANALYST. 205 used, and in that case the amount of earthy matter present would be considerable. He thought it desirable that either the use of bricks should be altogether prohibited, or that some more definite limit should be laid down as to their employment. The proportion of quicklime contained in the lime used was also a matter upon which disputes often arose, but it was hardly possible to suggest any definite standard, for in some kinds of liine which were really very good for mortar-making the percent- age of actual quicklime was comparatively low.Mr. JOHN HUGHES said that the by-laws of the London County Council in regard to the composition of inortar were far too vague. Nothing is mentioned respecting the quality of the lime, except that it should be ‘‘ freshly burnt,’’ its rich- ness in CaO and soluble silica is entirely omitted, as well as its weight per cubic foot, which may vary considerably. The sand must be sharp and clean, ‘‘ without earthy matter,” but there is no definition of what constitutes earthy matter. I n making mortar it is usual to specify quantities by measure rather than by weight, consequently the respective amounts of lime and sand, or substitutes for sand, must vary in proportion to their gravity.Therefore mortar, though made according to the strict reading of the by-laws, may contain as little as 10 parts of lime (CaO) by weight in every 100 parts of the perfectly dry mortar. Thus, taking a cubic foot of gray lime containing 80 per cent. CaO, and weighing (according to Hurst’s “Architectural Hand-book ”) 44 lbs., and 3 cubic feet of clean sand weighing 100 lbs. per cubic foot, we have a mixture in the dry state which contains only 10-23 CaO in every 100 parts by weight. On the other hand, if a substitute for sand, such as broken brick, having a less gravity, be used, the percentage of CaO in the inortar would be increased. Some years ago he devoted considerable time to the examination of old inortar obtained from numerous old abbeys and castles, and the results of the analyses were published in I’h Builder during the years 1892 and 1893.These analyses cor- roborated Mr. Bodmer’s observation, that the percentage of actual quicklime was really no criterion of the quality of the mortar. The lime rapidly becomes converted into carbona%e, especially in the smoky atmosphere of towns, and in the case of good building-lime the CaO is associated with soluble silica in the same form as it exists in Portland cement, so that the total lime in its various combinations, rather than the caustic lime alone, should be considered before condemning a mortar. He would mention that, according to his researches, the average amount of caustic liine in ancient mortar did not; exceed 0.5 per cent. Further, within certain limits the actual percentage of total lime was no reliable indication of the quality of the mortar.Thus, the mortar from Rochester Castle (of which only the keep remains), contains as much as 28-67 CaO, while that from Tintern Abbey, in Monniouthshire (which was remarkable from the fact that the four gable ends were still standing), contains only 18.84 CaO per cent. The mortar from the leaning tower of Caerphilly Castle, in Glamorganshire, contains as little as 13.49, associated, however, with 9.85 of soluble silica. He could not agree with Mr. Dibdin in calculating the probable amount of cement present in a mortar from the figures for soluble silica. Limestones contain varying quantities of gelatinous or hydrated silica, which aftvr calcination forms a natural206 THE ANALYST.cement, and it is to the presence of this cement that the durability of ancient mortar largely depends. Greystone lime contains 9 per cent. of this soluble silica ; Aberthaw lime contains as much as 15, while the best Portland cement contains not more than from 20 to 22 ; consequently limestones are suitable for making mortar in proportion to their richness in this so-called soluble silica. In conclusion he would say that some of the best and most durable of these old mortars contained as much as 4 to 5 per cent. of oxide of iron and alumina. Mr. B. E. R. NEWLANDS said he presumed this paper was intended to refer only to cases occurring in those districts in which the by-laws referred to had been adopted; but there were districts where the by-laws had not been adopted, and a still greater number where they had not been enforced.I n Manchester, and other large towns, mortar was manufactured as an industry by the Corporation, and this mortar was generally made with the cinders and clinkers from the Corporation’s destructors. This mortar-which was sold to the general public by the Authorities-would yield very different analytical results from the mortars dealt with in the paper. Mortar made with furnace clinker was also used to a considerable extent in the Metropolitan area, most frequently, perhaps, in the case of buildings erected by work’s proprietors, whose furnaces supplied the clinker ; and this mortar, although of a very high standard as far as hardness and setting power were concerned, would not satisfy the tests given in the paper.Dr. M. A. ADAMS said, that from the local experience he had gained in the midst of the cement district, where there was an abundance of materials for making lime from both white and gray chalk, he could confirm the remark made by Mr. Hughes, that alumina was often a somewhat important constituent oE commercial lime. It was customary in his neighbourhood to look upon the lime made from gray chalk (which contained a large proportion of silicates and 3 or 4 per cent. of alumina) as almost equal in quality to Portland cement. Certainly, it was a fact well-known to all practical builders in the district, that they could use far less of such lime than was required if they employed lime made from the upper layers of the chalk, which was nearly pure calcium carbonate.Mr. DIBDIN said that he and his colleague congratulated themselves on having raised such an interesting discussion. He sincerely hoped that the paper would be the forerunner of several others on the same and kindred subjects. Mr. Newlands was perfectly correct in his remarks as to the scope of the paper. The question had been dealt with entirely as under the by-laws relating to London. As a matter of fact, these by-laws contained the only statement or definition of mortar having legal weight of which he was aware. If they were wrong, it was without doubt desirable that they should be amended as soon as possible, but as they existed, a considerable amount of work had been done under them, and it was just as well that they should be thoroughly understood.The subject, taken in its industrial aspect and as ranging over the ground of all kinds of mortar, both ancient and modern, was of course a very large one, a’nd to treat it exhaustively would require a great deal more than the hour or so available at oneTHE ANALYST. 207 of the Society’s meetings, and he and his colleague looked upon this paper rather as an index for pointing out that a large amount of valuable work could be done by those who took up the subject in detail. With regard to the adulteration of mortar, it was seldom that a sample was found which really complied with the specification contained in the by-laws, a common adulterant, in London at any rate, being dust-bin refuse.Mr. Allen had asked for information as to the best mode of estimating road- sweepings. In many cases road-sweepings consisted largely of sharp sand mixed with organic matter. The only way to deal with them was to separate the organic from the mineral matter and estimate them in the ordinary way. Of course quite a cursory observation would indicate whether the organic matter was in the from of horse-dung or the like. With regard to Mr. Bodmer’s remarks, he did not think much difficulty would be found in dif‘ferentiating between properly burnt earthy matter and clay that had merely been warmed up. The by-laws appeared to be perfectly definite in their references to the ballast or bricks that might be used in inakiiig mortar. They stated that burnt ballast or broken brick might be substituted for sand or grit. Now, earthy matter that had merely been warmed could not properly be described as ‘‘ burnt ballast,” and unless a brick had been fired-and properly fired-it could not, according to his (Mr. Ilibdin’s) idea, be regarded as coming within the meaning of the term “brick,” any more than partially heated chalk could be regarded as lime. Mr. Hughes had remarked that the amount of lime present was no criterion of the quality of a mortar, and had referred to the mortar of Tintern Abbey as con- taining 16 per cent. of lime. Now, assuming 16 per cent. of caustic lime to be equivalent to 20 per cent. of commercial lime, and adding one-fourth to correct for the difference in specific gravity between the lime and sand, the volumetric propor- tion of lime to sand worked out in this case to 1:3, or exactly the. same as laid down in the by-laws. With regard to clinker-mortars, these were not comprised in the present paper, which dealt only with good brick, grit, or clean, sharp sand, and lime or Portland cement. I n the case of mortar made with other materials, other data must be obtained as a basis of calculation.

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DOI:10.1039/AN8962100197

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年代:1896

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THE ANALYST. 207 NOTZ ON " DRAWN '' OR EXHAUSTED CARAWAYS. BY BERNARDYER, DSc., AND J. F. H. GILBARD. (Read at the Meeting, May 6 , 1896.) ATTENTION was recently directed to the adulteration of caraway " seeds " by the admixture of " drawn " or exhausted caraways (ic., " seeds " from which the flavouring matter had been extracted). We obtained a specimen of " drawn )) cara- ways and examined it, together with genuine caraways of good quality.208 a, 42 r;l 6 A: 0 3 2 “0 gi5 03 .:g m r;; r( 42 rn 4 2 Genuine Dutch caraways . 12-3 1-9 “Drawn” caraways ... 6.9 0.1 9 , 9 9 9 , 11.3 1.5 THE ANALYST. M U h U c; “ w cd 4 - 2 c s w rd 8 % a 4 -- s: 25 ::x g 2 .- M i 3 p 5 r= g 2: - & I 6B 3 2 4 2 a s 5 g 4a @ 2 , 2 g Z $ 5 -T --------c___ 20.4 11% 5.8 2.1 3.7 0-3 19.5 9.5 6.3 2.1 4.2 0.4 l G .1 12.0 6.3 2.2 4.1 0.4 The ‘( approximate volatile oil ” was obtained in the same manner as described by us in a previous paper on ginger (ANALYST, xviii., 1W), viz., by taking the flask containing the ether extract and drying it on a shelf over the water-oven until it loses only a milligramme or so in ten minutes. It is then dried to constancy inside the water-oven to furnish the ‘(fixed ether extract,” and the difference is called “ volatile essential oil.” From the above figures it will be noticed that the effect of exhausting the caraways has been to cause almost the total disappearance of the volatile oil upon which the aroma of the seeds depends, while the fixed ether extract ’ I has decreased by one-fifth. The other items, with the exception of the moisture, remain practically the same. In our opinion, therefore, samples showing a low percentage of (’ volatile essential oil ” and ( ( fixed ether extract,” and containing, if unground, many dark seeds, should be viewed with suspicion.

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DOI:10.1039/AN8962100207

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年代:1896

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208 THE ANALYST. LEAD I N A SAMPLE OF CANADIAN CHEESE. BY F. W. STODDART, F.I.C. (Rend at the Neetiizg, May 6, 1896.) THIS specimen of cheese was of a brand largely imported into England from Canada, and which in this particular instance was complained of by the importers as being very dark in the interior. On examination, it was found that the coloration, which to the eye exactly resembled moulding, was due, not to the presence of fungi, as might at first have been supposed, but to an amorphous powder, which consisted of lead dust. The specimen examined contained an average quantity of la grains of metallic lead per lb. of cheese, distributed in veins, and giving the cheese a marbled appearance. My first supposition was that the lead had been added with the object of pro- ducing that blue appearance which was generally admired in cheese, but I wasTHE ANALYST. 209 informed by the shippers that this particular cheese was sold as a white cheese, and that the coloration would materially depreciate its value. Regarding the form in which the addition was made, I could only conclude that the lead had been added in the form of actual lead dust. It occurred to me that it might have been added in the forin of lead sulphide, but I was unable to detect any traces of sulphides, and could not imagine any chemical change which would result in the reduction of the sulphide to the metallic form actually present in the cheese. It was, however, very difficult to get the lead out sufficiently pure to make quite certain, on account of its intimate incorporation with the fatty inaterial of the cheese,

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年代:1896

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THE ANALYST. 209 NOTE OK THE ANALYSIS OF CREAM OF TARTAR. BY ALFRED H. XLLEN. A SOMEWHAT curious error occurs in my proposed process for the analysis of cream of tartar published in the July nuniber of THE ANALYST. The facts are correctly stated in the earlier part of the paper, but in method 2 CL, on page 180, mistakes occur which would be liable to cause confusion if left uncorrected. The following is an amended description of the process in question :- I n a pure sample the measure of acid required will be exactly equal to that of the alkali consumed in process 1. The presence of calcium tartrate in the sample does not affect the results. Each C.C. of t7cficie1zcy of acid represents 0.36 per cent. of calcium sulphate (CaSO,), or 0.72 per cent. of acid potassium sulphate (KHSO,).Any excess of acid required points to the presence of neutral potassium tartrate, each C.C. of difference representing 0-60 per cent. of that salt. If the titrated liquid be treated with barium chloride, the weight of the precipitate of barium sulphate will give the means of directly determining the proportion of calcium or potassium sulphate. The use of decinormal alkali for the titration of the original sample of cream of tartar involves the use of what inay be considered an inconveniently large volume of the standard solution. If seminormal alkali be employed instead of decinormal, and 3.763 gramlnes be taken for analysis, each C.C. used for neutralization will represent 2.5 per cent. of acid potassium tartrate. I n this case the titration will require much care, but the results will be quite accurate enough for most purposes. Titrate the filtrate with decinorinal hydrochloric acid and methyl-orange.

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DOI:10.1039/AN896210209a

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年代:1896

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210 THE ANALYST. ORGANIC ANALYSIS. Determination of the Heat of Bromination in Oils. H. W. Wiley. (Jour. Anzer. Chem. Soc., 1896, xviii., 378-385.)-After speaking in general terms on the value of Hehner and Mitchell’s process (ANALYST, xx., 146), Dr. Wiley describes some modifications which he has adopted with the view of rendering it more easy of appli- cation. The bromine is dissolved in the chloroform in the proportion of 1 volumeTHE ANALYST. 211 in 4, and this solution used instead of the liquid bromine. The bromine solution is placed in an Erlenmeyer flask with a side tubulure near the top, on which is fixed a rubber bulb. Through the stopper of the flask a pipette is passed and made air- tight, and the bromine solution can then be readily blown up into the pipette by compressing the bulb.Another modification consists in dissolving a larger amount of the fat in chloroform and taking aliquot portions of the solution, thus allowing several deter- minations to be made on the same sample. The calorimeter employed is a tube about 40 cm. in length and 1; cm. in internal diameter, fitted air-tight by means of a rubber cork into a drying jar with a side tubulure. To secure insulation of the inner tube, air is withdrawn from the drying flask through the side tubulure. The author has found carbon tetrachloride preferable to chloroform as a solvent, by reason of its greater stability and higher boiling-point. The rise of temperature, however, is slightly less than in the case of chloroform solutions. As to the ratio between the rise of temperature and the Hiibl number, stress is laid on the point that the factor 5.5 is not universally applicable, but that the factor must be determined separately for every system of apparatus and solvent employed.* W.J. S. Determination of the Acidity of Pyroligneous Products. Scheurer-Kestner. (C'omptes ~ c i z d m , cxxii., p. 619.)-Among the bodies associated with acetic acid in crude pyroligneous acid are phenols and acetic ethers, notably methyl acetate (con- taining 15 to 17 per cent. of the total acid), and it therefore becomes necessary both to remove the phenols, which vitiate the results of titration, and to determine the amount of acid in tlie methyl acetate, since this latter escapes observation when the ordinary method is pursued. Both. objects may be effected by distillation over phosphoric acid, which retains the phenols and decomposes the methyl acetate.Twenty grammes of the crude acid are distilled in a flask along with 50 graiiimes of phosphoric acid (15" B., S. G. 1.116), until merely a small quantity of liquid remains. An addition of 20 C.C. of water is then made and the distillation continued, this operation being repeated once more, When the distillate which comes over is nearly neutral to test-paper, it is ready for titration by sodium hydroxide, phenol- phthalein being the most suitable indicator. This method gives results 10 per cent. below those obtained by the ordinary process, the error in the latter being due to the reaction of the phenols. I t is also suitable for application to acetate of iron or alumina, being, in fact, a development c.s. of the Fresenius method for the analysis of calcium acetate. Technical Analysis of Asphaltum. S. P. Sadtler. (Jozu-. Praizkhz Inst., 1895 [5], p. 383.j-Criticising the method described by Linton (ANALYST, xx., p. 41), Sadtler proposes to discard the use of turpentine, and replace the petroleum spirit by acetone for extracting the petrolene, retaining chloroform as a solvent for the asphalt ene. * This was specially stated in Meesrs. Hehner and Mitchell's paper.212 THE ANALYST. One to two grammes of the asphalt are carefully mixed with some 10 grammes of fine white sand in a Gooch crucible containing an asbestos filter, the apparatus having been previously dried at 100" C. till constant. The drying is repeated with the asphalt, and the decrease in weight is designated " moisture and loss at IOO"." The crucible and contents are inserted in a small percolator contained in a larger one connected with a flask holding the acetone, and with a vertical condenser. Heat is applied (a sand-bath being preferred) and extraction continued until the loss has decreased to 0.5-1 milligramme per hour, a result generally attained at the end of some twelve hours, The loss by this extraction is considered as " petrolene." Chloro- form is then substituted for the acetone, and the extraction of the " asphaltene " eff'ected in about eight hours.The residual matter in the crucible represents organic non-bitumen and mineral substances ; the latter may be estimated by incineration and weighing.c. s. Volumetric determination of Uric Acid. G. Deniges. (Bzdl. Soc. Pharnt. BordeuzLz, 1896, 75; through Aim. de Chi7n. AnnZyt., I. [8], 148.)-The method proposed is by throwing down the uric acid by an excess of cuprous hyposulphite, and titrating the copper by the cyanide method. The following reagents are required : 1. 160 grammes anhydrous sodium carbonate, 2. 100 ,, crystallised sodium hyposulphite, 100 , , sodium potassium tartrate, 3. 40 ,, pure crystallized copper sulphate, 10 drops sulphurio acid of 66" B. (S. G. 1.842), each made up to 1,000 granimes of solution by distilled water. The phosphates of the alkaline earths are thrown down from 100 C.C. of urine by 10 C.C. of solution No. 1, and the filtrate mixed with 40 C.C. of No. 2 and 10 C.C.of No. 3. The supernatant liquid is decanted at the end of 10 minutes and aspirated through a flat filter, making sure that sufticient of the reagent is added to bring down the whole of the precipitable matter. The filter must be well washed repeatedly with a thin stream of water to collect the whole of the precipitate at the centre, and left to drain after each operation. When diabetic urine is under examination, washing must be continued until all the sugar is removed. The precipitate is then washed with boiling water into a porcelain capsule, and hydrochloric acid (0-5 to 1-5 c.c.) added, followed by sodium hypobromite, or bromine water, drop by drop, until the copper urate is dissolved, and the liquid becomes permanently yellow, or yellow-green. The solution which should not exceed 40 c.c., is heated to boiling, 10 C.C.of ammonia added, and whilst the boiling is brisk and uninterrupted, Zscinormal potassium cyanide solution added, drop by drop. Towards the end point t i e boiling must be kept brisk and the reagent added only every third or fourth second, until the blue coloration of the solution disappears. The amount of copper is calculated by the formula : (IL - 0.1) x 0.594 x 0.00635 n being the number of C.C. of cyanide solution.THE ANALYST. 213 To arrive at the uric acid per litre of urine-making allowance for the dilution due to the sodium carbonate solution-the factor 0.01 is employed, the formula being : The titration may be falsified by the presence of the sarkinic bases, adenine or hypoxanthine.These may be detected by the precipitate given with copper hypo- sulphite after neutralisation with potash, and in such case these bases must be thrown down from neutral solution by the mixture of solutions 2 and 3, the 10 C.C. of sodium carbonate being added subsequently, and the operation conducted as described. C. S. (12 - O . l ) O . l + ( I b - O ~ l > O * O l . Estimation of Fusel-oil in Rectified Spirit. .A. Stutzer and R. Maul. (Zeit. anal. Chem., 1896, xxxv., pp. 159-163.)--The determination by Rose's process of the aniount of fusel-oil in rectified spirit requires inuch greater care than in the case of brandy, etc. I n 1890 Stutzer and Reitmair showed that fusel-oil inay be concentrated by fractional distillation, and that in distilling 1 litre of spirit con- taining 0.5 per cent.of fusel-oil only the last 50 C.C. of the distillate contained that constituent ( h A r J Y s r r , xv., pp. 189 and 203). In testing rectified spirit, one litre is left in contact with 100 grammes of dry potash in a large flask for several hours. It is then distilled over a brine bath until three-fourths have passed over. The receiver is changed and distillation continued so long as alcohol distils. The flask is then cooled, 250 C.C. of water added to the potash, and 100 C.C. distilled over a parafin bath. This distillate is added to the last alcoholic distillate, the mixture diluted to 500 c.c., the specific gravity accurately determined at 15" C., and the liquid brought to 30 per cent. by volume of alcohol. For the shaking apparatus the authors use one similar to that of Windisch graduated in 0-02 c.c., and allowing of a reading of 0.01 c.c., since the divisions are 1.2 milligrammes apart.Each fresh apparatus should be standardized with pure spirit (30 per cent. by volume). This may be most easily obtained by distilling the best commercial rectified spirit made alkaline with potash, rejecting the first 20 per cent. and last GO per cent., and using the intermediate fraction. In making an estimation chloroform is first introduced, so that the lower meniscus at 20" C. corresponds with the lowest mark. 250 C.C. at 15" C. of the alcohol, brought to 30 per cent. by volume, are then introduced, and 2-5 C.C. of sulphuric acid of sp. gr. 1.286 added. The stoppered apparatus is then well shaken (about 150 times), and finally placed in a cylinder of water maintained at 20" C.After about an hour the liquids will have separated, and the increase in volume of the chloroform can be read off.' The following examples are given : Height. Difference. c. c. C.C. ... ... 20.59 - Addition of 0.01 per cent. ainyl alcohol _.. ... 20-63 0.04 2 , 0.10 ), $ 2 ... ... 21-03 044 ,, 0.20 ,, 9 9 ... ... 21.48 0.89 Hence it appears that a difference in volume of 0.1 C.C. corresponds to 0.022472 per cent. amyl alcohol in 30 per cent. spirit, or 0-075 per cent. in 100 per cent. spirit, With pure alcohol . . . ... ...214 TEE ANALYST. and thus, by concentrating the amyl alcohol, as described above, 0.005 per cent. by volume in 100 per cent. spirit can be accurately determined. C.A. M. Determination of Albumin in Urine. G. Mercier. (AWL de Clcimie Analyt. i., 125.)-The most satisfactory results are obtained when the quantity of albumin does not exceed 100 to 150 milligrammes. I t therefore becomes necessary, when the percentage of albumin is high, to take only a small quantity (10 C.C. or less) of urine, and to make up to 50 C.C. with distilled water. A frequent result of this dilution is imperfect coagulation, and the escape of portions of the albumin along with the filtrate. This defect may be remedied by restoring to the solution the proper balance of saline matter by adding about 1 gramme of sodium chloride. I n such cases the coaguluni must be thoroughly washed with boiling distilled water until no trace of chloride can be detected in the washings.c. s. Estimation of Para-Sulphanilic Acid. Karl Brenzinger. (Zeit. nng. Chem., 1896, 131-133.)-This method depends on the decomposition of the sulpho group by means of bromine, and the subsequent estimation of the liberated sulphuric acid. It is necessary to avoid a large excess of bromine, as otherwise the barium sulphate precipitate will be contaminated by sulpho acids. I n the experiments with pure water-free para-sulphanilic acid, one-tenth of a molecule (17.3 granimes) was dissolved in a litre of water, and the solution, if alkaline, made slightly acid with hydrochloric acid. Portions of 100 C.C. were then treated with saturated bromine water, uiitil after standing fifteen or twenty minutes there was zt slight excess of bromine when they were tested with potassium iodide starch-paper.After twenty minutes pure soda solution was added to slightly alkaline reaction to remove the slight excess of bromine, the liquids filtered, and the sulphuric acid in the filtrates determined in the usual manner. Warming the liquid before filtration was advantageous, but not essential, in the case of pure para-sulphanilic acid, but where metanilic acid was present the precipitation, filtration, and washing had all to be done hot. I n impure samples the sulphuric acid was determined first, and the amount deducted from that subsequently obtained after bromination. EXAMPLES. Pure Acid taken. BaYO, found. 13aS0, calculated. Para-sulphanilic Acid. Per cent. 1-73 2.3294 2.330 1.7291 99.95 1-73 2.3250 2-330 1-7253 99-71 IMPURE SAMPLE.1.73 grammes yielded 0.673 gramme BaSO, before bromination. Difference = 1.6528 grainme BaSO, = 79.3 per cent. para-sulphanilic acid, 9 , ,, 2.4402 grammes BaSO, after bromination.THE ANALYST. 315 Experiments made with mixtures of pure metanilic acid and pure para-sulpha- nilic acid gave the following results : Para-sulphanilic Acid added. BaSO, obtained. = Pare-sulphenilic Acid. Per cent. Grammes. Per cent. 0.2 0.0083 0.35 1 -0 0.0305 1.3 5.0 0.1160 4-98 I n three specimens of impure metanilic acid the amount of para-sulphanilic acid found was 4.93, 4-47, and 4.27 per cent. respectively. I n the absence of other compounds, on which nitrites could act, the sum of both acids could be obtained by diazotizing, and the amount of metanilic acid by deducting from this the quantity of para-sulphanilic acid found by the method described above.C. A. M. Estimation of Aniline and Toluidine in presence of small quantities of each other. (Zed. anal. Chem., 1895, xxxiv., 734-740.) -The method described by the authors is an adaptation of Reinhardt's process (Cham. Zeit., xvii., 413), and is based on the fact that aniline forms a tribromo-derivative, while o - and y - toluidine give dibromo-derivatives. Reinhardt's directions are slightly modified, hydrobromic acid being replaced by potassium bromide and hydro- chloric acid, and starch iodide paper used as the indicator. The brominating solution 160.5 is standardized with pure aniline, and the value thus obtained multiplied by 93 gives the toluidine value.When water is absent, one titration will give the amount of the aniline and toluidines in a commercial oil. Where a = weight of oil, x = amount of aniline, t - value of brominating solution standardized on pure aniline, and 2: = No. of C.C. of solution used :- x = 2.3777vt - Im3777a, and a - x gives the amount of toluidine in the oil. When only a small quantity of aniline is present, as in commercial toluidine, the results are too high. In that case, the brominating solution should be Standardized with pure toluidine, and the aniline Or (as is preferable) the solution may be value t obtained by multiplying by standardized with both pure aniline and pure toluidine, and the amount of aniline calculated by the equation P. Dobriner and W. Schranz. 93 160.5: x x-a t T = v where t and T represent the standardization values. I n making a determination, about 150 C.C. of the brominating solution (1 litre = 8 grammes aniline) are used, and the readings taken at 15" C. The test analyses of mixtures quoted are satisfactory. C. A. M. Estimation of Moisture in Aniline and in Ortho- and Para-Toluidines. P. Dobriner and W. Schranz. (Zeit. C L ~ . C ~ Z C ~ . , 1895, xxxiv., 740-742.)-Rein- hardt's method (see preceding abstract) is applied to this estimation by brominating216 THE ANALYST. equal weights of the moist and dried substances, and calculating the percentage of moisture F by the formula (2. : b=(lOO -F) : 100. where a = number of C.C. absorbed by the wet substance Treatment with fused potassium carbonate renders aniline and o-toluidine anhydrous, while p-toluidine may be distilled, and the residue, after distilling 10 per cent., taken as dry. C. A. M. 9 9 b= 9 1 I ? ? t dry I 1

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DOI:10.1039/AN8962100210

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年代:1896

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216 THE ANALYST. INORGANIC ANALYSIS. Estimation of Potash by the Carnot Method. Ed. Goutal. (Ann. de C'lhnie Analyt., i., 89-91.)-The following particulars are given of the method as performed at the laboratory of the Ecole Nationale des Mines, under the direction of M. Carnot himself. The reagents are prepared thus : 1. Bismuth C7d0de SoZut.ion.-lOO grammes of bismuth subnitrate dissolved by exactly the necessary amount of hydrochloric acid, and made up to 1 litre with 95 per cent. alcohol. If any turbidity ensues-due to the precipitation of a sub-salt -it should be redissolved by a few drops of hydrochloric acid. 2. Cnfci~im Tlziosdphnte SoZutio1z.-This should contain 200 gramines of the pure crystallized salt per litre. The thiosulphate niust be freshly prepared, exhibit no tinge of yellow, and be properly crystallized.3. Iodine Solutioii.-A standard solution containing 26.96 grammes of pure iodine dissolved by the aid of about 40 grammes of pure potassium iodide. 4. Sotlimz Tliiosiilpliute Sollition.-Standardized to correspond to the iodine solution--i.c., containing 52.64 grammes of the crystallized salt per litre. The substance is dissolved in 8 C.C. of water, and the solution (which may include a trace of free hydrochloric acid) should not contain more than 700 rnilligrammes of potash. To obtain an average sample, in the case of more or less homogeneous complex bodies, it is better to dissolve froin 20 to 30 grammes in the proportion of 1 gramme 0.f substance to 8 C.C. of water. A mixture of the reagents is then prepared by adding together in the following order : 20 C.C.of the alcoholic bismuth solution, 20 C.C. of the calcium thiosulphate solution, and 200 C.C. of 95 per cent. alcohol; this should produce a perfectly clear liquid. When the substance contains less than 300 rriilligrammes of potash, one half the foregoing quantities of bismuth and thiosulphate solutions, and 150 C.C. of alcohol will be sufficient. The reagent is poured into the potash solution, and, after vigorous agitation left at rest for half an hour, by which time the precipitate of double thiosulphate of bismuth and potassium will have fallen. On decanting the liquid, the precipitate is thrown on to a filter, and carefully washed with 95 per cent. alcohol. Quick filtra- tion is desirable, bnt the aspirator need not be resorted to if the paper is good and filters freely.The double salt is dissolved by washing with cold water on the filter, and, afterTHE ANALYST. 217 the addition of a little fresh starch paste and 2 or 3 C.C. of hydrochloric acid, iodine solution is added from a burette until a dark brownish-green coloration (passing sud- denly from pale yellow) is produced. Should the end-point have been overstepped, the sodium thiosulphate solution is used. Each C.C. of iodine solution corresponds to 1 centigramme of potash. The method is very exact and rapid, but requires the observance of the following precautions : The calcium thiosulphate must be freshly prepared ; the bismuth solution must contain exactly 100 grammes of subnitrate per litre; 95 per cent.alcohol alone should be used, as the precipitate is partly soluble in weaker spirit ; and the mixed solution must be slightly acid. I t is also important that the thiosulphate should not be in excess as’compared with the bismuth, or a portion of it will be thrown down by the alcohol and vitiate the result. If, however, all the conditions be observed, a careful operator will be able to determine with ease potash existing indifferently as chloride, nitrate, carbonate, phosphate, or even sulphate, without the necessity for the previous removal of such associated bases as soda, lithia, ammonia, lime, magnesia, iron or manganese oxides, etc. c. s. Losche’s Process for the Estimation of Potassium. H. Haefcke. ( C I J L C ~ . Zeit., 1896, xx., 88.j-This process (ANALYST, xsi., Ell), really devised by Mehns, is by no means original.A precisely identical method was described by De Roode in 1895; and one essential feature of it-the removal of sodium sulphate from a pre- cipitate of potassium platinochloride by the action of aininoniuni chloride solution- is due to Finkener, who published it in 1867. The latter noted that the ammonium chloride decomposed up to 5 per cent. of the potassium salt, especially in presence of hydrochloric acid, even at ordinary temperatures, and during one hour’s action ; so that in Lindo and Gladding’s method-a standard commercial process in America -the solution is treated for twenty-four hours before use with the potassium platino- chloride, in order to saturate it, although Breyer and Schweitzer have pointed out that this device is not sufficient to prevent further action.The claim that pOt&SSiZl7II, sulphate is converted into the double platinum salt by washing with ammonium chloride under conditions that leave the corresponding sodium coinpound unattacked has not been substantiated, and, indeed, seems incredible. I n short, the process cannot be considered reliable. El. H. L. The Estimation of Potassium. (1) A. Prager, (2) R. Ruer, ( 3 ) E. Bauer. (CIuxvL. Zeit., 1896, xx., 269 and 2iO.)-In making use of the process that Fresenius has described as most suitable when the potassium in the sample exists only as sulphate, Prager considers that the purity of the precipitated platinum salt can only be relied on when it is obtained in the crystalline condition.Nven extracted filter- papers contain matter soluble in 80 per cent. alcohol and hot water; and it is absolutely necessary, therefore, to treat thein with these liquids before determining their original weight. The author’s process is as follows : The sulphuric acid is removed with the smallest possible excess of barium (Fresenius prefers an asbestos filter.)218 THE ANALYST. chloride, and after filtration the liquid is made up to 75 c.c., the platinum solution added, and the whole evaporated on a water-bath, which is not allowed to boil. Directly crystals appear on the surface, the liquid is cooled, and, after removal of the deposit, evaporated slowly down to 5 C.C. I t is again cooled, diluted with 20 C.C. of 96 per cent. alcohol, stirred well, and allowed to stand for a time.The whole of the precipitate is then brought on the prepared filter by,means of 80 per cent. spirit, and it is finally dried in a well-ventilated oven at 110" C. The double chloride should afterwards be treated with a small quantity of cold water to test its purity. The factor 0.19308 is to be used to convert the platinochloride into potassium oxide. Ruer finds that the ordinary practice in many potassium works of heating the double salt for only twenty minutes to 130" C. gives a product which may for most practical purposes be considered dry and fit for weighing. It nevertheless contains sufficient moisture to render the usual factor of 0.3056 (to calculate it into potassium chloride) too high. Fresenius has endorsed this figure ; but his experiments were carried out on precipitates dried for at least twelve hours, and he insists on the necessity of heating till constant weight, To avoid this loss of time, the author suggests drying the platinum salt at 130" for half an hour, and making use of the factor 0.304, otherwise the results, although perfectly concordant, are uniformly 0.5 per cent. above the correct amount.Bauer suggests that, instead of drying and weighing the precipitate on the filter, it should be dissolved in hot water, and the solution allowed to run through the paper into a tared platinum basin. The filtrate is then evaporated and dried at 120" C. This improvement obviates the danger of the platinochloride being partially reduced by careless drying, does away with the unsatisfactory process of using a weighed filter-paper, and removes any insoluble matter in the precipitate, which may be due either to traces of barium or to the presence of platinous chloride in the reagent.I n this manner also the platinum residues are kept pure and free from organic matter. F. H. L. Examination of the Methods for the Determination of Manganese in Iron and Steel. (Chem. Zeit., 1896, xx., 285 and 337.)-The author has re-investigated six different processes for this purpose, testing them on crucible, Besserner, and Martin steel, and on Thomas cast-iron. Care was taken that the borings should be uniform in composition by drilling the samples only at one spot, and by preparing at one operation sufficient material for all the tests. The gravi- metric processes employed were : (1) Estimation as manganese sulphide : (2) pre- cipitation by bromine, and weighing as Mn,O, ; (3) Ford's process.The volumetric methods were: (4) Volhard's; (5) precipitation of the iron with sodium sulphate followed by titration of the manganese ; (6) Hampe's chlorate process. All the samples were examined six times by each method, and the results were almost identical in every case, showing a perfectly satisfactory agreement with the theoretical amount of manganese present. As regards the time occupied in carrying them out, (5) and (6) are the quickest, consuming only 1i t o 14 hours, the others requiiing longer, up to three hours in the case of (1). L. Rurup.THE ANALYST. 2 19 (5) is in use in Krupp's laboratory, and is carried out as follows : 4 grammes of the borings are dissolved in 75 C.C.of 1.2 nitric and 10 C.C. of hydrochloric acid; the solution is poured into a litre flask, sodium carbonate added till the liquid is just rendered faintly opaque, then 1-13 grammes of sodium sulphate is introduced, the whole made up to the mark, and allowed to stand without heating till the precipitate has subsided. I t is filtered into a 750 C.C. flask, boiled with 15 grammes of zinc sulphate, and titrated with permanganate. F. H. L. A Gravimetric Method of Estimating Phosphoric Acid as Ammonium Phospho-molybdate. (Jow. Amer. Chenz. s'oc., 1896, xviii., 23- 27.)-To the solution of phosphoric acid 25 C.C. of strong ammonia (0.900 specific gravity) are added, and then nitric acid (1.42 specific gravity) to acid reaction.The beaker is placed in a water-bath maintained at 50" C., and the ordinary 10 per cent. acid molybdate solution added at the rate of about three drops per second, with constant stirring, until about 10 C.C. in excess. After remaining ten minutes in the bath, the liquid is filtered through a weighed filter-paper, previously dried at 105" C., and the filtrate tested with more molybdate solution. The precipitate is washed three times by decantation, and three times on the paper with dilute nitric acid (1 : loo), and once with distilled water. The paper and contents are drained cn filter-paper, and then dried at 105" C., until the weight becomes constant. For drying at this temperature, the author found a water-bath surrounded with dilute glycerine (1.160 specific gravity), boiling at 110" C., the most reliable means.As thus obtained, the yellow precipitate is of very uniform composition, and free from separated molybdic oxide or iron. Multiplication by the factor 0.0376 gives the amount of phosphoric acid it contains. The results obtained with a solution of pure microcosmic salt, containing 0-5 grammes in 50 c.c., were 34.06 to 34.10 per cent. of phosphorus pentoxide by this method, and 34-05 to 34-05 per cent. by precipitakion with magnesia mixture. Four determinations were made by each method. To test the applicability of the method to the determination of very small amounts, the above solution was diluted to one-tenth : T. S. Gladding. Taken. Yellow Salt Obtained. P,O, Obtained. P,O, Theoretical.1. 10 C.C. ... 0.091 ... 0.00342 ... 0.00340i 2- 1 Y Y ... 0-010 ... 0.00037 ... 0.00034 Comparative tests with a number of fertilizers also gave closely agreeing results, the phosphoric acid being as follows : Official Method. Per cent. 28-80 2.63 12.03 28.30 15-64 15.04 15.19 29-16 ... ... ... ... ... ... ... ... ... ... ... ... ... ... . . . Kew Method. Per cent. ... 28.87 ... 2-70 ... 12.00 ... 28-33 ... 15-70 ... 15-00 ... 15.23 ... 29.23220 THE ANALYST. I n each case 0.250 gramme was used for precipitation, and an excess of about 10 C.C. (not more) of the molybdate solution added. C. A. M. A Modified Ammonium Molybdate Solution. A. L. Winton. (Jour. A4nzci.. Chent. SOC., 1896, xviii., pp. 445-446.)-The following formula is recommended for the preparation of a solution containing the same proportion of molybdic acid and free nitric acid as the solution of Fresenius, but having 15 grammes more ainmoniuni nitrate in 50 C.C.: 1. Dissolve 1,000 gran?.mes of molybdic acid in 4,160 C.C. of a mixture of one part of concentrated ammonia (sp. gr. 0.90) and two of water. 2. Dissolve 5,300 grammes of ammonium nitrate in a mixture of 6,250 C.C. of concentrated nitric acid (sp. gr. 1.4) and 3,090 C.C. of water. Add I. to 11. slowly with constant stirring, and decant the clear liquid after standing for a few days in a warm place. The use of this solution obviates the necessity for the separate addition of ammonium nitrate, which is often employed to facilitate the separation of the molybdic precipitate and to shorten the time of digestion.C. A. M. Analysis of a Mixture of Chlorides, Chlorates, and Perchlorates. Ad. Carnot. (Comptes r e w h s , cxxii., p. 452.)-Perchlorates are found along with chlorides and chlorates in the products of the calcination of chlorates. Hypochlorites are only produced in the cold or by wet methods; but in such cases no perchlorates are formed, nor can the latter be reduced by the usual reagents in solution, dry heat being necessary to accomplish this result. In analysing such mixtures, the chlorides and chlorates are estimated first, by titrating one portion of the solution for the chlorides with argentic nitrate and ammonium thiocyanate, and the other part for the total chlorine after reduction of the chlorates by the aid of ferrous sulphate; or, as an alternative method, both titrations can be performed on the same liquid, the chlorides first-with sodium arseniate as indicator in preference to potassium chromate, which would interfere with the subsequent reaction-and then the total chlorine after reduction of the chlorates. Finally, the perchlorates are determined by heating the powdered substance, mixed with four or five times its weight of purified quartz-sand, in a platinum crucible, the mixture being covered with a layer of the same sand 1 or 2 c.111.deep. The bottom of the crucible is kept at a red heat for about twenty to thirty minutes, and this is sufficient to completely reduce the chlorates and perchlorates, volatiliza- tion of the chloride being prevented by the condensing effect of the upper layer of sand.An aqueous solution is then made, the total chlorides titrated as before, and the perchlorate estimated by difference. c. s.THE ANALYST. 221 Volumetric Determination of Mixtures of Chlorides, Hypochlorites and Chlorates. Ad. Carnot. (Cowzptes rendus, cxxii., 449.)-These mixtures are met with in the products resulting from the action of chlorine on the hydroxides of the alkalis or alkaline earths, chlorate being always present in bleaching powder in small quantities, increasing with the age of the product, especially when the lime used contained carbona,te. The same salts are also formed when chloride of sodium is subjected to electrolysis. The hypo- chlorite is determined by titration with sodium arsenite, which does not reduce the chlorate in neutral or alkaline solution, the end point being gauged by testing a drop of the solution with potassium iodide and starch.The liquid, which now only contains the chlorates and chlorides, is acidified with a little sulphuric acid and heated to nearly 100" C., with about twenty times as much ferrous ammonium sulphate as the amount of chlorate suspected. Then a solution of 5 C.C. of sulphuric acid in 15 C.C. of water is added drop by drop, and, after being left to cool in the flask (closed to prevent access of air), the excess of ferrous salt is titrated by permanganate. This allows the amount of chlorate to be calculated, and, after decolorizing the solution by a little ferrous sulphate, the total chlorine is determined by adding a measured quantity of argentic nitrate, and titrating back the excess by means of ammonium thiocyanate.The end point is indicated by the formation of red ferric thiocyanate, which occurs as soon as all the silver salt has entered into combination. A single solution suffices for the estimation of all three substances. c. s. The Iodometric Estimation of Selenious and Selenic Acids. F. A. Goo& and A. W Peirce. (Zeit. f. An. ChC?72., xi., 249.) This is an improvement on methods previously published by one of the authors (Gooch and Reynolds, h i t . j : An. Cliem., x., 248) in which selenious acid is heated with acidulated potassium iodide, and the iodine estimated volumetrically in the distillate and residue. To avoid the double estimation of iodine the authors now propose a method based on a reaction previously employed for the estimation of chlorates (Gooch and Smith, Aiize?-.Jourii. Sci. [Sill.], xlii,, 220). If an acid solution of potassium iodide be heated with c,)'cess of arsenic acid, all the iodine is liberated, a corresponding proportion of arsenic acid being reduced to arsenious acid. By prolonged heating the iodine is completely volatilized, and the residue, after being made alkaline, is titrated with standard iodine, of which the quantity required is a measure of the arsenious acid formed. If in addition to arsenic acid a more easily reducible substance is present, such as a chlorate, or selenious acid, it gets reduced in preference to the arsenic acid, and consequently less arsenious acid is formed and less iodine is required in the final titration.The difference between the iodine solution used up under these circurn- stances, and what would have been required had arsenic acid alone been initially present, indicates the quantity of the chlorate or selenious acid. The practical details are as follows :-A weighed portion of the selenious acid is introduced into a 300 C.C. Erlenmeyer flask along with a known weight of potassium iodide (which should be in excess of what is theoretically required) in EL solution of222 THE ANALYST. wl iicli the strength in terms of arsenious acid has been accurately ascertained. Finally, a solution containing about 2 grammes of acid potassium arsenate and 20 C.C. of 50 per cent. sulphuric acid is added. To prevent loss by spurting a short calcium chloride tube is allowed to rest with its wide end in the neck of the flask, and to avoid bumping some pieces of pipe-clay are put into the liquid, which is then boiled until the original volume of about 100 C.C.is reduced to 35. 20 C.C. concen- trated solution of sodium bicarbonate, and some starch solution are then added and the titration with normal iodine performed. The difference between the amount thus required, and the larger volunie which would have been needed in the absence of selenious acid (due to the arsenic acid alone being reduced), indicates the proportion of selenious acid. To estimate selenic acid it must first be reduced to selenious acid, which is best done by means of potassium bromide and sulphuric acid as previously shown (Zeit. f. An. Cizem., x., 253) the use of hydrochloric acid being inadmissible on account of the arsenic trichloride which would be afterwards formed.NOTE BY ABsTRACToR.-The authors appear only to have tried the process on the pure substances. C. H. C. The residue is cooled and neutralized with caustic potash. Acidimetric Determination of Zinc. L. L. de Koninck. (Jfon. Scknt., 1896, lBO.)-Working with a one-fifth normal solution of zinc potassium sulphate, and pure titrated potash, to test the rival opinions of Barthe and Lescceur on the composition of the precipitate, the author finds that this varies with the temperature, being 7Zn0, 2ZnS0, when the operation is performed in the cold, and 17Zn0,3ZnS04 at 65" C. At 100" C. the decomposition of the zinc salt is complete within 1 or 2 per cent.; the final reaction is slow, the phenolphthalein losing its colour gradually. An excess of alkali is necessary to produce complete decomposition, and the only satis- factory way of titrating this back is by operating at boiling temperature and checking the colour by the aid of a duplicate solution containing no phenolphthalein. C. S. The method, pursued in this manner, is exact, but is not suitable for ores. The Quantitative Determination of Hydrogen. E. D. Campbell and E. B. Hart. (Amel.. Chem. JOUY., 1896, xviii., 294-298.)-1n 1894 F. C. Phillips (Amer. Chem. Jour., xvi., 256) proposed to determine hydrogen by absorption with dry palladious chloride, but was unable to obtain satisfactory results. The authors have devised the following method, based on the same principle, but using a solution of palladious chloride.This is prepared by dissolving 5 grammes of palladium-wire in 30 C.C. of hydrochloric acid, to which has been added 1.2 C.C. of nitric acid. The solution is evaporated just to dryness on the water-bath, and the residue dissolved by warming with 5 C.C. of hydrochloric acid (specific gravity 1.20j, and 20 to 25 C.C. of water. This solution, when diluted to 750 C.C. gives a nearly neutral solution con- taining about 1 per cent. of palladious chloride.THE ANALYST. 223 The pipette employed is the ordinary Hempel absorption-pipette, which is made so as to be readily detachable from its stand. I n making an estimation, the solution is first introduced into the pipette, then the gas to be analyscd, from which every- thing except hydrogen, paraffins, and nitrogen has been removed, and finally sufficient water to completely fill the capillary.The pipette is then disconnected, the top being first closed with a pinch-cock, and placed in a hot water-bath for two hours, which is sufficient time for complete absorption, unless the amount of hydrogen exceeds 65 c.c., or the pipette has been previously used. After the pipette has been used for the absorption of about 100 c.c., the remaining solution should be evaporated just to dryness on the water-bath, 5 to 6 C.C. of hydrochloric acid, 4 to 5 C.C. of nitric acid, and a little water added, and the evaporation repeated. The dry palladious chloride is dissolved by adding 2 C.C. of hydrochloric acid, and warming with a small amount of water, and the whole diluted to the original volume and returned to the stock-bottle.The experiments summarized below show the accuracy of the method, all volumes of gas being reduced to standard temperature and pressure : Volumes taken. Strength of Palladious Residue, Hydrogen, C.C. Kitrogen, c. c. Chloride Solution. Time of Heating. c. c. 18-7 80.3 1 per cent. To 50" C., overnight. 80.3 53.7 23.8 9 9 9 , Water-bath, 90 minutes. 23-8 1.07 52-23 ,, 9 , 9 , 1 , 53-62 1-27 70-8 2 per cent. Water- bath, overnight . 70.84 From these and other experiments the author concludes that a 2 per cent. solution of palladious chloride has very little advantage over a 1 per cent. solution. With strongly acid solutions absorption was retarded. C. A. M. The Estimation of Pyrrhotite in Pyrites Ores.E. F. Cone. (Jour. ilmcr. C h ~ m . SOC., 1896, xviii., 404-406.)-1n the manufacture of sulphuric acid from pyrites ores, it is found impossible to burn off the greater part of sulphur present in the form of pyrrhotite (Fe,S,), which is often a constituent of American ores. The estimation of pyrrhotite sulphur is therefore of considerable importance, and for this purpose the author describes the following process, which is based on the fact that Fe;S, is magnetic, while pyrites is non-magnetic. The ground ore is passed through a sixty- mesh sieve, and 13-74 grammes weighed out and spread on glazed paper. A magnet is then passed through the powder, and the magnetic portions separated. This is repeated several times, the separated portion ground in an agate mortar, and the sulphur estimated gravimetrically by oxidation with nitric and bromo-hydrochloric acids. The weight of barium sulphate obtained in grammes is the percentage of sulphur present as pyrrhotite.The method is accurate to within one-fifth per cent., but the ore must not be finer than will pass through a sixty-mesh sieve, or the results will be unreliable. Examples :224 THE ANALYST. A SAMPLE OF ORE CONTAINING PYRRHOTITR. Total sulphur . . . ... 35-07 Sulphur present as Fe,S, 24-14 Per cent. ,, iron ... ... 57-50 Iron 9 , Fe,S, 36-96 Oxygen as Fe;;O, ... 4-26 1 , 9 , Fe S, 9-34 Insoluble mrttter ... 2.i8 Iron , l Fe,O, 11.20 Copper ... ... 0.25 Sulphur l l Fe S, 10.68 99.86 A small proportion of this ore was added to pyrites containing no pyrrhotite, so This mixture was Some of the results obtained that the mixture contained 1.20 per cent.of sulphur as Fe,S,. analysed for pyrrhotite sulphur, using different weights. were : Per cent. Sulphur Grammes. 133aS0, as Fe,S,. 5.00 gave 0.4120 - - 1.13 9 7 1.13 13.74 1.13 - 9 1 1-18 25.00 2.15iO - - - C. A. M. CORRESPONDENCE. THE EXAMINATION OF WATER. To tJrc Editor .f THE ANALYST. SIR,-In order, if possible, to bring bacteriologists and chemists into line as to the relative value of their respective methods of water-examination, it is necessary to keep this subject constantly before the profession. I, therefore, offer no apology for drawing attention to some recent remarks made by Dr. Klein in the course of his Harben Lectures, as reported in the Tinzes of June 9, 7896. They are as follows : '' The chances of finding the typhoid bacillus in ordinary cases, where it was only present in small quantities, were exceediiyly ~ e n z o i e . I t was like looking for a needle in a rick of hay. Statements, therefore, such as were repeatedly made, to the effect that certain samples of water, milk, or other materials did not contain the typhoid bacillus were qiiite rnlrceless. The only m f e rule was to regard any fluids in which the presence of sewage organisms has been demonstrated with suspicion, whether the typhoid bacillus was found or not." Here, then, we have an emphatic declaration by one of our leading bacteriologists that the outcry against the chemical analysis of water, because it could not detect the presence of pathogenic organisms, was a vain and foolish one. The only question now requiring consideration in connection with this matter as I pointed out in my note read before our Society in March, 1895, is the following : '' How can sewage pollution be most certainly detected, chemically or biologically ?', I have given my answer in the note mentioned above, and should now like, with your permission, to invite discussion in your pages on this most important point, as it seems to me high time that this vexed question should be settled one way or another in the interest of the public as well as of the profession. The italics are my own. Yours, etc., A. DUFI;~~.

ISSN:0003-2654    

DOI:10.1039/AN8962100216

出版商:RSC    

年代:1896

数据来源: RSC