« PoprzedniaDalej »
Oct. 20, 1876.
New Method for Ascertaining Anthracen.
is decomposed by ignition with charcoal powder. The preparation of bromide of potassium and the bromides of iron is conveniently combined with the manufacture of bromine. Since 1867 Franck condenses bromine in a set of three Woolff's bottles, the first of which, slightly cooled, receives liquid bromine, whilst the second contains bromide of potassium or ferrous bromide, and the third potash-lye or iron-turnings. The chloriferous bromine vapours escaping from the first slightly cooled receiver pass through the solution of bromide and are freed from their chlorine, in the place of which bromine escapes from the bromides and arrives in a pure state into the ironturnings or the potash-lye contained in the third bottle, in which pure bromides are at once obtained.
We have already mentioned that a large proportion of bromide of potassium is obtained from the ferroso-ferric bromide. The manufacturers of bromide of potassium are not under the necessity of preparing the iron compound themselves from condensed bromine. It is obtained at the Stassfurt bromine works, and is sold in the form of a paste containing from 65 to 70 per cent of bromine. As it can be packed in vessels of stoneware and tinned iron and even in wooden casks, it is the most convenient form for the carriage of bromine, which, in the free liquid state, is difficult to pack and dangerous to convey.
(To be continued).
The precipitate produced by arsine in the water solution of mercuric cyanide is very unstable, decomposing in a few hours into Hg and arsenious and hydrocyanic acids at the ordinary temperature. The precipitate is so finely divided that it passes completely through filter-paper. Stibine appears to be a still more energetic reducing-agent on mercuric cyanide than phosphine or arsine; a rapid stream of stibine (SbH3), prepared from (Sb2Zn3), producing a precipitate of metallic mercury in either aqueous or alcoholic solutions. W. R. H.
Royal College of Chemistry.
NEW METHOD FOR ASCERTAINING
THE EXACT QUANTITY OF PURE ANTHRACEN
By MEISTER, LUCIUS & BRÜNING.
THE experience gained during the last few years with regard to anthracen testing has induced us to abolish our old test of October, 1873, and the appendix of 1874, and to issue a new and improved method, as follows:
Take 1 grm. of anthracen, place it in a flask with condenser of 500 c.c. capacity, add to it 45 c.c. of glacial acetic acid, and heat to ebullition. To this solution (which is kept boiling) add, drop by drop, a solution of 15 grms. of chromic acid in 10 c.c. of glacial acetic acid and 10 c.c. The addition of the chromic solution should occupy two hours; after which the liquid is to be kept boiling for two hours longer, four hours being required to complete the oxidation.
ACTION OF PHOSPHINE (PH3) ON MERCURIC of water.
WHEN pure phosphine is passed into a solution of HgCy2
It is so sensitive to light that it was found impossible to dry it, even in vacuo, without change of colour in the superficial portions. After drying for thirty hours in vacuo over oil of vitriol, a sample had a surface-colour greenish black, the under part being still yellow. Quantitative analysis shows it to contain Hg, P, Cy, and H.
When heated in contact with the atmosphere it ignites at about 90° C., undergoing a kind of smouldering combustion, a residue of phosphoric acid, mercury, and some difficultly combustible carbonaceous matter containing nitrogen, (probably "para-cyanogen ") being left. When heated in tube a little cyanogen gas and a phosphuretted hydrogen are given off, a residue of mercury and phosphoric acid, with carbonaceous matter, remaining.
The substance is oxidised by nitric acid, but dilute HCI and sulphuric acid do not seem to affect it. Carbon, hydrogen, and mercury combustions have given the following figures:-
Royal College of Chemistry.
ARSINE AND MERCURIC CYANIDE.
The flask with its contents is to be kept standing for twelve hours, then mixed with 400 c.c. cold water,* and again kept standing for another three hours.
The precipitated anthraquinon is now collected on a filter, and washed first with pure water, then with boiling dilute alkaline solution, and finally with pure hot water. The quinon is now washed from the filter into a dish, and dried at 100° C. It is then mixed in the same dish with ten times its weight of fuming sulphuric acid of 68° Baumé (sp. gr. 1·88), and heated to 100° C. for ten minutes on a water-bath. The quinon solution thus obtained is poured into a flat dish, and kept for twelve hours in a damp place to absorb water.
Then add 200 c.c. of cold water to the contents of the dish, collect the precipitated quinon on a filter, and wash first with pure water, then with boiling alkaline solution, and finally with pure hot water.
The anthraquinon is now placed in a dish, dried at 100° C., and weighed. After volatilising the quinon by heating the dish, it is weighed, with the particles of coal and the ash.
The difference between the two weights gives the weight of anthraquinon obtained, and it is to be calculated in the usual manner into anthracen.
Hoechst, a. M., October, 1876.
Prize in Industrial Hygiene.-An offer of a medal in connection with this subject has been made by Mr. Benjamin Shaw, and has been accepted by the Council of the Society of Arts. The medal will be of the value of £20, and will be awarded every fifth year. The terms of the offer are as follows:-" For any discovery, invention, or newly-devised method for obviating or materially diminishing any risk to life, limb, or health, incidental to any industrial occupation, and not previously capable of being so obviated or diminished by any known and practically available means.' The first award will be made in May, 1877. The latest date for receiving communications
A PRECIPITATE is also produced by arsine (AsH3) in alco-will be March 31, 1877.
precipitation of the anthraquinon, and the correction formerly made
The increased quantity of water added ensures the complete is no longer necessary.
Practical Chemistry in the University of Virginia.
NOTES OF WORK BY STUDENTS OF
LABORATORY OF THE UNIVERSITY OF VIRGINIA.
Communicated by J. W. MALLET, Professor of General and Applied Chemistry in the University. (Continued from p. 149.)
(2.) Chemical Examination of Füh-ling (Lycoperdon solidum) from China. By J. L. KELLER, of Charlottesville, Virginia.
Among a number of interesting specimens which Mr. Justus Eck, of London, was kind enough to present, some two or three years ago, to the laboratory collections of this University, was one of this curious material, accompanied by the following extract in reference to it from the late Mr. D. Hanbury's "Notes on Chinese Materia Medica :"
"Füh-ling; Pachyma cocos, Fries (Fungi); Lycoperdon solidum, Gronovius; Pé-fo-linn, Cleyer (Med. Sin., No. 189), Tafarinov (Cat. Med. Sin., pp. 2-23); Puntsaon; Indian Bread; or Tuckahoe. A very large remarkable substance resembling ponderous rounded tubers having a rough blackish brown bark-like exterior, and consisting internally of a compact mass of considerable hardness, varying in colour from cinnamon brown to pure white. These tuberiform bodies, which in weight vary from a few ounces up to several pounds, are found attached to the roots of fir trees, or sometimes buried in the ground of localities where firs no longer grow. They occur in South Carolina,* in some of the northern and western provinces of China, and in Japan. Their true nature is sufficiently perplexing. The older writers considered them to be a sort of China root (Smilax), a supposition which their outward appearance certainly favours, but which is immediately negatived when we find them to contain no trace of starch. Loureiro and Endlicher are content to describe them as tubers found upon the roots of fir trees. Other botanists have placed them among fungi; Gronovius and Walter in the genus Lycoperdon; Schweinitz in Scleroticum; Okur and Fries in Pachyma. The latest observations on the subject are some which were submitted to the Linnean Society by Mr. F. Currey and myself last year (1861) and published in the Linnean Transactions. The opinion there expressed is that these tuber-like bodies are an altered state of the root of the tree, probably occasioned by the presence of a fungus, the mycelium of which traverses, disintegrates, or even obliterates the wood and bark. This mycelium appears under the microscope in the form of fine threads usually more or less mixed with bodies of irregular shape, somewhat resembling starch granules, but which are apparently cells of the woody tissue in a more or less advanced state of disease and distortion. Nothing is known of the more developed form of the fungus represented by the mycelium. The American Füh-ling has been examined chemically by Professor Ellett, of South Carolina College, who has stated it to consist entirely of pure pectine of Braconnot, but I think its composition deserves some further investigation. I find that the pure white internal substance (which is quite insipid and inodorous) is very slightly soluble in cold rectified spirit and in cold water, and not more so when boiled in water, the solution in each case yielding a flocculent precipitate with acetate of lead. When boiled in a weak solution of carbonate of soda the substance dissolves rather more freely, and the solution affords a scanty gelatinous precipitate (pectic acid) when
They are by no means peculiar to this State. I have seen specimens found at various points from Virginia to Alabama on the Atlantic side of the country, and, as will be seen by the quotation from Report of the Department of Agriculture, they extend as far west as
CHEMICAL NEWS, Oct. 20, 1876.
| treated with an acid, or (pectate of lime) with a solution of lime. In China the Füh-ling is made into edible cakes, which are frequently sold in the streets; it is also reported medicinal in a variety of disorders. In America it has also been used as an article of food, whence the name Indian bread."
The Report of the U.S. Department of Agriculture for 1870 (p. 423), in an article upon materials used as food by the North American Indians, has the following notice of this substance :
"Tuckahoe or Indian Bread (Lycoperdon solidum).—Two specimens of this fungus are in the collection of the Department of Agriculture-one from Nottoway Co., Virginia (fig. 1, plate 10), and the other from Leroy, Kansas (fig. 2, plate 10). These singular fungous growths are subterranean and parasitic on the roots of large trees. A piece of root is often inclosed in the mass. The form is irregularly globose, about the size of a man's head. It is very rugous and filled with cracks; the colour externally is ashy black, in the interior white or nearly so, of a starchy appearance, very firm, and breaks into irregular masses. The Kansas specimen is rounded in shape, with a black, rough exterior, and a white and compact interior. When broken it has the appearance of a mass of dried dough, full of fissures and very granular. Booth and Morfit's Cyclopædia of Chemistry gives the following under the article of Picquotaine,' a highly nutritious plant used as food by Indians. It results from a disease of the Psoralea esculenta. Its composition is as follows:Nitrogenous matter, 4'09; mineral substances, 1·61; starch, 81.80+ water, 12'50." The following remarks relative to the Tuckahoe are furnished by Dr. John Torrey: It was first brought to the notice of the public by Dr. Clayton, who sent it to Gronovius under the name of Lycoperdon solidum and as such described it in the Flora Virginica about one hundred andtwenty years ago. Next it was described by the late Dr. von Schweinitz, in his "Synopsis of the Fungi of North Carolina," under the Macbride, of Charleston, South Carolina, sent to the name of Scleroticum cocos. About the same time Dr. Linnean Society of London his observations on that fungus. Without being aware of having been anticipated about the year 1819, under the name of Scleroticum giganby Schweinitz I described it in the New York Repository teum. I gave also a chemical analysis of it, showing that it is chiefly composed of a singular substance which scribed the same principle, which he called pectine. In I named sclerotine. Braconnot some years after this dethe Synopsis Fungorum of Fries, the fungus is called Pachyma cocos. In the Proceedings of the Linnean Society of London is an account by Rev. M. J. Berkeley of a large subterranean fungus that is sold as food in the streets of Shanghai, undoubtedly the same as the Tuckahoe."
And in the Report of the same Department for 1871 (P. 98) occurs the following from R. T. Brown, Chemist to the Department:
"Tuckahoe or Indian Bread.-This curious fungus (Scleroticum giganteum) is quite common in many parts of the Southern States, where it is frequently used as an article of food.* To determine its nutritive value a specimen from Columbia, Virginia, was subjected to careful analysis in this Laboratory, with the following results:"Moisture
*This is certainly an over strong way of stating the facts. Specimens of the material in question are not very rare, and they are
Practical Chemistry in the University of Virginia.
"This analysis does not sustain the high reputation of | correctness of the opinion of Messrs. Hanbury and Currey this substance as a food material."
The substance received from Mr. Eck being from China, while all the above statements as to chemical composition refer to material from America, and these statements differing so widely from each other, it seemed well to make a new analysis, which was done by Mr. Keller.
The specimen of Chinese Füh-ling examined was kidney-shaped, about 6 inches in longest diameter, and 3 inches in shortest, and weighed about two pounds and a quarter. The rough, brownish black, bark-like exterior was about an eighth of an inch thick, verging gradually into the perfectly white uniform mass inside. The whole was compact and firm, but easily cut with a saw, and the fragments, after removal of the exterior crust, shewed but little toughness and were easily crushed in a pestle and mortar. A sufficient quantity was reduced to fine powder, passed through a sieve, and thoroughly mixed. This powder yielded little soluble matter to either cold or hot water, but was much more freely dissolved by a dilute solution of hydrate or carbonate of sodium, the liquid produced in each case giving a flocculent gelatinous precipitate (corresponding in character to pectic acid) when treated with an acid or alcohol, such precipitate proving excessively difficult to wash. Starch and cane-sugar were carefully tested for, but none could be found.
as to the general nature of the substance, viz., that it represents woody fibre altered by the interpenetration of a fungus mycelium. In the specimen analysed by the Chemist of the Agricultural Department the alteration seems to have been incomplete, leaving a good deal of unchanged cellulose; in the case now under notice the cellulose has nearly disappeared. The very small amount of nitrogen renders the notion of the whole mass being simply an independent and developed fungus very unlikely.
Mr. Keller also made an analysis of the ash, to obtain which about 100 grms. of the substance was incinerated at a very low temperature in porcelain crucibles placed each within another of sheet iron serving as a hot-air bath. The ash was tolerably free from remaining charcoal. Chlorine, carbon dioxide, and silica were determined from the whole amount used; and after dividing the solution into two portions, sulphuric oxide and the alkalies were obtained from the one, and phosphoric oxide, ferric oxide, lime, and magnesia from the other. The analysis afforded :— Crude Ash.
The quantitative analysis was made as follows:Water was determined by prolonged exposure to 110° C.; albuminoid matter was calculated from the amount of nitrogen, determined by combustion with soda lime. For the organic matters soluble in water the powder was exhausted with water by repeated boiling, keeping the flask full of steam so as to exclude air; the liquid rapidly filtered, and evaporated (in a retort exhausted by a Bunsen's pump) to a small bulk. The solution was then divided into two parts, continuing the evaporation of the one to dryness at 100° C., weighing the residue as soon as it ceased to lose moisture, incinerating, and weighing the ash left; while Deduc O equiv. to the other was separately evaporated to dryness, exhausted with dilute alcohol (which took up a little glucose), and the residue dried at 100° C. and weighed; this being burned and the weight of ash plus the previously determined weight of albuminoid matter deducted, the quantity of gum was found by difference. In the dilute alcoholic solution glucose was determined by Fehling's copper solution. The pectous material was dissolved out from what water had left by repeated boiling with a dilute (1 per cent) solution of sodium hydrate, and precipitated by dilute sulphuric acid and alcohol, but it was found to be almost impossible to wash the slimy precipitate, and it could not have been relied upon as unaltered in weight from the original insoluble pectous material, so that this was estimated by difference. The cellulose left undissolved by the sodium hydrate was treated with very dilute sulphuric acid (in the cold and for a short time only), then thoroughly washed with water, thrown on a weighed filter, dried at 100° C., and weighed; after burning the weight of the ash was deducted. The results were:0.87) Org. matter2.98 Sol. in water 0'78) 77.27) Org. matter3.76) Insol. in water
Gum (with a trace of acid)..
These figures, especially if taken in connection with Mr. R. T. Brown's results, are strongly suggestive of the
occasionally eaten by the negroes of the Southern States, but the substance can by no means be said to be common, or commonly used as an article of food. In the analysis there is obviously a little error of statement in reporting elementary nitrogen and accounting for all that remains of 100 per cent in non-nitrogenous material.
The large amount of sand is not caused by want of care in removing the exterior portions of the mass. With a lens sparkling little siliceous grains can be detected on a perfectly clean cut surface of the interior. This again accords with the idea of a fungoid growth pushing its way in a sandy soil into disintegrating woody tissue, and cannot at all be conceived of as a result of simple independent vegetable growth. Part of the large percentage of silica found to be soluble, and perhaps of the iron also, may very likely be also mechanically derived from the soil, but how much we have no means of determining. (To be continued.)
South African International Exhibition, 1877.An International Exhibition will be held in Cape Town in 1877, in a building to be erected for the purpose, by consent of the Colonial Government. It will include manufactures of all kinds. The date fixed for the opening is February 15, and everything intended for the Exhibition must be shipped from London not later than during the first week in December, 1876. should communicate immediately with Mr. Edmund Intending exhibitors Johnson, Commissaire Délégué, at the European Central Offices of the Exhibition, 3, Castle Street, Holborn, London. The Exhibition will be arranged in the following classes-Class 1.-Alimentation. Class 2.-Chemicals, perfumery, medicines, and surgical appliances. Class 3.-Furniture. Class 4.-Fabrics, clothing, watches, jewellery, ornaments, precious stones. Class 5-Means of transport, travelling equipments, harness, saddlery, &c. Class 6.-Hardware, edge tools, cutlery, metal work of all kinds. Class 7.-Machinery, materials, and construction. Class 8.-Agricultural, &c. Class 9.-Science and Education. Class 10.-Miscellaneous.
The Hygienic Congress at Brussels.
THE HYGIENIC CONGRESS AT BRUSSELS.
THE inauguration meeting of the Congrès International d'Hygiène et de Sauvetage took place at the Palais des Académies on the 27th ult., His Majesty the King of the Belgians being present. Lieut.-General Renard welcomed the Foreign Members of the Congress. M. Vervoot then delivered his Inaugural Address.
The Congress was divided into three sections, viz.Hygiene, Saving of Life, Social Economy. The English
Committee was constituted as follows:
President.-Capt. Douglas Galton, C.B., F.R.S. Hygiene.-Presidents, Mr. Edwin Chadwick, C.B., and Dr. Richardson, F.R.S., &c; Vice-Presidents, Dr. Hardwicke and Mr. H. H. Collins; Secretaries, Mr. J. S. Phené and Mr. J. W. Pearse.
Saving of Life.-Presidents, Sir Henry Verney, Bart., and Mr. William Crookes, F.R.S., &c.; Vice-Presidents, Surgeon-Major Pater and Mr. G. M. Cooke; Secretary, Major Burgess.
Social Economy.-President, Mr. John Siltzer; VicePresident, Mr. Willis Bund; Secretary, Mr. John Russell,
The questions discussed in the first section included the following:-"What are the advantages of the distribution of population? Discuss the inconveniences which result of water, and what are the means for conveying it to the centres from taking water from the hydrographic basin. Statethe normal consumption per head of the inhabitants."
"Which is the most practicable system for ridding a town of its fœcal and putrescible matter and of its mud? Indicate the means (a) to purify sewage; (b) to utilise the drainage; (c) to prevent the contamination of watercourses by the refuse from factories; (d) to neutralise the noxious effects of dung-heaps in the proximity of dwellings, and to determine the circumstances which should regulate the choice of disinfectants and antiseptics."
In the second section the fifth question was-"What are the means of preventing explosions and flooding in mines, and of lessening their effects? Indicate the most secure means of lighting mines."
In the third section the first question was-"Determine the best arrangements, from a moral and hygienic point of view, for private dwelling-houses. Describe and examine the situation; the methods of heating, ventilation, and lighting; the means of supplying drinking-water and water for domestic uses; the systems of drainage."
A report on water-supply was read by M. Zimmer. In the discussion which followed the report M. GERARDIN contended that water was good if animals could live in it; that the higher the organisation of the animal life the purer would be the water. He did not consider the quantity of mineral salts had much influence, whilst the presence of organic matter was fatal to the infusoria. Water from different sources ought not to be mixed.
M. VANDENSCHRIEK believed that 200 litres per diem for each individual was an unnecessary quantity. Formerly, only 20 litres were allowed per head, and yet epidemics were not so numerous nor so fatal at that epoch as in the present day.
M. BERGE pointed out (1) that the town of Brussels had a water-supply dating from Joseph II. (2) That it had been proved that organic matters only are hurtful; that it was known that water charged with lime and with chloride of calcium killed the fish; that chemical analysis was necessary to determine the quality of water. (3) That it was not yet proved that the mixing of two good waters was injurious.
With regard to the distribution of water, Captain DOUGLAS GALTON was in favour of constant supply with out cisterns in preference to the intermittent supply by cisterns.
The COUNT TORELLI thought the determination of the quantity of water per head to each inhabitant very difficult, and varied naturally with the climate and the various conditions of the population.
M. VARRRENTRAP pronounced against all waters obtained from the towns themselves.
M. T'SERSTEVENS insisted that water ought to be obtained from places thinly populated; where the soil is barren and the water superabundant.
M. DELUE advocated the periodical inspection of cisterns. The papers on the sewage question included one by Mr. Crookes, who described the A B C process of purifying and utilising sewage.
M. L. Derote, Engineer of Bridges and Roads, on the The programme of the conferences included a paper by
conclusions of the report of the English Rivers Pollution Commissioners, so far as it concerns the oxygenation of contaminated waters; and on the purification of the Senne and the drainage works of the town of Brussels executed under his (M. Derote's) direction.
Full reports on each subject brought before the Congress are being prepared, and will shortly be printed.
The King of the Belgians has offered a prize of 5000 francs to that city, local authority, or private association which shall, by improvements in the dwellings of the working classes effect the greatest reduction of the death rate at the lowest cost. The prize will be awarded at the next International Hygienic Congress, which will probably be held in 1878.
NOTICES OF BOOKS.
Annual Report of T. P. Janes, Commissioner of Agriculture of the State of Georgia for the Year 1875. THIS issue contains a judicious and temperate reply to the sweeping objections often raised against the analysis of soils as of little value in pointing out their properties. We should scarcely, however, give in our adhesion to the view that fluorine, small as are the proportions in which it occurs, is of no value.
A curious instance is given of a soil which appears to have been cropped continuously for about ninety years without ever having been manured. The subsoil was originally very rich in plant-food, but its valuable ingredients have been greatly reduced in quantity.
The cultivation of cotton is considered very unremunerative, and farmers are recommended to turn their attention, in preference, to wool-growing. There is, however, a difficulty in the way: 15 per cent of all the sheep in the State are destroyed by dogs, which in the United States are a greater nuisance than even in Europe.
The Report generally may be pronounced full of valuable matter, but by far the greater portion of this is of an economical rather than of a chemical character.
Sydney City and Suburban Sewage and Health Board: Seventh, Eighth, and Ninth Progress Report of the Board appointed on April 12th, 1875, to inquire into and report as to the best means of disposing of the Sewage of the City of Sydney and its Suburbs. Sydney: Thos. Richards.
WHEREVER mankind congregate in great numbers the sewage question, sooner or later, forces itself upon their attention. Believers in laissez faire may for a short time shut their eyes to polluted streams, and affect not to perceive the evil odours that hover around them. But in the long run erysipelas, typhoid fever, diarrhoea, and perhaps cholera, speak in a language which cannot be misunderstood, and action is taken, but frequently when too late. Rising communities, whether in the British colonies or in the United States, cannot too early set about combatting the inevitable cvil. The longer the needful measures are delayed, the costlier and the less efficient they will prove. Australia has hitherto enjoyed a remarkable immunity from zymotic diseases, but if fever is once introduced
Oct. 20, 1876.
Rose Colour Observed in Chlorate of Potash.
its complete expulsion may not prove easy. The Sydney, authorities do not seem favourably disposed towards irrigation. It must be admitted, on the one hand, that in so comparatively dry a climate as that of Australia this method of dealing with sewage seems more feasible, from an economical point of view, than under the cloudy and drizzling skies of England; but, on the other hand, the danger to health will undoubtedly rise with the average temperature. We scarcely understand the precipitation scheme recommended at Sydney. The material to be employed is the carbonaceous residue from certain shales employed in the manufacture of kerosene oil. We can readily see how this matter might form a useful filter-bed, or how it might be employed as an adjunct in a precipitation process; but we are not aware that it contains any principle capable of acting as a true precipitant.
Practical Manual of Chemical Analysis and Research applied to the Arts and Manufactures." By P. A. BOLLEY and E. KOPP. Second French Edition, revised and enlarged. Translated from the Fourth German Edition, by Dr. L. GAUTIER. Parts 3 and 4. Paris: F. Savy.
THIS Manual is more extensive in its scope than any similar work in the English language. With the exception of purely pharmaceutical products it embraces every class of substances which are likely to fall into the hands of the commercial analyst or the "works-chemist." But as the entire book does not greatly exceed one thousand pages, we need not be surprised if some bodies are disposed of rather briefly, whilst others are treated at a disproportionate length. Thus alcoholic liquids occupy nearly one hundred pages, whilst soils and manureswhich in this country certainly occupy a much larger share of the attention of analytical chemists-take up merely forty-two.. In treating of the determination of phosphoric acid in manures and phosphatic minerals, the authors declare their conviction that of all known methods the molybdic acid process alone is capable of a general application, and yields results really trustworthy. All the other methods described, gravimetric or volumetric, are inexact or very tedious, on account of the presence of iron ör alumina. The authors decide, contrary to the view of Birnbaum and Chojnacki, that nitric acid cannot be safely used as a solvent in the analysis of mineral phosphates, as notable quantities of phosphoric acid remain undissolved in the residue. They recommend hydrochloric acid when the presence of iron in the solution can occasion no difficulty, as when the molybdic method is to be used. In other cases Graham's solvent-sulphuric acid diluted down to 5 per cent of the monohydrate-may be advantageously employed.
For determining "reverted" phosphoric acid in manures they prefer the indirect method-ascertaining the total phosphoric acid insoluble in water, and deducting from this quantity the phosphoric acid insoluble in citrate of
In treating on aræometry the authors strongly recommend Twaddle's hydrometer, in preference to those of Baumé and Beck, so much employed upon the Continent, and which are as devoid of any rational foundation as is the English system of weights and measures.
In the examination of magenta for sugar-an occasional adulteration-it is recommended to withdraw the colouring matter from the solution by means of wool or silk, or to precipitate it with common salt. The sugar then remains in solution, and may be easily recognised, and, if needful, determined.
The directions for the examination of lac-dye are somewhat insufficient. For certain uses, as in dyeing stuffs which require to be hot-pressed, it is very important that lac-dye should contain a minimum of gum-lac, for the approximate estimation of which the authors give no in
"Manuel Pratique d'Essais et de Recherches Chimiques appli
qués aux Arts et a l'Industrie."
structions. In treating of cochineal and indigo no allusion is made to the specific gravity of the samples, the determination of which is an easy and rapid way of detecting mineral impurities, whether accidental or intentional. Light cochineals and indigos may certainly be bad, but heavy ones cannot be good. Flavin appears to have been entirely overlooked, and the extracts of the dyewoods are spoken of merely in the solid state in which they are so often met with on the Continent, and not in the liquid form prevalent in England. The preparation of extracts, we may here observe, is one of the branches of manufacturing chemistry in which England is now not holding her own. Very considerable quantities both of French and American extracts are now used in Lancashire.
The tables showing the reactions of colouring-matters -natural, artificial, and when fixed upon textile fibresare very complete. As regards the coal-tar colours, the authors have in many instances taken the useful precaution of giving the name of the manufacturer, often the only method of identifying the exact substance in question.
The least satisfactory portion of the work is the section on milk, which is altogether out of date, and in which much space is devoted to those deplorable instruments the lactometer and the creamometer.
The book will form a useful addition to the library of reference of the analytical chemist.
ROSE COLOUR OBSERVED IN THE MANUFACTURE OF CHLORATE OF POTASH. To the Editor of the Chemical News. SIR,-The following facts may throw some light upon the origin of the "rose 19 or red-violet colour observed in the course of manufacture of chlorate of potash, as noticed in Dr. Hofmann's "Report" &c. (CHEM. NEWS, vol. xxxiv., P. 139). Nearly all commercial samples of chloride of lime give, when boiled with distilled water, a splendid violet-red solution; on filtering through paper the colour disappears, and the paper is stained brown: if it be removed from the funnel, washed from adhering chloride of lime, and moistened with pure strong hydrochloric acid, the stain disappears, and a yellow solution is formed, which gives the characteristic iron-reactions with ferrocyanide and sulphocyanide of potassium. The purple solution may be obtained clear by subsidence, and may then be drawn off with a pipette; it may be evaporated nearly to dryness on the water-bath without decomposition, but on applying a somewhat stronger heat, to drive off the last traces of moisture, the coloured compound is decomposed, and the mass acquires a brown tinge.
If alcohol be added to the clear coloured solution a blue shade is first developed, and afterwards the colour gradually fades into a faint brown.
To determine the question of the presence of manganese, one drop of the coloured solution was placed on white filtering-paper, which was then dried on the waterbath; a brown stain appeared where the liquid had been: this was cut out, and divided into two parts; one of them was moistened with hydrochloric acid, and drops of ferrocyanide and sulphocyanide of potassium placed on opposite sides of the moistened portion; strong iron reactions
were obtained in each case.
The other portion of the stained paper was incinerated and fused on platinum-foil with a little carbonate of soda; with this most delicate test, no trace of the manganese reaction could be observed
It is evident, therefore, that in the case in question the colour of the solution of chloride of lime is due to iron, not to manganese, and it would seem most probable that