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have long notice of the patentee's intention to renew

THE CHEMICAL NEWS. beyond the fourteen years. We almost fear that in these

VOL. XXXIX. No. 1008.

NEW PATENT LEGISLATION.

AMONG the many remedies proposed for the present depressed condition of British manufactures it is more than strange that such an immense majority overlook the simplest means-the encouragement of invention by giving increased facilities for obtaining and retaining patents. When we consider what we owe to invention in the past; when we further reflect that our most formidable manufacturing rivals possess a patent law in most points supe. rior to our own, and that they ascribe to this patent law a very great share in their rapidly-growing industrial prosperity; when we reflect on these things, it does indeed seem to us surprising that patent law reform is not recognised as the question of the day. Our present patent system, though possessing certain meritorious points, labours under very serious drawbacks. Its capital defect is the exorbitant cost of obtaining and upholding a patent, which amounts to £175 in stamp duties alone. It is very true that of this sum £50 are payable before the end of the third and £100 before the expiration of the seventh year respectively. But this plan of periodical taxes, non-payment of which at once renders the patent void, is fatal to the most essential element in the value of every kind of property, viz., security. It is not to be expected that manufacturers will pay a royalty to work a patent which if they only wait for a year may perhaps be thrown open to the world.

If we turn to the United States we find that there one payment of 35 dollars secures to an inventor the absolute right to his ideas for a term of seventeen years. Can we wonder if under such a system working men spend their leisure in trying to devise some improvement, some new "notion," of a useful character, and that foreign inventors are rapidly learning to consider America as the most favourable field for the practical development of their

ideas?

Our national apathy on this most important subject is, however, not quite universal. Messrs. Anderson, Mundella, Dalrymple, and Alex. Brown are about to bring in a Bill which, should it become law, will be a very great improve. ment. The duration of patents is proposed to be extended from fourteen years the present limit-to twenty-one. The stamp duties are to be reduced to £85, of which £10 are payable on obtaining the patent, £25 at the end of seven years, and £50 at the end of fourteen years. Patents already in force may be extended to twenty-one years, and shall be exempt from the payments formerly prescribed at the end of the third and of the seventh year, if not already due, and shall be liable merely to the payments prescribed in the new scale. These proposals, if carried out, would be a boon alike to inventors and to the nation at large. There is extension of time, reduction of cost, and though the vicious system of successive duties is not wholly abandoned, yet every patent, not otherwise voidable, is safe for seven years, which will give the patentee some chance at least of getting it adopted in practice.

Unfortunately, in opposition to this wise and moderate Bill, a measure is to be brought in under the auspices of Government which

"keeps the word of promise to our ear
And breaks it to our hope."

The duration of a patent is to be extended to twenty-one years. But this boon is to be purchased at a cost of another £100, payable at the end of the twelfth year for the very suspicious reason alleged in the memorandum of explanations that the "public"-i.e., pirates-"may

words lurks a possibility that the continuance of a patent for the remaining seven years may be opposed. The stamps duties payable on obtaining the patent are, indeed, to be reduced to £12 10s., but with the further duties at the third, seventh, and twelfth year the total cost will be increased to the enormous sum of £262 10s., whilst the opportunities lapsing from non-payment will be increased from two to three. As a still further blow to security of clause:-" A patent shall be liable at any time after the possession we find the following most mischievous end of three years from its date to be revoked on either of the following grounds: (a) That the patentee fails to within the United Kingdom, or to make reasonable efforts use or put in practice the invention to a reasonable extent to secure the use or practice thereof there, proof to the contrary whereof shall lie on him; or (b) that he fails to grant licences to proper persons requesting the same, on

terms which the Lord Chancellor deems reasonable."

When we remind our readers that in the general opinion be brought into operation so early as the third year, except of practical men it is decidedly exceptional for a patent to the inventor happens to be a capitalist, they will agree with us that this clause, if not in intention a cunninglydevised proviso for the confiscation of patent right, will act as such in practice. Men who would otherwise have come to terms with the patentee will, if this clause becomes law, wait till the third year has expired. We admit that a patentee who works his invention in some foreign country and refuses to do so in the United Kingdom might justly be held to have forfeited his rights. But this end could surely be attained without in substance enacting that no poor man shall hold a patent for more

than three years.

To give the introducers their due, the Bill contains a few good features. The time of provisional protection before giving notice to proceed is extended to nine months, and if a stamp duty has not been paid at the proper date from accident or mistake the Lord Chancellor may, on petition, enlarge the time so as not to exceed three months longer. We know instances where patentees for want of this arrangement have been compelled to apply for a Private Act of Parliament a most costly remedy. There are also increased facilities for amendment, disclaimer, &c., even after sealing.

Still, notwithstanding these minor improvements, if we consider that the cost of a patent, instead of being greatly reduced, will be augmented, and its character of permanonly pronounce this measure a step in the wrong direction, ence within the alloted term as greatly decreased, we can which it is the duty of all friends of the industrial progress of the nation to oppose by every means in their power.

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118

Manufacture of Potassium Iodide,

CHEMICAL NEWS, March 21, 1879.

employ its reciprocal, we have the factor o'00000170157, | of high and regular strength is not unattended with and then the formula becomes

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These results prove the metal to be the so-called manganese steel. Certain metallurgists tell us that such a metal resists shocks very well, and that this enormous quantity of manganese added to the metal neutralises the evil effects of phosphorus. But the best thing that can be done is to avoid the use of such cast-metal cured by manganese. Two strips of the same metal when white-hot were welded together, but when it was attempted to bend them the first blow divided the strip into two pieces through the weld. Steel must not contain more than o'3 to 04 per cent of manganese, and a metal containing 1'50 to 2:00 per cent of manganese is in most cases good for nothing. Inferior material, if even cured by manganese, will always give inferior steel. But as certain works prepare such a curious steel, it would be a benefit for the buyers if the manufacturers would supply them with a true analysis of the steel, because otherwise the buyer may get a castmetal which only the manufacturer can call "steel."

nuisance, and the lixiviation of the barium sulphate requires much time. On the other hand, potassium sulphate can be obtained cheaper and purer than the corresponding carbonate, whilst the barium sulphate can be readily utilised for the reproduction of sulphide.

Method No. 2 obviates the necessity for washing a precipitate, and yields at once a very strong solution of potassium iodide; but the preparation of pure caustic potassa, and the concentration and subsequent fusion are circumstantial and tedious. The author therefore prefers the third method, as ferroso-ferric iodide is easily prepared and the carbonate of iron is readily washed.

To obtain cubic crystals of a porcelain-like appearance it is essential in the first method to ensure the complete decomposition of the barium sulphide by the iodine: if alkaline sulphides are mixed with the potassium iodide the crystals are paltry. If the lye contains iron sulphide, which is soluble in hot and concentrated potassium iodide, the crystals take a blue appearance. An excess of iodine dissolves foreign metals present in the barium sulphide, and the crystals may then be discoloured.

In the case of the second method, irregularity in melting may produce iodic acid, and a caustic potassa not free from sulphates causes the presence in the lye of alkaline sulphide. Both these injurious impurities must be removed prior to crystallising.

In the third method these annoyances are excluded. Salts of sodium must in all cases be avoided. Some manufacturers, to avoid the presence of sulphides, leave purposely a trace of iodate in the lye. The result is that the crystals turn yellow. The presence of lead in the iodine is exceedingly objectionable. This metal is soluble in concentrated potassium iodate, and cannot be precipitated by sulphuretted hydrogen except after great dilution. If not removed lead affects not merely the colour but the forms of the crystals.

No demonstrable trace of potassium carbonate is admissible either for medical or photographic purposes. Potassium iodide, therefore, should be unaffected by salts of barium. The perfect absence of chlorine can never be attained, as even the best sample of iodine as well as of potassium carbonate contain traces of this impurity.

The Chilian iodine, obtained from soda-saltpetre, is becoming a formidable rival to the European product, which ave lost their market for potassium chloride in consecannot be offered at a reduced figure as the manufacturers quence of the rivalry of the Stassfurt mines. Chilian iodine is met with in commerce either as a paste or as copper iodide.-Chemische Industrie.

CHEMICAL CALCULATIONS.

WE have received from Mr. Lupton, Professor of Chemistry at Harrow, a card destined to assist beginners in

THE MANUFACTURE OF POTASSIUM IODIDE. the solution of "chemical problems." By this expression

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the authors means, of course, not the many unsolved questions in chemical science with which so many highly disciplined minds are now grappling, but the problems which are given to pupils as means of instruction, and which, according to Mr. Lupton, "now form a large part of the chemical training at many schools." The card seems to us useful and well arranged for this purpose. It comprises a table of forty-one of the more abundant elementary bodies with their atomic weights and the corresponding logarithms. There is also a table of constants, chemical and physical, with their logarithms.

Whilst we have great pleasure in acknowledging the value of these tables, we cannot help considering it a misfortune that chemistry should be taught merely from books and calculations. We do not deny that the student may thus acquire an extensive and a fairly accurate knowledge of chemical facts and of chemical laws. But the

main educational value of chemistry, and, in like manner, | of physics and biology, as it seems to us, lies hereinthat these sciences, practically taught, train the mind and the outward senses to deal with objects, natural or artificial, and to draw conclusions from facts observed. They thus supply a grievous want in the ordinary system of English public school education where the intellect has been, till lately, solely engaged with words and with abstractions.

ON INDIGO-BLUE

FROM

POLYGONUM TINCTORIUM AND OTHER
PLANTS.

By EDWARD SCHUNCK, Ph.D., F.R.S.

duct of decomposition of the indican of the extract. The latter supposition is the most probable one; for tyrosine being almost insoluble in alcohol could hardly be contained in any appreciable quantity in the alcoholic extract of the leaves.

Some connection between tyrosine and indigo-blue has frequently been suspected by chemists. Indeed a glance at the formulæ of the two bodies will show that some connection is possible, since, by replacing H by CH3 in indigoblue and adding 2H2O, we arrived at the formula of tyrosine, thus:

C8H5NO+CH2+2H2O=C9H11NO3°

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In order to explain the formation of tyrosine from indican we may suppose the latter to split up into tyrosine, indiglucine, acetic acid, and carbonate dioxide, thus:C26H33 NO18+3H2O=C9H11NO3+2(C6H10O6)+ Tyrosine. Indiglucine. +2(C2H4O2)+CO2.

Indican.

Polygonum tinctorium.

SOME papers read before the Society many years ago, and subsequently published in its "Memoirs," contain an account of my experiments with the leaves of the Isatis tinctoria, or common woad, the well-known plant employed in Europe for dyeing blue before the introduc-formed from indican, the question suggests itself whether Supposing the tyrosine in this case to have been really tion of indigo from the East. I showed that the leaves the leucine and tyrosine so frequently found in the animal of this plant do not, as some have supposed, contain either indigo-blue or its hydride ready formed, but yield organism as products of disease, may not be derived from by careful treatment a peculiar glucoside-indican-which, some substance similar to indican rather than directly and when acted on by acids and other reagents, splits up into immediately from albuminoids. indigo-blue and indigo-glucine, the latter being a body resembling glucose. My experiments also show that this substance, indican, is a highly unstable body, undergoing when its watery solution is heated for some time, or, more rapidly, by the action of caustic alkalies, an entire change, on the completion of which it no longer yields indigo-blue by decomposition with acids, but in place of the latter gives indigo-red, indifulvine, leucine, and other products. Though I succeeded in ascertaining the composition of indican and the relation in which it stands to indigo-blue, the difficulty of obtaining large quantities of it in conseqence of its excessive liability to change, prevented my proceeding further with the investigation. It seemed to me, however, that it might be of some interest to ascertain whether other indigo-yielding plants contain ready-formed indigo-blue (as has been maintained with so much persistence), or whether the colouring-matter exists in the vegetable cells in the form of indican or some other glucoside; and I have accordingly examined such of the plants known to give indigo as I have been able to procure.

Before stating the results to which I wish to direct attention on this occasion, I may mention an observation belonging, strictly speaking, to the part of the subject previously treated of, which, however, I will now describe in a few words, as I may not have another ooportunity of doing so. In my last memoir I stated that, among the products of decomposition of indican from Isatis tinctoria, leucine is usually found, sometimes, indeed, in considerable quantities. In some more recent experiments made with woad leaves I obtained, besides leucine, a substance having all the properties of tyrosine. This substance was only slightly soluble in cold water, but soluble in boiling water, from which it separated on cooling in long needles, forming, when dry, a snow-white felted mass. Its watery solution gave the well-known reaction with mercuric nitrate. Its solution in concentrated sulphuric acid, after neutralisation with barium carbonate, gave a purple colour with ferric chloride. According to Prof. Gamgee, who had the kindness to examine the substance for me, it showed under the microscope the forms characteristic of ordinary tyrosine. There could be no doubt therefore, of its identity with the latter. As the tyrosine in this case was not obtained from pure indican, but from the crude alcoholic extract of the leaves, it is impossible to say whether it pre-existed in the plant or whether it was a pro

Memoirs," ser. 2, vol. xii.,p. 177, and vol. xiv.,
p. 181.

This plant has long been known and employed as a gource of indigo by the Chinese. According to Stanislas Julien, who has given translations from Chinese works of various process for extracting indigo from the leaves, the plant is called in China Lân, the most productive variety being termed Tcha-Lân, i.e. the Lân resembling the tea shrub. It was introduced into Europe in the eighteenth century, and at one time, particularly about the years 1838 to 1849, formed the subject of numerous investigations by eminent French botanists and chemists, such as Turpin, Joly, Baudrimont, Pelletier, Robiquet, and others, some hopes being entertained that the plant might be cultivated profitably in France. The numerous trials made with this view having led to no result, the matter fell again into oblivion, and this interesting plant remained what it was before, a mere curiosity.

I obtained the seeds of the plants from Messrs. Vilmorin, Andrieux, and Co., the eminent horticulturists of Paris, and therefore felt sure of their genuineness. They were sown in a hotbed, and germinated rapidly. As soon as the young plants were a few inches high they were transplanted into the open ground, where they grew vigorously, producing an abundance of leaves and attaining during the summer season a height of nearly three feet. Towards the end of summer spikes of pretty pink flowers, resembling those of other species of Polygonum, made their appearance. The seed, however, did not ripen in the open air, the plant being cut down by the early frosts before this could take place; but, by growing a few plants under glass, I obtained a quantity of well-matured seeds, which yielded another crop in the following season.

For a botanical description of Polygonum tinctorium I must refer to Turpint and Joly, the latter of whom has given a full account of its structure and affinities. Of the various organs, the leaves, being the seat of the blue colouring-matter, are alone of any interest to the chemist. These leaves, which are large, oval in shape, and glossy, show no indication of the presence within their tissue of any pigment besides the chlorophyll to which they owe their lively green colour, except, occasionally, in certain places where they have suffered injury from the bites of

*Comptes Rendus, t. vii., p. 703.

+ Comptes Rendus, t. vi, p. 806.

1 "Sur le Polygonum tinctorium: Montpellier, 1839.

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insects or from others causes, and where blue spots make | their appearance-a phenomenon which I shall endeavour to explain presently. It is nevertheless easy to show that they contain a considerable quantity of what the French call a matière colorable, i.e., a substance which, though colourless in itself, yields colouring-matter by appropriate treatment. A few leaves having been cut into pieces and rubbed up with a little water in a mortar to a thin paste, the mass is poured on a bit of calico, and yields, by squeezing and kneading, a green muddy liquid which, on the addition of a little sugar of lead solution, gives a green flocculent precipitate containing the chlorophyll, albumen, and other matters previously held in suspension. The liquid filtered from this precipitate is clear and yellow, and on being mixed with sulphuric or hydrochloric acid and left to stand for several hours, yields a deposit consisting of tolerably pure indigo-blue. The amount of colouring-matter obtained in this way from Polygonum tinctorium is far greater than that which the same quantity of woad-leaves grown in the same locality would produce, proving that the yield is influenced not only by soil and climate, but also by the peculiar nature of the plant. The isolation of the matière colorable of Polygonum tinctorium is still not a very easy task. The same precautions must be observed as in the case of Isatis tinctoria, particularly as regards the evaporation of the solvents employed, which must always be effected without applying artificial heat. Unless some means are at disposal for evaporating rapidly at the ordinary temperature, by means of a current of air or otherwise, success is very uncertain. The method formerly employed in preparing indican from Isatis tinctoria was first tried. The leaves of the plant were dried in a stove moderately heated, and, while still warm, ground to powder. The powder, which had the colour of fresh hay, was passed through a hair sieve to separate the leaf-stalks and other fibrous portions, and then extracted in a percolator with spirit of wine. The green alcoholic extract was evaporated in a shallow tin dish, the evaporation being assisted by passing a current of air over the surface of the liquid in the apparatus formerly described. Chlorophyll and fatty matter were deposited during evaporation, leaving a brown watery liquid, which was poured off, agitated with freshly precipitated copper oxide, and filtered. The copper in the filtrate was precipitated with sulphuretted hydrogen, and the filtered liquid was evaporated as before. The residue was treated with absolute ether, which dissolved a portion, and left, on evaporation, a yellow syrup. This syrup is the indigo-producing body as pure as it is possible to obtain it. I prefer to this the following process, as being more expeditious and surer. The alcoholic extract of the dried leaves having been evaporated, the watery liquid which is left is mixed with acetate of lead solution, which gives a dirty yellow precipitate, consisting of chlorophyll and other impurities in combination with lead. To the clear yellow filtrate basic lead acetate is added; this gives a primrose-yellow precipitate, which is filtered off and, after being washed with water and then with alcohol, is suspended in absolute alcohol, through which a current of carbonic anhydride is passed. After the gas has passed through for some time the liquid acquires a yellow colour, and, after being filtered from the insoluble portion, consisting principally of lead carbonate, is evaporated at the ordinary temperature. Water added to the residue leaves a portion undissolved, which is filtered off. Sulphuretted hydrogen is passed through the filtrate to precipitate the lead contained in it; and having been again filtered, it is evaporated, when it leaves a syrupy residue which may be treated with ether as before.

CHEMICAL NEWS, March 21, 1897.

colour on the addition of caustic alkali, and gives with basic lead acetate a light yellow precipitate. When the watery solution is mixed with a little sulphuric or hydrochloric acid and left to stand for some time, the surface of the liquid becomes covered with a film of indigo-blue, a deposit of the same substance being usually formed at the bottom. The filtered liquid shows, when tested with a salt of copper and an excess of caustic alkali, the wellknown reaction of glucose. If, however, the watery solution is left to stand at the ordinary temperature for a considerable time, or if it is simply boiled for some time, or if it is mixed with caustic alkali and left for a short time, it no longer yields indigo-blue on the addition of acid. This is probably due, as I have shown to be the case with indican, to a molecular change, resulting, when completed, in the formation of a body which, when decomposed with acids, yields indirubine and brown resinous substances in place of indigo-blue. When a large quantity of watery solution is mixed with acid and left to stand, a portion of the substances undergoes, it seems, the same change; for the deposit formed when operating with one litre or more of the solution contains not only indigo-blue, but also indirubine, indifulvine, and other products. The deposit, which in this case is almost black, after being filtered off, washed, and dried, is treated first with caustic alkali and then with cold alcohol, in order to remove the indifulvine and other resinous substances. On treating the residue with boiling alcohol, the indirubine dissolves, and is obtained, after several crystallisations, in the beautiful dark-red needles characteristic of the substance. The portion insoluble in boiling alcohol is indigo-blue, requiring for its purification merely to be disssolved in some suitable menstruum, such as boiling aniline. I am inclined to think that the same molecular change takes place in the cells of the plant during the later stages of its development; for I obtained from some leaves gathered late in the season when the flowers had begun to appear, a quantity of indican having the usual appearance, but giving, by decomposition with acid, far less indigo-blue and more indirubine and other products than the indican from younger leaves. This result was confimed by experiments, to be described presently, made with the leaves themselves. (To be continued.)

NOTICES OF BOOKS.

A Practical Treatise on the Manufacture of Sulphuric Acid. By A. G. Lock and C. G. Lock. London: Sampson Low, Marston, Searle, and Rivington. WE have here a thoroughgoing and a practical book on what may fairly be pronounced the most important branch of industrial chemistry. The authors, unlike too many compilers of so-called technological works, do not content themselves with generalities, but enter closely into working details. The construction of the kilns and chambers, with their accessory arrangements, the selection of materials, the points needful for economy in management, and the prevention of waste and nuisance, are all carefully and clearly presented to the reader, with the important aid of seventy-seven "construction plates" drawn to scale and showing the chief recent improvements.

It may seem strange, if not somewhat humiliating, that in a manufacture so old and so widespread as that of sulphuric acid, and depending so little on manipulative niceties, there should be so much divergence of opinion concerning arrangements of plant and methods of working. Still, from another point of view, it may be held consolatory to know that one, and that not the smallest, of our national industries is capable of very decided improvements if those who combine the opportunity and the requisite knowledge will give the question the careful examination it deserves.

The indigo-producing body thus obtained is, if it be permitted to draw a certain conclusion from mere qualitative reactions, identical with the indican of Isatis tinctoria. Its appearance is that of a yellow transparent syrup, showing no tendency to assume a crystalline form. It is soluble in water, alcohol, and ether. The watery solution has a more or less acid reaction. It becomes of a deep yellow. Our authors begin with a consideration of the raw

material, a subject which derives additional importance from the growing objection to the industrial uses of arsenical products, and from arsenic no pyrites are absolutely free. It remains to be seen whether the vast deposits of sulphur in Iceland may not enable us to overcome this difficulty, situate as they are so much nearer our shores than are the Sicilian mines. We notice that Messrs. Lock quote from Mr. H. A. Smith the statement that in certain Irish pyrites the arsenic present exceeds 2 per cent. They are also, on an average, low in sulphur, and are very hard, if not altogether impossible, to burn reasonably clean—a fact which goes far to vitiate the details of production-cost quoted from Messrs. Richardson | and Watts as to the relative economy of brimstone, of Belgian, and of Irish pyrites. In a subsequent part of the work the authors express a preference for the best-class Norwegian pyrites beyond all others.

The observations on the analysis of sulphur ores are too brief to be of much practical value, and might have been advantageously omitted, especially as this subject is discussed at length in other works.

The structure of kilns for brimstone and for different qualities of pyrites is treated very fully, with the aid of plates representing the special arrangements for a rich Norwegian ore, for a poor Irish, and for the poor English sulphur ores from the coal-fields, commonly known as "coal-brasses" or brass lumps. There are, besides, representations of the kiln fronts of Messrs. Daglish and •Co., and of Gerstenhofer's kiln, now very extensively, and we believe successfully, used on the Continent.

The capacity, shape, and arrangement of chambers are considered in the second chapter. Here, it must be owned, practical men are very far from having come to a unanimous conclusion as to the best construction-an evident proof that we have here much still to learn. The authors quote with disapprobation, or at least with strong doubt, the dimensions recommended by Mr. H. A. Smith, viz.-" Length, 160, 200, or even 210 feet; width, 30 feet, increasing in ratio to length; and height, 10 feet, not to be increased for any length of chamber." As grounds for rejecting these proportions they allege the great consumption of lead in proportion to bulk, and they show that a chamber 210 feet by 30 feet, having only 1 inch of acid all over the bottom-the very smallest depth needful to prevent the escape of the gases-will lock up 23 tons of acid. As the opposite extreme they mention Hasenclever's proportions, where the minimum height of the chambers is fixed at 32 feet to 130 feet in length and 32 feet in breadth. It surely ought to be possible to decide which of these two glaringly opposed systems gives in practice the best results, and whether either of them is preferable to the less extreme dimensions recommended by the authors, viz. In a set of 60 feet long, 27 wide, and 23 feet high, and 30 feet long, 23 feet wide, and 22 feet high.

The proposal to inject "atomised " or pulverised water into the chambers in place of steam is next passed under review, as also the suggestion to admit a solution of nitre in the form of spray. But on these questions the anthors, though citing the opinions of others, do not appear to have formed any decided conclusion of their own.

The evidence adduced on the proposal to use free nitric acid instead of nitrate of soda seems decidedly favourable to this system, which is almost universally adopted on the Continent. In some German works the consumption of nitre in this form has been brought as low as 1, 1, and even, it is said, I per cent of the sulphur present in the pyrites. The nature of this economy will be fully appreciated if we remember that where no Gay-Lussac's or Glover's tower is in use some manufacturers use 9 or even 10 lbs. of nitre to every 100 lbs. of sulphur actually burnt, and that even where such contrivances are at work the proportion often reaches 5 per cent. Dr. Lunge, whom we consider an excellent authority, considers the free acid so much superior to the nitre that nothing but a fear of having too much difficulty with the workmen in the first instance would deter him from discarding the latter system in England.

This last remark suggests some unpleasant reflections. One of the many reasons which place us at a disadvantage in competing with foreigners is the obstinacy with which the British workman clings to traditional methods, and his disinclination to give fair play to any new invention which he may be called upon to adopt.

The chapter on "chamber construction" is admirably complete and practical.

In treating of "condensers and columns" the evidence for and against the use of the Glover tower is fairly stated. The authors consider it certain that in large works, at least, this tower will become as common an adjunct as the Gay-Lussac column.

The succeeding chapters on the concentration of the acid, on the utilisation of waste products, and on accessories must be pronounced satisfactory, though we regret that want of space forbids us to examine them in detail. The final sections on attempts to manufacture sulphuric acid without the use of chambers, and on the so-called Nordhausen or fuming acid, will also be found valuable and suggestive. The latter acid is now in extensive demand in the arts, e.g., in preparing the sulpho-conjugated acids of certain coal-tar colours, and in the purification of ozokerite. As shippers and railway companies dislike undertaking its conveyance there is the greater need for its production on the spot.

In concluding this necessarily brief sketch, we beg to record our opinion that though no reading will enable a man to dispense with actual experience, yet that the authors have done all that can be done in the form of a book. Every chemical manufacturer, every scientific chemist who is at all connected with practical operations, has room for gratitude to the authors.

The book is admirably got up, and reflects great credit on the publishers.

Our Domestic Poisons, or the Poisonous Effects of Certain Dyes and Colours Used in Domestic Fabrics. By H. CARR, M.Inst.C.E. London: Ridgway.

ARSENIC is in more senses than one a delicate thing to handle. On a somewhat similar occasion we ventured to put to the accuser a few questions, such as would have been urged by counsel if the matter had come before a court of law, and in consequence we were half buried beneath a heap of indignant letters. In the present pamphlet it is maintained that "national health is suffering from the use of arsenic and other poisons in the manufacture of domestic fabrics," and the author takes in hand to arouse public feeling with the end of demanding legislative interference. For this purpose he has put himself in communication with certain eminent physicians and chemists, and has obtained from them evidence more or less confirmatory. The first point which here strikes us is that Mr. Carr has not-as far as here appears-applied to any chemist specially and practically acquainted with the arts of dyeing and calico-printing and able to inform him what poisonous colours are actually in use and what are the circumstances of their application. The instances of poisoning given, at least, as far as textile fabrics are concerned, are by no means as explicit as could be wished. We seek to know in such cases the name and address of patient, medical adviser, and chemist, if one has been called in; the date of the occurrence, and the precise name of the colour said to have occasioned the mischief. The terms "mauve-dyed articles," "beautiful red, scarlet, and mauve colours," &c., are too vague to be employed in so serious a question. These demands may perhaps seem stringent, but it would be difficult to name any subject which has given rise to so many newspaper canards as the alleged poisonous character of dyes. Our contemporary, Dr. Reimann, of the Färber Zeitung, has been at the pains of sifting not a few of these stories. In many cases it was found on rigid scrutiny that the alleged sufferer and his doctor were both non-existent. At other times the source of the disease has been declared to be

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