Obrazy na stronie

Nov. 24, 1876.
} Chemical Notices from Foreign Sources.

227 Before writing this I have taken great pains to under-, ment. It is very adhesive ; though mat, it is capable of stand Major Ross's paper, and I could almost say that I taking a fine polish, and may be introduced in the decorado so were it not for the sentence which occurs at the end of tion of objects of art. Antimony can be deposited from a his fifth paragraph. But here I frankly admit I have solution of the double chloride of antimony and ammonium failed. After experimenting upon all the known relations at common temperatures. It frequently serves to replace of “that that " to "this," and of “that this" to " that" platinum-black in a number of fine art manufactures. by analysis and synthesis (and, I had almost said, the Deposits of palladium are obtained with ease by means " sodium hypothesis "), I have been obliged to abandon of the double chloride of palladium and ammonium, either the problem.--I am, &c.,

with or without the battery. The solution must be perNaHO. fectly neutral.

New Dynamo-Magnetic Phenomenon.-MM. Trève ON ANTHRACENE TESTING.

and Durassier.-Let there be a horse-shoe magnet, of any length, covered upon one side with varnish, or, better,

with a plate of glass. If there is laid upon the neutral To the Editor of the Chemical News.

part a cylinder of soft iron, it is seen to move towards the Sir,-Mr. Caspers' remarks on my investigation on poles, which it reaches in a time which is a function of anthracene testing require my immediate reply.

the weight of the cylinder and of the coercitive force of Mr. Caspers is guilty of a singular want of tact, by first the magnet. Hence there results a new method of estiobtaining from me private information, and an exceptional mating the magnetic force by the mechanical work which sample of anthracene, and then utilising the same in con- it effects. tradicting my statements, withour informing me of his in

Detection of Magenta in Wine.-M. E. Bouilhon.tention to do so. Such conduct is happily unknown in Five hundred c.c. of wine are placed in a capsule, raised the scientific world, or there would soon be an end of all

to a boil, and evaporated down to 125 c.c.; the capsule is free exchange of ideas on scientific matters. But Mr. then withdrawn from the fire, and 20 grms. crystalline Caspers is no chemist, and I cannot discuss with him hydrate of baryta are added. It is agitated to facilitate theoretical questions: his observations on my results are the reaction, allowed to cool, poured upon a filter, and valueless. Mr. Caspers, with charming simplicity, shows his in all 125 c.c. of filtrate. It is then necessary to ascertain,

the precipitate washed with distilled water, so as to obtain ignorance of the first rudiments of chemistry when he by the addition of a few crystals of hydrate of baryta to says—"Nearly all coal-tar distillers, even those who work the filtered liquid, that the precipitation of the colouring under the direction of efficient chemists, have unpersuadedly matter of the wine is complete: if not, more hydrate of to believe that the specific gravities of quinone and anthra- baryta must be added, and the liquid re-filtered. It is then cene are in proportion like 1000 : 856."

introduced into a flask containing about 250 c.c., with 50 Apart from the mass of confused ideas compressed into to 60 с.c. of pure ether, strongly shaken, and allowed to a few lines, the fact clearly stands out that the writer does seuile. When the ether is completely separated from the not know the difference between specific gravity and aqueous liquids it is drawn off by means of a pipette, and atomic weight, and I must simply decline to notice any poured into a porcelain capsule. A drop of acetic acid at future criticisms coming from such doubtful authority. 18° is added, 3 or 4 drops of distilled water, and a little I am, &c.,

white unwoven silk, consisting of ten threads a centimetre FredeRICK VERSMANN.

in length. If the quantity of magenta contained in the 35, Whitecross Place, Wilson Street,

wine is at all notable acetic acid produces at once a rose Finsbury, E.C.

colouration, but when only minute traces are present the ether is allowed entirely to evaporate. The residue con

sists of a small quantity of aqueous liquid, in which the CHEMICAL NOTICES FROM FOREIGN to evaporate the bulk of this liquid, and concentrate the

silk soaks. The capsule is then very gently heated, so as SOURCES.

traces of colouring matter in a few drops, thus favouring its fixation upon the silk. This process, if carefully

executed, reveals one hundred-millionth part of magenta Note.-All degrees of temperature are Centigrade, unless otherwise in wine.

expressed. Comptes Rendus Hebdomadaires des Seances, de l'Acadenie

Reimann's Farber Zeitung. des Sciences. No. 19, November 6, 1876.

No. 39, 1876. Researches on the Production of Electro-Chemical

Pittakall is manufactured by a company in Hanover Deposits of Aluminium, Magnesium, Cadmium, Bis- under the name of violacein. muth, Antimony, and Palladium.-M. A. Bertrand.

The use of vanadic aniline-blacks is greatly on the inThe author has obtained deposits of aluminium on decom.

crease in France. The colour obtained is fast, both as posing with a strong battery a solution of the double against milling and acids. chloride of aluminium and ammonium. A plate of copper,

Mahogany is again recommended as a dye-ware. The forming the negative pole, whitens gradually, and becomes shades obtained are reported to resemble the colour of the covered with a layer of aluminium,

which takes a brilliant wood itself, and to be very fast. The mordants used are polish under the burnisher. The double chloride of mag

acetate of alumina for cotton, and sulphates of iron and nesium and ammonium in an aqueous solution is readily copper for wool. decomposed by the battery, giving in a few minutes strongly adherent and homogeneous deposits of magnesium upon a sheet of copper. It polishes readily. The battery

MISCELLANEOUS. must be powerful. Cadmium is best deposited from the bromide to which a little sulphuric acid has been added. It is then very coherent and very white, and takes a fine Organisation Among Chemists.-The adjourned polish. The sulphate, if acidulated, also gives an imme- meeting to discuss this subject assembled in the Chemical diate deposit of metallic cadmium, very adhesive, and Society's Room, Burlington House, on Saturday, capable of a fine polish. Bismuth is deposited from a November 4th, 1876. Prof. F. A. Abel, F.R.S., President solution of the double chloride of bismuth and ammonium of the Chemical Society, in the Chair. The minutes of upon copper or brass by the current from a Bunsen ele- the previous meeting were read and confirmed. The


Prof. Abedio Manel Allen (Sheffield); P. H. Lewahim A COURSE of QUALITATIVE CHEMICAL


Organisation among Chemists.

{ ,

Nov. 24, 1876. Report of the Committee appointed to confer with the

Council of the Chemical Society was read. It was pro-
posed by Mr. J. A. Wanklyn and seconded by Prof. MONDAY, 27th.-Royal Geographical, 8.30.
Redwood :-"That the cordial thanks of the meeting be

Medical, 8. tendered to the President and Council of the Chemical Tuesday, 28th.--Civil Engineers, 8.

Society of Arts, 8. Cantor Lectures. Society for the consideration given by them to the pro

Anthropological Institute, 8. posals of the Organisation Committee, and for the efforts

Manchester Literary and Philosophlcal Society, 7. made by them to meet the views of the Committee in

WEDNESDAY, 29th.-Society of Arts, 8.

THURSDAY, 30th.- Royal, 4. (Anniversary.) relation to these proposals." (Carried unanimously.). It Friday, Dec. ist.-Geologist's Association, 8. was proposed by Prof. Frankland, F.R.S., seconded by SATURDAY, Dec. 2nd.-Physical, 3. “On some Mechanical IllustraDr. Voelcker, F.R.S., and supported by Dr. Williamson,

tions of Thermo-Electric Phenomena," by

0. J. Lodge, B.Sc. F.R.S.:-—"That, having regard to the limited powers of the Chemical Society under its charter, it is desirable that an Association be formed that shall be independent of

TO CORRESPONDENTS. the Chemical Society, and that the Organisation Com

5.7.L.-We should think there is alum in the paste. mittee already formed be dissolved, and that the following G.M.—The part of the Report to which you reser has not yet apgentlemen, or such of them as may be willing to act, form peared in our columns. a new Committee (with liberty to add to their number)

R.L.-Dr. Versmann's letter renders the publication of your's unto settle the form and details of the scheme, and to take

ERRATUM.–Page 212, col. 1, line 3 from top for "250° C.” read all steps necessary to secure the formation and incorpora. 275 C." tion of the proposed new Association." (Carried unanimously.) The proposed Committee are the following:- Now ready, Fourth Edition, with Engravings, 8vo., 7s. 6d., ; Prof. Attfield; Mr. I. Lowthian

ANALYSIS. By William G. VALENTIN, F.C.S., Principal Bell (Middlesbrough); Prof. Bloxam ; Prof. Crum Brown Demonstrator of Practical Chemistry in the Royal School of Mines (Edinburgh); Mr. M. Carteighe; Mr. Dugald Campbell ; and Science Training Schools, South Kensington. Mr. W. Crookes ; Mr. G. E. Davis (Runcorn); Dr. Dupré;

J. and A. CHURCHILL, New Burlington Street. Prof. James Dewar (Cambridge); Mr. F. Field; Mr. R. J. IMPORTANT WORK ON DYEING AND Friswell; Prof. Frankland; Prof. Gladstone; Mr. George

CALICO PRINTING. Gore (Birmingham); Prof. Galloway (Dublin); Mr. C. Ē.

Second Edition, in One Large 8vo. Volume of 550 pages, strongly Groves ; Mr. W. N. Hartley ; Mr. C. W. Heaton ; Mr.

bound in cloth, Illustrated with numerous Wood Engravings, Douglas Hermann (St. Helens); Mr. David Howard ;

and 57 Specimens of Printed and Dyed Fabrics, Mr. C. T. Kingzett; Prof. Marréco (Newcastle); Mr. F.

Price 215.

CALICO PRINTING: Neison ; Prof. Odling (Oxford); Mr. F. J. M. Page ; Mr. including an account of the most recent improvements in the J. Pattinson (Newcastle); Dr. B. H. Paul; Mr. W. H. Use and Manufacture of Aniline Colours. Perkin; Mr. C. H. Piesse; Prof. Redwood; Prof. Emer.

By the late son Reynolds (Dublin); Dr. W. J. Russell; Dr. R. Angus

Dr. F. CRACE-CALVERT, F.R.S., F.C.S. Smith (Manchester); Dr. H. Sprengel; Dr. Stevenson;

Edited by Mr. R. Tatlock (Glasgow); Mr. E T. Teschemacher ;

JOHN STENHOUSE, LL.D., F.R.S., Prof. R. V. Tuson; Dr. Voelcker; Mr. J. A. Wanklyn ;

and Prof. Williamson ; Mr. J. T. Way; Dr. C. R. A. Wright.

CHARLES EDWARD GROVES, F.C.S. A vote of thanks to the Chairman (Prof. Abel) for presiding was carried by acclamation, and a vote of thanks to the Manchester: PALMER & HOWE. London: SIMPKIN & Co. Secretaries terminated the proceedings. The majority of the gentlemen whose names have been proposed have Carbonate of Strontia for Sale.—Apply to

A. Keiffenheim and Co., 27, Side, Newcastle-on-Tyne. agreed to aid in forming the Institution.

REFINED ANTHRACENE New Work by Professor Hayden.-An important

AND OTHER work is now being issued by Prof. F. V. Hayden, whose

COAL-TAR PRODUCTS. name is a sufficient guarantee of its scientific value. The title is “The Yellowstone National Park and the

HENRY SCHOLEFIELD, Mountain Regions of Portions of Nevada, Idaho, Colorado, and Utah," by Prof. F. V. Hayden, Geologist-in-charge of

Cleadon Chemical Works, Newcastle-on-Tyne. the U.S. Government Expeditions to the Yellowstone

COUNTY OF WORCESTER. Valley of the years 1871 and 1872, and of the U.S.

" THE SALE OF FOOD AND DRUGS ACT, 1875." Geological and Geographical Survey of the Territories. The work is illustrated by chromo-lithograghic reproduc- The

'he Justices of the County of Worcester are tions of water-colour sketches taken by Thomas Moran. ledge, skill, and experience," as ANALYST OF ARTICLES OF

desirous to appoint a person, "possessing competent know. The price for the complete work, 5 parts, with text, is FOOD AND DRUGS sold within the County. 50 dollars. The text will be published simultaneously in The duties of such Officer are to analyse any articles of food English, French, and German. The list of plates includes

and drugs which may from time to time be submitted to him by the Hot Springs of Gardiner's River, Yellowstone National Analyses. The person appointed will be required to reside in or near

proper authority, and to furnish Certificates of the result of such Park; The Great Blue Spring of the Lower Geyser Basin, the City of Worcester. He is prohibited by the Statute from being Yellowstone National Park; The Castle Geyser-Upper engaged, directly or indirectly, in any trace or business connected Geyser Basin, Yellowstone National Park ; Lower

with the sale of food or drugs within the County, but may practise as

an analytical and consulting chemist, physician, or surgeon. Yellowstone Range, Yellowstone National Park; Yellow. The salary will be £100 per annum. stone Lake, Yellowstone National Park; Tower Falls Applicants for the appointment are requested to send a statement of and Sulphur Mountain, Yellowstone National Park; Head their qualifications, with original or copy Testimonials, to the underof Yellowstone River, Yellowstone National Park; The signed, on or before the 4th day of December next.

WM. NICHOLS MARCY, Grand Canon, Yellowstone, Yellowstone National Park;

Clerk of the Peace. The Towers of Lower Falls, Yellowstone National Park; County Hall, Worcester, The Mountain of the Holy Cross; The Mosquito Trail,

November 15, 1876. Rocky Mountains of Colorado ; Summit of the Sierra Nevada ; Great Falls of Snake River ; Valley of Babbling the testing required in an Alkali Works. State salary required Waters, Southern Utah ; The Great Salt Lake of Utah. -Address, M. N., Chemical News Office, Boy Court, Ludgate Hill

London, E.C.

Dec. 1, 1876.
Repulsion Resulting from Radiation.


requires some care. It should be drawn from fint glass, THE CHEMICAL NEWS, as this gives much tougher threads than foreign glass.


The diameter varies with the amount of torsion required;

it may be o‘001 inch or less. I select the piece best VOL. XXXIV. No. 888.

adapted for the special experiment in the following way :-Several threads of glass are first drawn out before the blowpipe, and a certain number selected as being

likely to answer the purpose. These are then suspended ON REPULSION. RESULTING FROM

side by side to a horizontal rod and equalised as to RADIATION.-PART II.*

length. A piece of glass rod, about 2 inches long, which

is always kept for this purpose, is then cemented by By WILLIAM CROOKES, F.R.S., &c.

shellac on to the end of one of the threads. Air currents (Continued from p. 220).

are then cut off by a glass screen, and the thread being set in movement by a slight twist, the torsion is measured

by timing the oscillations. This having been done with 101. The difficulty which attended experiments with the each thread in succession, one is selected and mounted balances and bulb apparatus used at first was to bring the in the apparatus. If it works properly, well and good; moving part accurately back to zero, and also to measure if not, it is easy to select a thread having the requisite the deflection produced. I therefore tried several plans of amount of torsion, more or less, and substitute it for the giving a fixed zero-direction to the movable index. Thus one first used. å piece of magnetic oxide of iron was cemented to one

FIG. 6. end of the index, and a permanent magnet was brought Dear it. This answered pretty well, but was inconvenient,

f besides not being sufficiently accurate. A bifilar suspen. sion from cocoon-fibres seemed likely to succeed better; but the difficulty of suspending the rod in this manner, so as to get exa&ly the same tension on each fibre, was very great, and unless this was done there was more tendency

9 to move in one direction than in the other. When I had succeeded in suspending the needle with an equal tension on each silk fibre, I found their elasticity to vary; and as soon as the vacuum was approached one was sure to contract more than the other, twisting the needle out of the axis of the tube, and sometimes causing it to touch the side. This method of suspension was therefore abandoned.

By increasing the length of the needle, and also of the fibre used to suspend it, it was possible to employ fibres with a considerable amount of torsion, and still preserve the delicacy of the apparatus. Fine platinum wire was first tried; but this was soon abandoned in favour of glass fibres, which were found to answer so perfectly that I have since used nothing else.

102. Fig. 7 shows the form of apparatus which I have finally adopted, as combining the greatest delicacy with facility of obtaining accurate observations, and therefore of getting quantitative as well as qualitative results. It

d' is a torsion apparatus in which the beam moves in a horizontal plane, and may be called a horizontal torsion balance. a b is a piece of thin glass tubing, sealed off at the end b and ground perfectly flat at the end a. In the centre a circular hole, c, is blown, and another one,


Tz c', at the end; the edges of these holes are ground quite fiat. a, c, and c' can therefore be sealed up by cementing flat transparent pieces of plate glass, quartz, or rock-salt,

In fitting up one of these apparatus threads were drawn a, d, and d' on to them (83). To the centre of a b an

out which were found to require, respectively :upright tube, e f, is sealed, having an arm, g, blown on

44 seconds, to it for the purpose of attaching the apparatus to the

30 pump.

28 hi is a glass index, drawn from circular or square (22) glass tube, and as light as possible consistent with the needful strength. A long piece of this tube is and

31 first drawn out before the blowpipe ; and it is then for a half oscillation when the glass weight was hung on to calibrated with mercury until a piece is found having their ends. The one oscillating in 30 seconds was first the same bore throughout: the necessary length is then used, but was found to give insufficient torsion. The one cut from this portion. j k is a very fine glass fibre, making half an oscillation in 11 seconds was then used, cemented at j to a piece of glass rod, and terminating at and was found to answer well. Before I adopted this k with a stirrup, cut from aluminium foil, in which the plan days were frequently wasted in the attempt to hit glass index, h i, rests. In front of the stirrup is a thin upon a glass thread of the requisite degree of fineness. glass mirror, shown at k, silvered by Liebig's process, and 104. In taking accurate observations with an apparatus either plane or concave as most convenient. At the ends of this description, it is necessary to support it on a of the glass index (h i) may be cemented any substance stand firmly fastened to a main wall. When resting on with which it is desired to experiment; for general ob. a bench, or connected in any other way to the floor, there servations I prefer to have these extremities of pith, as is a constant oscillation which keeps the index from zero. thin as possible, and exposing a surface of 10 millimetres The apparatus being fastened firmly to its stand, acsquare. The pith may be coated with lampblack or curately levelled, and sealed on to the pump, a divided silver, or may retain its natural surface.

scale, á b (fig. 8), is placed four feet from the small mirror; 103. The preparation of the suspending thread of glass' and immediately beneath the scale is a narrow brass slit,

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CHEMICAL News, 230 New Process for Titrating A stringent Substances. {

Dec. 1, 1876. c, illuminated by a lamp, d. In front is a lens, e, which for some weeks, as the residual moisture in the pith w throws the image of the slit on to the mirror, where it is then have been absorbed by the sulphuric acid in the reflected back again on to the divided scale. Here the pump. angular movement of the bright line of light shows the

(To be continued.)

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minutest attractive or repulsive force acting on the pith

NEW PROCESS FOR TITRATING at the extremity of the movable index.

ASTRINGENT SUBSTANCES. In order to keep the luminous index accurately at zero,

By M. FERDINAND JEAN. except when experiments are being tried, extreme precautions must be taken to keep all extraneous radiation from ađing on the apparatus. A slightly conical paper tube, When we pour drop by drop a solution of iodine into any f, about 6 inches long, and as parrow as the angular decoction of an astringent matter, previously mixed with movement of the ray of light will admit of, is cemented an alkaline carbonate, we remark that this solution is on to the glass window in front of the mirror; and a absorbed with a great energy. I have observed that the similar tube, g, is cemented on to the quartz window in absorption of the iodine takes place, in these conditions, front of the pith surface on which radiation is to act. in the direct ratio of the quantity of astringent matter The latter tube is furnished with card shutters, h, i, at taken, and that i part by weight of tannic acid absorbs each end, capable of easy movement up and down. The 4 parts of iodine before we can observe the presence of whole apparatus is then closely packed on all sides with free iodine in the liquid. It is on this action of iodine on a layer of cotton-wool, about 6 inches thick, and outside astringent matters that the process of titration is based this is arranged a double row of Winchester quart bottles, which forms the subject of this note. The solution of j, j, filled with water and covered with brown paper, iodine necessary for titrating tannin is obtained by disspaces being only left in front of the paper tubes. ķ and solving in iodide of potassium 4 grms. of iodine, and i represent the positions of the candle 140 and 280 adding to the solution distilled water in quantity suffici. millims. distant from the pith. The whole arrangementent to make a volume of 1000 c.c. To ascertain the has the appearance shown in fig. 8.

value of the solution of iodine, we introduce into a beaker 105. I will not discuss at present the phenomena pre- 10 C.C. of a solution of tannin at o'i grm. per cent; we sented when the apparatus is full of air, or when the mix it with 2 c.c. of an alkaline lye containing 25 per cent vacuum is imperfect, but will proceed to the effects ob- of crystallised carbonate of soda; then, by the aid of a served when the exhaustion has been pushed to the graduated burette, we cause to fall into the alkaline liquid highest attainable degree. However much the results the solution of iodine until a drop of the mixture, taken may vary when the vacuum is imperfect, or when the with the glass stirrer and put on a leaf of starched paper, apparatus is full of air, I always find them agree amongst produces a light violet spot, which indicates the presence themselves when the residual gas is reduced to the of free iodine and the end of the operation. The value minimum possible; and I have also ascertained that it thus obtained must be corrected, that is to say we must is of no consequence what this residual gas is. Thus 1 deduct from the number of cubic centimetres of the soluhave started with the apparatus filled with various tion of iodine corresponding to o‘or grm. of tannin, the vapours and gases, such as air, carbonic acid, water, volume of this solution, which it is necessary to employ iodine, hydrogen, or ammonia; and at the highest rare- as pure loss before obtaining a coloured reaction on faction i'find no difference in the results which can be starched paper. For this purpose we measure 10 c.c. of traced to the residual vapour, assuming any to be present. distilled water, which is mixed with 2 c.c. of the alkaline A hydrogen vacuum seems neither more nor less favour-solution ; then we pour drop by drop the solution of able to the phenomena than does a water or an iodine iodine until we obtain a spot on the starched paper.

If moisture be present to begin with, it is with a solution of iodine, containing 4 grms. iodine per necessary to allow the vapour to be absorbed by the litre, the correction is commonly from o'i c.c., but the sulphuric acid of the pump, and to continue the exhaus- greater or less purity of the carbonate of soda may pertion with repeated warming of the apparatus until the haps affect this correction very slightly. For o'oi grm. of aqueous vapour is removed; then only do I get the best tannic acid dissolved in 1o c.c. of water we must generesults. When pith surfaces are used at the extremities rally use 10'5 c.c. of the solution of iodine at 4 per thousand. of the glass beam, they should be perfeâly dry; and they Under the influence of iodine the alkaline solutions of are more sensitive if the apparatus has held a vacuum tannin, even diluted, take a colouration so intense that it


Dec. 1, 1876.
Estimation of Potassium as Acid Tartrate.

231 would not be possible to seize distinctly the colouration of the gallate and the tannate of copper contained all the iodide of starch if we added starch paste to the tanniferous extractive matters, save a small quantity of brown acids liquid. This is why I have recourse to a leaf of white which the acetate of copper had precipitated. Having filter paper, which I cover by friction with a slight layer shown that in the decoction of oak bark it is only tannic of powdered starch. The spots made on this paper with and gallic acids that absorb the solution of iodine, the half a drop of liquor containing traces of free iodine are process of titration that I propose may be employed with immediately absorbed and show the characteristic violet all safety for the assay of tanniferous matters. I have colouration, even when the liquid is deeply coloured. found that crystallised gallic acid decomposes the solution When the value of the solution of iodine is established of iodine exactly in the same ratio as tannic acid. If then with respect to a known weight of pure tannic acid, this we wish to determine separately the gallic and tannic test liquor may be employed to titrate the various as- acid, we must determine ai first the volume of the solution tringent matters, if we adopt, as the authors of the pro- of iodine corresponding to the two acids jointly; then, cesses for the determination of tannin hitherto published after having separated the tannic acid by powdered hide, have done, tannic acid as the type of the active principle titrate the gallic acid remaining in solution. On deducting of astringent matters. But, if we wish to make very from the volume of the solution of iodine corresponding exact researches, it is necessary for each variety of as- to the two acids that which belongs to gallic acid alone, tringent matter to be studied to ascertain the value of the we obtain the quantity of tannic acid.-Bulletin de la solution of iodine by means of the pure astringent prin- Société Chimique de Paris. ciple ; for example, catechuic acid for catechu-moritannic acid for fustic; for the solution of iodine acts, without doubt, like other reagents in different proportion upon divers tannic acids. The tannic acid which I employ to ESTIMATION OF POTASSIUM AS ACID establish the value of the solution of iodine is obtained by

TARTRATE.*, keeping the tannin of Pelouze at 80° in the water-bath. At this temperature a portion of tannin, about 42 per cert,

By P. CASAMAJOR. melts, agglomerates into a greyish spongy mass, which contains the impurities of the tannin with the resins; the in most cases which present themselves to the chemist, pulverulent part constitutes pure tannin and 10'5 c.c. of in which potassium is to be estimated, it is accompanied the solution of iodine at 4 per thousand correspond to by sodium, and the course usually pursued is to estimate. o'or grm. of this tannın, whilst only 9'3 of the solution of the potassium directly as platino-potassic chloride. The iodine are required to saturate ooi grm. of the gummy precipitate obtained has the advantage that its weight is matter. The titration of tannin by means of the solution very great when compared to the weight of potassium in of iodine being very rapid and very exact, I determined to combination. There are difficulties, however, connected apply it to the assay of natural astringent matters. For with the process, and there are cases in which it is not this purpose I had to ascertain whether the matters which applicable without elaborate preparation; but platinic accompany the tannin in vegetable extracts are without chloride, although expensive, is an excellent reagent, and, action on the solution of iodine. For this purpose I exhausted with 100 c.c. of distilled water 1'515 grms. of oak its use.

in experienced hands, very good results are obtained by bark, which, assayed according to Hæner's process, con

Indirect processes are also in use, one of which contained 6.5 per cent of matter fixable by hide, and I per- sists in combining potassium and sodium with either formed in to c.c. of this decoction, containing consequently chlorine or sulphuric acid, and in estimating the total o'or grm. of tannin matters, the titration with a solution quantity of salts by one operation and the quantity of of iodine of which 10'5 c.c. corresponded to o‘oi grm. of either chlorine or sulphuric acid by another operation. pure tannic acid. If the extractive matters which accompany the tannin had acted on the solution of iodine. I be calculated. Very good results are also obtained by

From these two quantities the potassium and sodium can should have had to employ more than 10'5, c.c. of this this process. solution; but in three assays I obtained the coloured

There is also a very curious indirect process due to reaction on starched paper. After having poured 9.8 c.c. Gay-Lussac, to which I call your attention because I beof the solutions of iodine, I found then 5'92 c.c. per cent lieve that it is not generally known, and because it preof tannin instead of 6.5 c.c., the value found in using

a singular example of the expedients to which Hammer's process. The discrepancy of 0:58, which the chemists have resorted to estimate potassium in presence two processes give, must be attributed to the colouring of sodium. This process, which was in use some years matters which have been fixed by the hide along with the ago in French salt petre works, and may still be in use, is tannin in the assay by Hammer's process. In a second based on the following facts :-When 50 grms. of pure experiment I treated the same decodion of oak bark with chloride of potassium are dissolved in 200 c.c. of water, an excess of powdered hide, and having separated by the temperature of the liquid falls 11:4° C. If we take filtration the hide charged with tannin, I obtained, with

50 grms. of chloride of sodium the fall of temperature 10 c.c. of the filtered decoctions, the reaction upon the will be only 1.9° C. Gay-Lussac has directed that the starched paper after having employed ?"7 c.c. of the solu: glass vessel in which the solution takes place should tion of iodine ; whilst before the action of the hide it weigh 185 grms.-a point of some importance, as the would be necessary to employ 9:8 c.c. But these I'7 c.c.

vessel must acquire the temperature of the liquid it conof solution of iodine, corresponded to 1'02 per cent of tains. To test a mixture of potassium and sodium salts gallic acid, the average quantity of this acid, which has they are brought, in the first place, to the state of chlorides been remarked in French barks. Finally a decoction of and dried, and so grms. of the mixture are taken and disoak bark was precipitated by acetate of copper.


solved in 200 c.c. of water. A decrease of temperature is tannate and the gallate of copper were separated by noted, and the proportions of potassium and sodium filtration, the filtered liquid was neutralised by carbonate chlorides are obtained from a table in which these proporof soda, then filtered anew to separate carbonate of tions are placed, opposite numbers indicating the decrease copper. 10 c.c. of the clear solution, after an addition of of temperature. If this table is not at hand, the quantity 2 c.c. of a lye of carbonate of soda, only required o'i c.c.

of potassium chloride in 100 parts of the mixture may be of the solution of iodine to produce a coloured reaction found by calling the percentage of chloride of potassium *, upon starch. This result shows very clearly that the ex.

and the deciease of temperature, in degrees C., d. Then tractive matters do not act on the solution of iodine, since

100 - x will be the percentage of sodium chloride, and we we have only employed of this solution the volume which shall havewould have been necessary if we had operated upon distilled water, and nevertheless the liquor separated from * Read before the American Chemical Society, September 7, 1876.


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