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CHEMICAS News,

Estimation of Colour in Water. August 25, 1876.

77 tion is made of the part absorption takes in this pheno crease of absorption, but at 220° C. there is not so much menon, probably arising from their not having studied the light absorbed as there was at 16° C. From this we subject spectroscopically; and (2) that they speak of again infer that absorption of light at comparatively low metachromes as if generating light after the manner of temperatures is not dependent upon sensible heat or vi. incandescent bodies. That absorption plays an all- bratory motion. important part will be evident from what we have said in II. Expansion by heat-i.e., decrease of density-is an Section I., and that vibratory motion has little, if any, all but universal law so far as we at present know. There thing, to do with metachromatism we hope to make clear are several exceptions, however, and many of these are in the sequel.

among the silicates. Their anomalous behaviour is, as a Our experiments demonstrate that metachromatism rule, pointed out by the colour-change, as in the case of does not depend upon the surrounding medium, for bodies the zircon. This is not always the case, for there may be exhibit the change alike in nitrogen, air, carbonic anhy- change of colour, as in the beryl, without alteration of dride, and hydrogen. It has been suggested that the density-i.e., without appreciable molecular approach or phenomenon might in some way be due to volatilisation.' recession. On the other hand, we have in olivine an A volatile body, however, exhibits the change under a example of change of density, molecular recession, with. liquid medium. Hence we conclude that it is due in some out a corresponding alteration of colour. More facts of manner to the action of heat on the internal structure of the same nature might readily be adduced, from which we the metachrome. Metachromatism is seen in solids,- infer that molar expansion of contraction is not a necesamorphous and crystalline,-in liquids, and in gases near sary concomitant of metachromatism. their liquefying points (N204 and Bra These forms of We have, so far, excluded from our list of possible matter have molecular structure in common; hence we concomitants i. and ii. a: hence we are driven to the con. attribute metachromatism to molecular alteration. What clusion, backed by facts which space will not allow us at the nature of this alteration may be we think will be mani- present to detail here, that the only necessary concomitant fest after a close consideration of certain physical facts. is ii. ß,-i.e., atomis approach or atomic recession; in Absorbed heat performs two kinds of work :

other words, alteration of atomic potentiality. i. Kinetic, sensible to the thermometer, and

From the foregoing observations we learn ii. Potential.

(1). That metachromatism arises from increased ab. a. The overcoming of cohesion, molecular reces.

sorption of light with elevation of temperature, sion, or molar expansion, as, e.g., the con

the more refrangible increment increasing at a version of ice into water, and water into steam.

greater rate than the less refrangible. This kind of work is accompanied by a change (2). That the only necessary concomitant is alteration of density.

of atomic potentiality; a change from the white B. The overcoming of chemical attraction, atomic

towards the black end of the metachromatic recession, or molecular expansion, which finally

scale signifying atomic recession, and a change ends in decomposition, as, e.g., the resolution

from the black towards the white end atomic of PtCl4 in PtCl2 and Cl2.

approach. I. It is a fact well known to mineralogists that many

(3). That where this change of potentiality goes far anhydrous silicates, after being subjected to a high tem

enough to affect chemical attraction sufficient to perature, have upon cooling permanently changed colours.

induce chemical action, then, for bodies obeying This is shown in the following tablet in each example

the law of colour sequence, a change of colour save that of olivine.

from the white towards the black end of the

scale indicates combination, and the opposite Density before Ignition. After Ignition.

order resolution into a lower compound. I. Olivine Pistachio-green, 3.389 Pist.-green, 3-378 For much help received in this study of metachromatism 2. Beryl Straw-yellow, 2:697 Blue,

2697 | our thanks are due to Dr. Frankland and Mr. Wm. 3. Topaz Sherry 3.539 Pink,

3'533 | Valentin. 4. Zircon Brown, 4:515 White,

4'540 5. Aurora-red 4:863 Colourless, 4:863

ON THE ESTIMATION OF COLOUR IN It will be noted that where colour and density are both

WATER. permanently altered, as in 3 and 4, the warm-coloured variety is less dense than the same mineral with a cold

By CHARLES A. CAMERON. colour,-i.e., the densities are in the order of the metachromatic scale, a fact we anticipated in our study of this IN " Nesslerising” water it has been proposed to use matter. This is also strikingly evident among allotropes, solutions of caramel instead of standard solutions of the notable exception being here, as elsewhere, that of ammonia for the purpose of comparison. I have, as well phosphorus. Red amorphous phosphorus is denser than as other chemists, found that the standard solution of the yellow : this very fact, however, will no doubt tend to caramel, even when it contains much alcohol, becomes, throw light on some of its other anomalies. What we after a time, turbid and useless, and also that it soon more especially call attention to here is, that bodies of changes its hue. I do not think that the use of any identical chemical composition, without even a change of coloured solution is so reliable as that of the standard density in some cases (as in 2 and 5), may at the same solutions of ammonia ; but to those who prefer the former temperature have different colours,-i.e., may absorb light I would recommend the use of coloured discs to be em. in different degrees. From this we conclude that change ployed as follows:- Fill a Nessler tube with distilled of colour is not due to alteration of sensible heat.

water and place it over a disc so coloured that on looking Perhaps we get a better illustration of the same fact in down through the column of water it may, by the reflected the behaviour of mercuric iodide. Examined spectro- light from the disc, have the colour of a solution of say scopically at say 16° C., a band of red light is transmitted, 0·005 gr. of ammonia per gallon of water mixed with the extending from B to D. This narrows as the temperature usual 5 per cent of Nessler's solution. A dozen discs rises ; in other words, there is an increase of absorption would be sufficient; but in using them, Nessler's solution up to about 140° C. The band of transmitted light now should be always of exactly the same composition. I suddenly widens, and extends to a little beyond b. As would suggest that Mr. Sutton, who is so valuable an the temperature is on the rise there is still a gradual in. ally of the chemists who have not time or inclination to * Dr. Andrews.

prepare their solutions, &c., might make a set of cylinders, + Compiled from "Some Experiments on the Density of Garnet, discs, and solutions, in harmony with the above sugges&c." (Church), Chem. Soc. Joni vo xyii., pp. 386 and 415.

tion.

78

CHEMICAL News, Development of the Chemical Arts.

{

August 25, 1876. ON SOME CHEMICAL RESEARCHES ON THE | copper and of soda. The entire furnace is surrounded PRESENCE OF COPPER IN CAST-IRON. with an air jacket and this again with a screen of masonry

traversed by flues, which has the object of keeping back a By SERGIUS KERN, St. Petersburg.

part of the heat which would otherwise be lost by radia

tion. Another portion is supplied by the heat generated It is well known that wrought-iron containing some in the process by the combustion of the hydrochloric acid. tenths of per cent of copper is red-short; meanwhile in The above-mentioned vertical drain-pipes serve to prevent some of the best irons from Siberia was found from o‘or the apparatus from being choked up with oxide or chloride to o'o3 per cent of copper. In some specimens of steel I of iron. It has been observed that when iron apparatus found 0-2 per cent of copper ; this steel was not brittle, is employed for generating and conducting the hydroand had been used with success for manufacturing steel chloric acid gas this conveys along a certain quantity of axles. The presence of copper was found in several ferric chloride, from which it cannot be freed before specimens of cast-iron coming from blast-furnaces of the entering the decomposing furnace. Here the iron is South Oural mountains. These specimens, when ex. deposited either as chloride, or, if the formation of chlorine amined and analysed, showed that the presence of copper has already begun, i.e., as soon as watery vapour is mixed. in cast-iron may amount to a higher percentage than in with the gases, as pulverulent oxide of iron upon the steel or iron without altering the quality of the metal. copper sulphate. This iron dust falls from the vertical Unfortunately it is not so with wrought-iron or steel. drain-pipes through the grating into the space below, The specimen examined was much used for castings; it whence it is easily removed. It may here, however, be filled up the moulds beautifully, and had a very handsome remarked that Deacon, according to private communicaappearance; fresh cut it had a dark grey colour. Under tions, has latterly omitted the partition walls from the the microscope small grains of copper were easily re- decomposition furnace, by which he effects a more ready marked in the mass of the metal. This peculiar sample movement of the gaseous current without any disad-. of cast-iron was carefully analysed, and the analysis gave vantage. In a Deacon's apparatus, which the author has the following average composition :

seen at work in the establishment of Kunheim, at Berlin,

the partition walls and the vertical drain-pipes had both Iron

been omitted without any detriment being observed in the

838514 Copper..

course of several months' working.

8:123 Tin

After the mixture has passed through the decomposing

I'252
Cobalt ..

furnace it consists of chlorine, water, nitrogen, super

O'501
Silicium

Auous oxygen, and unconsumed hydrochloric acid. The

09952 Tungsten

latter is condensed in an ordinary condensation apparatus,

0'125 Carbon..

charged with dilute hydrochloric acid, or water, the tem

3'001 Manganese..

perature of the gases having been previously reduced by 2'312

air-coolers. The gas is next freed from the accompany

ing water by passage through a tower filled with chioride 99*780

of calcium, or, better, through a coke-tower, down which While analysing some iron samples for copper I often sulphuric acid flows. The gaseous mixture is then fit for used, in case only traces of copper could be detected, the absorption in the chloride of lime chambers. As a matter following method :—The specimen is dissolved in hydro- of course a drying apparatus is superfluous if a watery chloric acid, and the copper and iron are precipitated by liquid is to be saturated with chlorine, as in the preparaan excess of ammonia; the mixture is boiled and filtered; tion of potassic chlorate. the blue liquor is evaporated nearly to dryness, and the

(To be continued) resulting residue is dissolved in sulphuric acid. Into this solution a piece of magnesium ribbon is placed, which, in case of traces of copper, is quickly covered with a layer of this metal; that is easily observed under the ON SOME AMERICAN VANADIUM MINERALS. microscope.

By F. A. GENTH.

Per cent.

REPORT

1. Roscoelite, ON THE

I Am indebted to Dr. James Blake of San Francisco, DEVELOPMENT OF THE CHEMICAL ARTS

California, for a small quantity of the very interesting

mineral, which he called “Roscoelite,” in honour of DURING THE LAST TEN YEARS.*

Professor Roscoe, whose important investigations have By Dr. A. W. HOFMANN.

put vanadium in its proper place among theelements.

Roscoelite occurs in small seams, varying in thickness (Continued from p. 67.)

from 1-20th to 1-10th of an inch in a decomposed yellowish,

brownish, or greenish rock. These seams are made up Chlorine, Bromine, Iodine, and Fluorine. of small micaceous scales, sometimes # of an inch in By Dr. E. Mylius, of Ludwigshafen.

length, mostly smaller and frequently arranged in stellate After the mixture of hydrochloric acid and air has left Cleavage ; soft; the sp. gr. of the purest scales (showing

or fan-shaped groups.

They show an eminent basal the regulator, by its basis, it arrives in the decomposing less than 1 per cent of impurities) was found to be 2-938; furnace. This consists of a cast-iron box in which are nine chambers arranged in a horizontal plane, each of another specimen of less purity gave 2.921; lustre pearly, them provided with a grate or false bottom at its lower inclining, to submetallic; colour, dark clove-brown to part. Upon this grating stand, in the first, and also in greenish brown, sometimes dark brownish green. the second chamber, vertically arranged drain-pipes which

Before the blowpipe it fuses easily to a black glass, have been plunged into a hot concentrated solution of colouring the fame slightly pink. With salt of phos2. mols. copper sulphate and 3 mols. sodium sulphate, phorus gives a skeleton of silicic acid, a dark yellow bead and then dried. The remaining chambers are filled with in the oxidising flame, and and emeral green bead in the fragments of bricks or balls of clay (i 5 centimetres) which reducing flame. Only slightly acted upon by acids, even have been treated in the same manner with sulphates of composed by dilute sulphuric acid, when heated in a

by boiling concentrated sulphuric acid ; but readily de*"Berichte über die Entwickelung der Chemischen Industrie silicic acid in the form of white pearly scales, and yielding

sealed tube at a temperature of about 180° C., leaving the Während des Letzten Jahrzenends."

Ca.

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CHEMICAL NEWS,
, } Some American Vanadium Compounds.

79 a deep bluish green solution. With sodic carbonate determination of the alkalies by J. L. Smith's method. it fuses to a white mass. The roscoelite which I | The V6011 given below is the mean of the two determinareceived for investigation was so much mixed with other tions. (6.) Another sample, not quite as pure as a, was substances, such as gold, quartz, a felspathic mineral, a analysed by fusion. (c.) Still more contaminated with dark mineral, and very minute quantities of one of orange impurities, was analysed by dissolving in dilute sulphuric colour, that it was impossible to select for analysis acid in a sealed tube, &c., ca is the result of this analysis, material of perfect purity. For this reason I have delayed after deducting 11.45 per cent of the impurities. (d.) the publication my results, which were obtained over Another sample was decomposed by dilute hydrofluoric one year ago, in the hope of being able to repeat my acid; the analysis was unfortunately lost except the analyses with better and purer specimens ; but I now determinations given below; the material for this give the results of my analyses because there is no pros- analysis had not been dried over sulphuric acid. (e.) pect of getting any more of this mineral, as will be seen This sample was dried over sulphuric acid for several from a letter of Dr. Blake, dated San Francisco, April 5th, weeks ; a portion, which was decomposed by sulphuric 1876, in which he says, that the mine in which it occurs acid, gave 5'37 per cent insoluble silicates, oʻ23 per cent cannot be worked any farther until a tunnel has been of gold, and 43:24 per cent of silicic acid ; the V601, was run, and that it is quite uncertain when this will be done. determined by difference. The results given below were

Although by no means perfect, my results approach obtained by decomposing the mineral by fusion :the truth and give a fair idea of the composition of the

b.

CB. d. mineral, even if the evident admixture of other minerals, Insol. silicates,

II'45

8.91 (560) perhaps over 12 per cent, does not permit one to calculate šio2

47.69 47.82 43-46 48.60 46.81 the atomic ratio of the constituents and establish the con- A1203

14:10 12.60 10:52 11976

15978 stitution of this species. There is especially an uncer- Feo

1.67 3:30 2'03 2'27

1958 tainty with reference to the quantities of silicic acid, MgO

2:43 1974 1'95

2'31 alumina, and potassa which belong to the roscoelite, or Cao

trace trace

0'23 which may have been introduced by admixtures of fel. Na2O (trace Li2O) 0:19 0'33 0'30 O‘34)

0.60 spathic and other minerals, as will appear from the results K20

5'96
7:59
8:03
5:35

8.89 given below, which show that the mineral, when decom- V7011

22'02 21'36 20:50 22'92 20'16 posed with sulphuric or dilute hydrofluoric acid generally Ignition

4'96

5*13 5:32 5'95 6o34 3.87 gives only about 6 per cent of potassa, while fusion with calcic carbonate and ammonic chloride yields from 8 to 9

100'22 101'00 100.87 100'00 per cent. Some of these uncertainties could have been removed, if a larger quantity of the mineral had been at

A mineral, very similar in composition, and perhaps a my disposal.

compact impure variety of roscoelite, is found associated Particular attention was paid to the correct determina. with the scales. It has the appearance of a massive tion of the vanadium and the form in which it exists in dark green chlorite or that of some varieties of serpentino. the roscoelite.

The analysis was made by fusion, &c., and gave :The separation of vanadium is attended with great

SiO2

46'09 difficulties, and I have not found any of the methods of

Al2O3

17:46 separation to give fully reliable results. This is in part

Feo

I'95 owing to the incomplete precipitation of the vanadic acid,

Mgo

2:18 and in part to the impossibility of washing the precipitates

Nazo

0:18 completely without loss of vanadium. It was therefore

K20

8.66 always determined by the only method which I found to

17:53 give fully reliable results—by titration with potassic per

Ignition..

6:37 manganate. After the separation from the other elements, the

100-42 vanadic acid was reduced by hydrosulphuric acid into V204, which, after the excess of hydrosulphuric acid had

II. Psittacinite, a New Hydrous Vanadate of Lead been expelled by continued boiling, was re-oxidised into

and Copper. V205 by the permanganate. I have satisfied myself by In a paper on “American Tellurium and Bismuth numerous experiments that no matter whether only a Minerals,” read before the American Philosophical Society very minute quantity of sulphuric acid is present, or a at the meeting of August 21, 1874 (Proc. Am. Phil. Soc., very large excess, the V204‘is completely oxidised into xiv., 223—231), I mention, on the authority of Mr. P. V205 by this process.

Knabe, a siskin green pulverulent mineral from the For the determination of the state of oxidation of the “ Iron Rod Mine," Silver Star District, Montana, as a vanadium in the roscoelite, a quantity of the mineral was new “ Tellurate of lead and copper.” I had at that time dissolved in dilute sulphuric acid in a sealed tube at a no opportunity to examine into the merits of this mineral, temperature of about 180° C., and was titered after cool having mislaid the small sample which he had sent me. ing; the liquid was then reduced by hydrosulphuric acid, On receiving a copy of my paper Mr. Knabe furnished me and after boiling off the excess of the latter it was again with several specimens, which gave me a sufficient quantitered. From the quantity of oxygen required for oxida. tity of fair material for an analysis. A qualitative ex: tion in both cases it was found that vanadium in the amination proved it to be a hydrous vanadate of lead and mineral is present as V6011=2V203, V205.

copper and not a tellurate. The determinations of the other elements were made When I communicated this result to Mr. Knabe he by the usual methods.

gave me an interesting account of how he fell into his The finely-powdered mineral was dried (unless other- At the Uncle Sam's Lode, in Highland District, wise stated) for two days over sulphuric acid, and the occurs with the tetradymite a siskin green mineral, which different samples gave the following results :

has not yet been analysed, but which appears to be a (a.) Purest Scales.-The analysis was made by dis- tellurate. It looks exactly like the pulverulent variety of solving one portion in sulphuric acid and determining in the psittacinite from the Iron Rod Mine. When Mr. this the quantity and state of oxidation of the vanadium, Knabe dissolved the latter in hydrochloric acid, the the silicic acid, and insoluble impurities. The latter were evolution of chlorine indicated the presence of a higher left behind in dissolving the silicic acid in sodic carbon oxide; the solution precipitated with an excess of am. ate and gave o‘85 per cent; a second portion was decom-monic sulphide gave sulphides of lead and copper and a posed by sodic carbonate and nitrate, and a third for the filtrate, which, on addition of an acid, gave a black pre

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41:36

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80
Pseudo-Sulphocyanogen.

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August 25, 1876. cipitate-vanadic sulphide—which he mistook for tellur-, is produced. When first obtained this substance was ous sulphide.

supposed to be the radicle sulphocyanogen, but it was Psittacinite occurs in very thin cryptocrystalline always found on analysis to contain a small and somecoatings, sometimes showing a small mammillary or what variable amount of hydrogen, which excess of botryoidal structure, also peruverlent ; colour, siskin chlorine will not remove; hence it is termed pseudo-sulgreen, sometimes with a grayish tint, to olive green. phocyanogen. Before the blowpipe it fuses easily to a black shining The action of chlorine, for instance, is not completely mass. With fluxes gives the reactions of vanadium, lead represented by the equationand copper. Soluble in dilute nitric acid, the solution yielding on evaporation a deep red mass.

2NH SCy+Cl2=2NH4C1+2SCy; As it was impossible to get any of the mineral in a pure

some secondary reaction taking place by which hydrogen state, I had to use coatings with quartz attached to them, is introduced. sometimes contaminated with a little limonite; but these admixtures could not influence the analysis farther than this substance in a pure state or of a definite composition

From some experiments made some time ago to obtain very slightly with reference to the amount of water which it would appear that the hydrogen is not the only element it contains.

which varies in its amount in differently prepared The following are my results :

specimens.

Slight variations in the temperature and strength of the РЬО

solution of sulphocyanate employed producing compara50°17 42.89 27'12

42:38 Cuo

tively considerable differences in the composition of the 14:34 16.66 14'72

9*75 V205

14.64 19'05 15.87 9.96 15977 H20 7:42 not deter.

When ammonio-sulphocyanate is acted upon by chlorine

7:25 in excess for some days the filtrate from the yellow pre. SiO2 15:13

15:57 Al2O3 I'29

3.83

cipitate still gives the sulphocyanide reaction with ferric Fe2O3 2'72 7.60

salts, and no chloride of nitrogen has been produced, even

2:19 48.84 Mgo

4'00 when the action of chlorine was continued on the same

0.65 Cao not deter.

solution for more than a week. (NH4C1+Cl2 will yield Oʻ15

the nitrogen chloride in half an hour.) The oxygen ratio of PbO : CuO : V20, : H20 in the

NH4SČy solution absorbs chlorine rapidly with rise of above analyses is in

temperature. When the containing vessel is kept cool

(10° to 15° C.) and the chlorine not used in excess a light 2'97 : 2.89 : 6:41 : 6:59

yellow precipitate is produced, which, after washing with 3.60 : 3:36 : 8.34 :

hot water, in which it is slightly soluble, appears to under. 3'08 : 2097 : 6.95 :

go a decomposition. It gave, on analysis, the following
d
I'94 : 1'96 : 4:36 :

figures:-
3'04 : 3.03 : 6'90 : 6:44
: 0'97
: 2:16
2:19

с

20:53 (mean of two)
I'O0 : 0.93
2'31

H
1078 (

).
1'00 : 0.97
2'26 :

S

53.85 ( three)
d
I'00 : I'OI
: 2925

N

(23:40) 1'00 : 1'00

: 2:27 The average of the five analyses gives the ratio of

With these figures the formula CNHS agrees sufficiently

well, but the tripled formula, C3N3S3H3, seems to agree : 0.98 : 2.25 : 2.15 better with its decomposition by heat product, mellone. 9:00 : 9:00

: 18.00

The tripled formula is perhaps better written thus :corresponding to3(3PbO,V20s)+(3CuO,V203)+6(CuO, H20)+12H20.

N-N giving the following percentage :

C" | N/"C
Pbo

H- SH
53:15

H-S

S-H
CuO

18.95

19'32 H20 8:58

H

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Psittacinite occurs, sometimes associated with gold, A considerable amount of hydrocyanic acid is given off and small quantities of cerussite, chalcopyrite, and from the substance when suspended in the solution which limonite upon quartz, at several of the mines in Silver has been submitted to the action of chlorine. But after Star District, Montana, especially in the Iron Rod Mine washing and drying at 100° C. no HCy is given off when and New Career Mine, and its occurrence in these mines suspended water or in dilute acids. is looked upon as a favourable indication, for, when it is The pseudo-sulphocyanogen may possibly be utilised as met with, the vein becomes immediately, or soon after; Shades of yellow and is exceedingly permanent, requiring

a water or oil colour. It may be obtained of several rich in gold. This mineral has been called "psittacinitefrom psittacinus, siskin or rather parrot green.-American a high temperature for its decomposition, and is not altered Fournal of Science.

by the action of light either in a dry or moist condition. University of Pennsylvania, Philadelphia,

It is also unaffected (as far as the experiments have con. May 16, 1876.

tinued) when ground up moist with plumbic, bismuth, and argentic nitrates, and argentic sulphate. Mixed wet with solid argentic nitrite and exposed to sunlight a blackening

occurs, but only due to intermixed reduced silver. PSEUDO-SULPHOCYANOGEN (CNSH).

Further experiments on the action of salts on this sub

stance aided by sunlight are in progress, and the results, It is well known that when sulphocyanides, more espe. notice.

with your permission, will form the subject of a future cially the alkaline salts, are treated with chlorine, bromine,

W. R. H. or iodine, a yellow body almost entirely insoluble in water Royal College of Chemistry.

CHBMICAL NEWS,
August 25, 1876.

}

Platinum Combustion Tubes.

81

on

ON SOME OF THE CHANGES IN THE

CORRESPONDENCE.
PHYSICAL PROPERTIES OF STEEL, PRODUCED
BY TEMPERING.

ON THE PRESENCE OF ARSENIC IN THE
By A. S. KIMBALL,

VAPOURS OF BONE-MANURE. Prof. of Physics in the Worcester Institute of Industrial Science.

To the Editor of the Chemical News. A few interesting, and, to a certain extent, novel results, Sir,- In the CHEMICAL News (vol. xxxiv., p. 68) you have recently been developed in our laboratory, which i criticise a book bearing the above title. In the course of venture to present in their present incomplete form, since your remarks you say :-" Miasms or organic poisons the pressure of other duties will postpone, for a few could scarcely meet with a more efficient corrective than months, further investigations in this direction. Up to chloride of arsenic, fuorine, and other of the volatile the present time the larger number of our experiments compounds said to be given off

. On the other hand, sul. have been made upon the behaviour of tempered bars phuretted hydrogen and sulphide of ammonium are under a transverse stress, although a few qualitative trials admirably calculated to purge the atmosphere of arsenical have been made upon changes in electric conductivity and fumes.". coefficients of expansion.

I wish, as this opportunity presents itself, to lay before I. The modulus of elasticity decreases as the hardness of contradi& the suggestion that sulphuretted hydrogen

you a fact repeatedly observed, which seems calculated to the steel increases ; in other words, the harder the bar would form a purge for an atmosphere contaminated with the greater the deflection produced by a given weight. arsenical fumes. The same fact would throw some doubt

Many manuals of practical mechanics give a higher on the other suggestion, viz., that trichloride of arsenic is modulus for tempered than for untempered steel. a corrective for miasms and other organic poisons. Reuleaux, in “ Der Constructeur" (p. 4), states that it

While making some experiments on the purification of may be increased 50 per cent by hardening. Coulomb hydrochloric acid from arsenic, the late Mr. Henry Deacon and Tredgold state that hardening has no influence what suggested to mix the arsenical hydrochloric acid in the ever, while Styffe finds that the modulus is diminished. gaseous state with gaseous sulphuretted hydrogen, For our first experiment, five pieces of good tool-steel, Accordingly, some gaseous hydrogen chloride was mixed each 13" long, were cut from a half-inch square bar. with arsentrichloride and sulphuretted hydrogen, in one These were carefully annealed, squared, and polished. case in as dry a condition as the use of concentrated sul. No. i was laid aside, and the others were hardened in phuric acid will permit, in another case saturated with cold water in the usual manner; No 2 was “ drawn "

aqueous vapour. In the one case, when the gaseous mix. a hot plate to a dark blue ; No. 3 to a purple; No. 4 to a ture was dry, no trace of sulphide of arsenic had deposited straw-colour; No, 5 was left hard. The modulus of elas. on the side of the glass vessel containing the mixture; ticity was then determined by measuring the deflection in the other case, in which some liquid hydrochloric acid produced by a weight applied at the middle of the bar. was introduced into the vessel, so that its sides were wet, The probable error of the experiments did not exceed one- a little chloride of arsenic had been decomposed and fifth of 5 per cent. The experiment was varied in many deposited as sulphide. In both instances, however, large ways; several qualities of steel and bars of different di- quantities of sulphide of arsenic were formed when the mensions were employed with uniform results. In some gaseous mixture was driven through a wash-bottle congrades of steel a difference of more than 10 per cent has taining water. been found between the modulus of the hardened and The experiments were repeated constantly with the that of the annealed bar,

same result. The conclusion is that gaseous arsentri. II. The increase of deflection in a given time is greater

chloride does not react upon gaseous sulphuretted hydrogen. the harder the steel.

You will readily admit that sulphuretted hydrogen will

form no purge for an atmosphere contaminated with It is well known that the defle&ion of a bar left under arsenical fumes, and you will doubt with me, seeing that stress will increase for a long time. I am not aware, chloride of arsenic will not act in the gaseous state upon however, that comparative tests of the rate of increase in sulphuretted hydrogen, whether arsentrichloride will, steel of different tempers have previously been made. under those conditions, correct the noxious miasms or III. The immediate set increases with the hardness of the

organic poisons.-I am, &c,,

DR. FERD. HURTER. steel. In the experiments each bar was of course loaded with

Laboratory of Messrs. Gaskell, Deacon, and Co.,

Widnes, August 19, 1876. the same weight, which was allowed to act for the same number of minutes. IV. A bar recovers from a temporary set with greater

PLATINUM COMBUSTION TUBES. rapidity the harder it is. The remarkable Auctuations in the line of the bar ob.

To the Editor of the Chemical News: served by Prof. Norton (Amer. Fourn. of Science and Arts, SIR,—Your correspondent, writing on the subject of pla. April, 1876) became more marked and had a wider range tinum combustion tubes in the CHEMICAL News (vol. as the hardness of the bar increased. In none of the ex. xxxiv., p. 67), says :-"With a platinum tube filled with periments referred to was a permanent set produced, cupric oxide in the manner above described it would be though in some cases forty-eight hours had elapsed before possible to perform a succession of analyses; thus greatly the bar recovered its original line. In a few experiments economising time. This arrangement of apparatus is an attempt was made to determine

the approximate hard based on purely theoretical considerations. I have had ness of the bars by grinding. The results obtained, no opportunities of pradically testing the value of platinum however, could not be considered very reliable. A more combustion tubes." satisfactory method was found in the determination of the I am happy to be able to supply the practical experience temperatures employed in hardening and drawing, by the which C. J. H. W. lacks. In a paper on the “Determina. specific heat of platinum, or by the use of the pyrometer. tion of Carbon in Steel,” published in the Fournal of the

I am indebted to Mr. F. C. Blake for the accuracy with Chemical Society, for Oaober, 1870, I state that a pla. which the experiments referred to in this note have been tinum tube was employed, and that " I was thus saved conducted.-American Journal of Science and Arts, from the annoyance caused by the fusing or cracking of

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