August, 1865.

M. BRECHE, an engineer, residing at Medellin, in Central America, sent me a specimen of cast iron derived from an oxidised iron mineral, reduced in a blast furnace fed with charcoal. It is white iron, in small plates, sp. gr. 7:45. Its hardness is great, and has been attributed to the presence of nickel. Upon dissolving the iron in hydrochloric acid a solution of a beautiful green colour is obtained. I soon saw that this colour was not due to nickel but to chromium.

The powdered iron is mixed with fifteen parts of bichloride. Add rapidly enough water to form a thin paste, which triturate for about half an hour in an agate mortar (when there is no objection to the introduction of a little silica, a glass mortar may by used). The diluted paste is introduced into a German flask, and kept for an hour at a temperature of 80° or 100°. Then throw it on a filter and wash with warm water. The protochloride of mercury, after being well dried in the oven, is put into a platinum boat and introduced into a glass tube communicating with a generator of dry hydrogen. Heat gradually up to a red heat in the current of gas. The protochloride is volatilised without decomposition; at least only very little mercury is

reduced.

The volatilisation of the protochloride may equally well be effected in a current of nitrogen; but independent of the fact that it is not easy to keep up a sustained current of this gas, there will always be a suspicion of the presence of a little oxygen. In this respect hydrogen offers more security, especially if the device adopte i at the Ecole Normale au Conservatoire des Arts et Metiers is employed, which consists in passing the dry hydrogen over a column of spongy platiVOL. III. No. 2.—August, 1868.

5

65.

num before it arrives at the tube containing the boat. The sponge retains the arsenic, and determines the disappearance of the oxygen which the hydrogen gas might contain.

In proportion as the protochloride of mercury disappears, the presence of carbon becomes manifest. Allow the boat to cool in a current of hydrogen, and then weigh it with the usual precautions. The carbon is voluminous, of a fine black; it lights and burns like tinder if the boat is heated a little. This is generally the case with carbon extracted from white irons, wrought iron, and steel. The graphite coming from grey cast irons only burns with the assistance of pure oxygen.

The carbon leaves an ash after its combustion. Before weighing this residue it must be heated red hot in a current of hydrogen.

From one gramme of white cast iron in large plates, I obtained

The carbon extracted from cast irons, steels, and even from the better qualities of iron, always leaves small quantities of ash. What is its origin? The silica of this ash when it comes from steel or wrought iron, in which it cannot be supposed to come from scoria, comes from silicide; but it does not represent the totality of this, because the silicium in combination with the iron, being first transformed into chloride by the bichloride of mercury, passes by the action of water into the state of silica, of which one part, being soluble, is carried away in the washings, while another part, insoluble, is left with the protochloride of mercury. It is this insoluble silica which is found after the combustion of the carbon. I have proved this by experiment.

The metallic substances submitted to the action of

bichloride of mercury should be reduced to powder. There is no difficulty in this in the case of white cast irons, for they pulverise easily. But when grey cast irons, steel, and especially wrought irons, are operated on, recourse must be had to the file to divide them, and this is an inconvenience on which I do not need to insist. A skilful analyst, M. Damour, has tried whether it is not possible to chlorinise the iron without this preliminary division. He placed, in a spiral formed of platinum wire, a small steel cylinder weighing 1'06 grammes, and then suspended it in water containing 15 grammes of bichloride of mercury. It was put in a warm place. Two days afterwards the steel cylinder had disappeared: the protochloride of mercury, &c., was collected on a filter, washed, dried, and weighed. It yielded

Carbon, &c...

Residue of silica.

Carbon..

0'012

0'003

0'009

If the silicium combined with the iron is attacked

in the cold by the chlorine of the bichloride of mercury, this is not the case with crystallised silicium. Upon triturating this with bichloride and water, so as to form a thin paste, no reaction is remarked. For the silicium to be attacked the operation must be conducted at an elevated temperature. 05 gramme of crystallised silicium, mixed with bichloride of mercury, was placed in a platinum boat, introduced into a glass tube, and raised to a red heat. The vapour of bichloride of mercury was then passed into the tube: all the silicium had disappeared in the form of chloride of silicium, and only a trace of silica remained behind in the boat.

ON THE

ADULTERATIONS AND FALSIFICATIONS OF BREAD.

BY PROF. H. DUSSAUCE,. CHEMIST.

BREAD kept for a few days experiences spontaneous alterations which render it unfit for use. Under the influence of heat, water, and acid yeasts, it often developes in that food cryptogamic vegetations of a dark green colour and a special odour, belonging to the family of mushrooms. Among these cryptogamics the most common species is that known by the name of mucor mucedo. When that vegetation is examined with the microscope, it is observed that the large tufts it forms are composed of simple pedicles, carrying at the top a globulous and membranous body, which is the receptacle. This organ is filled with grains by maturity, it is broken with elasticity in water, and the sporules which go out form a kind of beard. That plant presents different colourations, according to the degree of maturity of the sporules.

It has been observed that common rye bread, from one day to the next, was covered with a kind of red efflorescence, and emitted a very bad smell. MM. Payen and Mirbel ascertained with the microscope that this reddish substance was composed of round corpuscles, which were the sporules of a mushroom, the oidium curantiacum. These seeds, as those of the mucor mucedo, were developed on the loaves with a great rapidity, and would bear a temperature of 212° without losing their germinative property. This alteration can be prevented by diminishing the quantity of water in the bread, increasing the dose of salt, and using it twelve hours after being withdrawn from the oven.

The amylaceous matter of the bread is destroyed by these mushrooms, it is transformed into water and carbonic acid, while the mineral, nitrogenous, and fatty substances are assimilated, and feed the vegetal.

A bread which has a blackish-blue colour was prepared with flours from hard African wheat, and wheat of lower qualities from Smyrna and Salamque. Poggiale has ascertained that this bread does not contain inorganic substances, such as iron, copper, &c., and with the microscope he has found an innumerable quantity of infusoria of the genus Bacterium of Dryardin. These infusoria have not been observed in biscuits made with the same flour; the blue colouration of these infusoria was manifested only after the fermentation, the baking, and the cooling. The gluten of the flours which have produced this phenomenon was soft, coloured, disaggregated, and had a very bad

odour.

The use of bread containing moulds ought to be rejected; indeed, several cases of poisoning have been ob

Johier has sig

served by the use of moulded bread. nalised the poisoning of three animals which had eaten moulded bread. Westerhoff has made known the case of poisoning of two children who had taken rye bread containing the mucor mucedo.

Bread prepared with flours altered by caries, darnels, &c., has a brown colour and bitter taste, and a disagreeable odour. Wheat damaged by weevil, sea-water, or any other cause, gives a brown, bitter bread, not very nutritive, and consequently improper for domestic use. When bread containing darnels, &c., is treated by alcohol, and the filtered liquid is evaporated, an extract is obtained which has an acrid and bitter taste. Sometimes rice, probably boiled, is added to the paste. Bread thus prepared contains from 7 to 8 per cent more water than ordinary bread. It is then important to exactly determine the proportion of water.

Experience has demonstrated in bread the presence of legumin, by diffusing in a very small quantity of a solution of potash, containing 12 per cent of alkali, a little crumb; by a microscopical observation the tissue proper to the legumin is seen, while all the grains of starch have disappeared.

When bread containing flour of horse-beans or vetch is successively treated by nitric acid and by ammoniacal emanations, lines coloured in rose are to be That colouration often appears only after fifteen

seen.

minutes.

To ascertain potato starch in bread, examine by the microscope a little crumb, and add to it two or three drops of a solution of potash containing 175 per cent of alkali; the characteristic plates of the fecula are perceived if the bread has been adulterated with that starch.-American Artisan.

CARBONYLIC SULPHIDE.

THIS body, intermediate between CO2 and ES2, has been long foreseen. THAN has recently succeeded in forming it and in determining its properties. He first attempted its direct synthesis by passing carbonous oxide C, and sulphur vapour through a red-hot porcelain tube. A considerable quantity was thus produced, but it could not readily be separated from the excess of carbonous oxide. Moreover it was decomposed again by the heat into its constituents. Recalling then the fact that cyanic acid, by taking up the elements of water, was decomposed into carbonic dioxide and ammonia according to the equation

(ЄÐ)" HN+H2O=H‚N+€02 (in which cyanic acid is viewed as the imid of carbonic acid), Than saw that analogy required a similar decomposition for sulpho-cyanic acid thus:

(ES)" HN+H2O=H»N+€OS Experiment confirmed this theoretic view. By the action of strong sulphuric acid, the sulphocyanates take up He and yield the gas with effervescence. The method of its preparation is as follows:

Into a cooled mixture of five volumes concentrated sulphuric acid and four volumes of water, is placed in as much potassic sulphocyanate as will allow the mass to remain fluid. The evolution of gas commences spontaneously; should it become too violent the flask may be cooled by placing it in water; and if toward the close of the action it is too slow, a gas-flame may be put under it for a moment. Thus regulated, a constant stream of gas is obtained, which contains the vapour of water and of carbonic disulphide, as well as a

trace of cyanhydric acid, and probably of formic acid. It is allowed to pass through three U-tubes, the first of which contains cotton covered with moist mercuric oxide to absorb the acids, the second, pieces of unvulcanised caoutchouc to remove the ES2,* and the third, calcic chloride to dry the gas. It is then collected over mercury, upon which when dry it has no action, even after many days. The moist gas, however, covers the mercury in a few hours with a thin coating of mercuric sulphide.

As thus prepared, carbonylic sulphide is a colourless gas, with an odour not dissimilar to that of E2, but at the same time aromatic, recalling perhaps that of HS, though not at all disagreeable. It is soluble in its own volume of water, to which it communicates its odour. The taste of this solution is distinctly sweet, followed immediately by a peculiar prickly sulphur taste resembling that of HS and of SO, together. After a few hours, however, the solution exhales a strong odour of HS. It is twice as heavy as air, and may be poured from one vessel to another. It reddens litmus feebly, much more so than CO2. When ignited it burns with a beautiful blue, slightly luminous flame, yielding €0, and SQ2. It takes fire very readily, even by a spark on a match. If the jar be held with the mouth downward, the gas burns completely; but if it be reversed, and a taper be introduced, the gas takes fire, while the taper is extinguished, and again relighted at the mouth of the jar. Under these conditions the combustion is incomplete, and sulphur is deposited. A cold and dry beaker-glass held over a jet of the burning gas, shows no trace of moisture. With 1 vols, of oxygen it forms an explosive mixture. Potassic hydrate absorbs the gas completely, though more slowly than 2. Dilute acids evolve HS and C, from this solution, so that the absorption appears to take place thus:

EOS + (HKO). = K,Є0, + K2S + (II,O)2. The potash solution gives a copious black precipitate with ammonio-argentic nitrate; no trace of cyanogen was found in the filtrate.

Neither chlorine nor fuming nitric acid has any action upon the gas at ordinary temperatures. Passed over heated mercury in a bulb-tube, no change is observed, though if long boiled in the gas a trace of mercuric sulphide is formed. When sodium is treated in the same way, a white crust is produced at the common temperature, which by heating easily melts and becomes darker. At a low red heat the sodium ignites, burning with a brilliant light and leaving a black, easily fusible mass, containing no trace of sodic cyanide, thus proving the absence of nitrogen in the gas.

When passed through mercuric-ethyl, at near it3 boiling point, a violent action takes place, pure metallic mercury without a trace of sulphide is separated, and a yellow liquid is produced, having a strong garlic odour. The author supposes it to be ethylic sulphopropionate.

If heated to low redness the gas is decomposed. This fact may be used to determine its composition as follows:

Near the closed end of a U-tube, a fine platinum wire is fused, stretching across the tube. This arm being filled with the gas over mercury, and its volume ascertained, the wire is maintained at a bright red heat by means of the battery. About the wire the gas is

The success of this device is so great that Than recommends its use in all similar cases. The CS2 is completely removed.

and I vol. (22-33 c.c.) carbonous oxide weighs 28

The weight of the sulphur in the gas is......32 The gas contains therefore one atom of e, one of →, and one of S, and its formula is EOS.

Two determinations of its density were made by Bunsen's method. The first, however, was on a portion of the gas before the use of the tube containing caoutchouc; it retains therefore a trace of ES, vapour. The observed density is 2:1152 and 2-1046 in the two experiments; the calculated is 2.0833. 60 is therefore its molecular weight. These results were confirmed by direct analyses of the gas, made according to Bunsen's

methods.

From some ex

In the opinion of the author, this gas is widely distributed in nature. Because it is so easily decomposed by water into €, and H.S, however, it has generally been confounded with these substances. periments of his own, Than thinks he can assert almost positively that this compound is contained in the new and remarkable thermal spring of Harkány; and also in the cold sulphur spring of Parád, both in Hungary. He sustains this view by the fact that the water freshly drawn has precisely the odour of the gas, which recalls, but cannot at all be mistaken for that of HS; though on standing a few hours, the sulphydric acid odour appears. For these reasons it is probable that it occurs in many other sulphur springs, and it can scarcely be doubted that it could be found among the sulphur gases of volcanic action, and perhaps in those arising from organic decomposition.

It is recognised by the following reactions: Ist. Potassic hydrate deprives the gas, or its watery solution, at once, of its peculiar odour. The alkaline solution effervesces with dilute sulphuric acid, evolving HS (distinction from ES). 2nd. In acid solutions of silver or cadmium it produces no precipitate; but upon the addition of ammonia, the respective sulphides appear (distinction from HS). 3rd. Sodic nitroferricyanide has no action in neutral or acid solutions; but an intense blue-violet colour is developed by potash or ammonia. 4th. Iodide of starch is decolourised in a short time by this gas.-Ann. Ch. Pharm., Suppl., Band v., 236, Oct., 1867.

ON THE PROPOSED WATER SUPPLY FOR THE METROPOLIS.*

BY EDWARD FRANKLAND, PH.D., F.R.S.,

PROFESSOR OF CHEMISTRY, ROYAL INSTITUTION,
(Concluded from American Reprint, July, 1868, page 27.)

HAVING thus discussed the organic portion of the solid impurity of these waters, let us now turn to the inorganic or mineral portion, which may be conveniently divided, as regards its most important constituents, into three subdivisions, viz. :

Read before the Royal Institution of Great Britain, Friday, April 3 1868.

It

Tastes differ as regards hard or soft water for drinking purposes, and medical arguments have from time to time been advanced, now in favour of and now against each. It has been asserted in this country, for instance, that hard water is necessary for the formation of bone, and that the finger of Providence points to the advantage of hard water by the profusion of calcareous strata occurring in the earth's crust, whilst M. Belgrand states that the inhabitants of the hard-water districts of France notoriously suffer from carious teeth. would probably be extremely difficult to prove either of these assertions. As regards the enormous advantages of soft water for washing, cleansing, and manufacturing purposes, there is, however, no difference of opinion. In Glasgow alone the annual saving of soap only, by the introduction of Loch Katrine water, for a previous supply of very moderately hard water, has been estimated at 36,000l. Having had the opportunity of comparing a six years' experience of the soft water supplied to Manchester, with a subsequent ten years' experience of the hard water of London, I can state that the soft water was for all purposes preferred by every member of my family. On removing from Manchester to London, the repugnance to drink the hard water of the latter city was at least as marked as that which I have sometimes noticed in persons making the transition in the opposite direction.

The hardness of the London waters is chiefly what is termed temporary hardness; that is, it is caused by the carbonates of lime and magnesia, the greater portion of which is gradually deposited on boiling the water for half-an-hour. By reason of this softening of such water by boiling, temporarily hard water is considered to be less objectionable than water of the same degree of permanent hardness. My own experience leads me to the conclusion that the advantages of temporary over permanent hardness have been considerably overrated. In reality, water used for domestic purposes is, even when used hot, either not heated to the boiling point, or is boiled for too short a time to remove more than a small proportion of its temporary hardness. Thus, water drawn from the kitchen boilers of a dwellinghouse and of the Athenæum Club was usually almost as hard as the cold water with which they were supplied, as is seen from the following table :—

The amount of soap destroyed by the use of various waters for washing purposes is seen from the following table, in which certain Welsh and Cumberland waters are also introduced for the purpose of comparison :Soap destroyed by 100,000 lbs. of various Waters.

In the recent supply of water to Paris from new sources, the importance of soft water attracted the attention of the eminent engineer M. Belgrand; a close investigation of the available sources, however, soon showed that he had unfortunately but little choice, as the really soft streams of the Fontainebleau sands (the minimum hardness is however 6) and of the granite of Morvan (minimum hardness 2.2°) were mere dribblets. Of the latter M. Belgrand says:-"Sources qui donnent les eaux les plus pures du bassin du la Seine; déviation vers Paris impossible, en raison du peu d'importance des sources." Hence the river Vanne (17°-20°), somewhat softer than the Thames, was the softest available source, and having first conclusively demonstrated this, he consoles the Parisians by saying-"Les eaux du granite, du greensand et des sables de Fontainebleau, qui sont chimiquement plus pures, sont beaucoup moins agréables à boire.”

The second category of inorganic substances contained amongst the solid impurities of waters, consists of the mineral compounds constituting chiefly the skeleton of decomposed sewage or manure. The putrescible nitrogenous organic matters present in water, or in the soil through which water percolates, undergo gradual oxidation and decomposition, by which their carbon and hydrogen are converted into carbonic acid and water, and their nitrogen into ammonia, nitrous and nitric acids. The last three remain in the water, constituting a record of previous contamination with putrescible nitrogenous organic matter. But rain-water always contains ammonia, and, as Dr. Bence Jones has shown, also nitrous and nitric acids. The nitrogen in these forms in rain-water, as it finds its way into rivers and springs, amounts in the aggregate to 032 part in 100,000 parts of water, therefore this amount must be deducted from that found on analysis, as nitrogen derived