Зображення сторінки
PDF
ePub

The composition of the yolk of the fowls' | nitrogen and known as being highly nutri

[blocks in formation]

Cholesterine....

0.438

Lecithine...

8.426

Cerebrine..

0.300

Hydrochlorate of ammonia....

0.034

Chlorides of sodium and potas-
sium, and sulphate of potassa
Phosphates of lime and magnesia
Extract of meat.....
Coloring matter, traces of iron,
&c. &c.....

0-277

1.022

0.400

0.553

100.000

tious. The species used was Agaricus prunellus, a species which is edible, and remarkable for forming most beautiful fairy rings.

After having separated all soluble proteïn compounds by means of basic acetate of lead, which throws them down completely, the amount of nitrogen remaining in the | juice of these agarics, in the form of ammoniacal salts, was found to be 0.204 per cent. for the fresh fungi, or 1.820 per cent. for the dried fungi. The whole amount of nitrogen in the same agarics, collected at the same time, determined by combustion, was found to be 0.740 per cent. for the fresh fungi, or 6.610 per cent. for the fungi dried at 212° F. Deducting from the last stated numbers the quantity of nitrogen found to exist in the juice in the form of ammonia, we find that only 0.536 per cent. of nitrogen in the fresh, or 4.799 per cent. of nitrogen in the dry fungi, exists in the state of proteïn compounds, and that nearly one-third of the nitrogen obtained by direct combustion exists in the form of ammonia in the juice, or at all events in a form in which the nitrogen adds The eggs of fish, as is known, are fecund nothing to the nutritive value of the fungi. only after laying; consequently, the prin- The nutritive value of fungi has, therefore, ciples which they contain are not the product been considerably overrated; and there can of fecundation. Does this physiological act be little doubt that the same is the case with change their chemical composition? It many vegetables, which, according to the appeared to me that this interesting study author's experiments, contain sometimes should be preceded by the examination of considerable quantities of ammonia in the the soft roe itself, a necessary agent of form of ammoniacal salts. fecundation. I will in my next memoir make known the result of my researches on the nature of this substance.

Such are the results which I obtained in the researches which I have made on the eggs of the carp; they lead us, as may be perceived, to regard fishes' eggs as containing the same elements as those of birds. The principles which constitute the eggs of these two classes of animals vary, it is true, in their relative proportion, but that is probably owing to their being developed in different media.

Dr. CHRISTISON remarked that he had long been convinced that there was a considerable fallacy in the methods of determining the value of nitrogen, and he hoped Dr. Völcker's communication would lead

ON THE PER-CENTAGE OF NITRO- inquiry into a more satisfactory direction.

GEN AS AN INDEX TO THE
NUTRITIVE VALUE OF FOOD.

BY DR. A. VÖLCKER.

THE purpose of this paper was to show that the usual estimation of the nutritive qualities of an article of food is frequently attended with inaccuracies, consequently it is desirable to modify our present methods in this respect in many cases.

One circumstance which leads to considerable error is, the presence of ammoniacal salts in the juices of plants. In order to prove experimentally the presence of ammoniacal salts in larger quantities than hitherto suspected, and to avoid the objection that they might result from a partial decomposition of albuminous substances, during the analysis, the author selected fungi for his experiments, which are rich in

Dr. DAUBENY made some observations on this paper; and particularly noticed the researches of Prof. Hoffman on the substitution of ammonia, or of its elements, for carbon, which it appeared to him pointed to some laws in connexion with the processes of assimilation of nitrogenous materials by growing vegetables.

Dr. R. D. THOMSON offered some objections to the reception of the doctrine that nitrogen was the principal source of nutrition, since it is found that blood and the other animal constituents contain many other substances.

Dr. L. PLAYFAIR was pleased that Dr. Völcker had pointed out a source of error in the determination of nitrogen. Having been engaged in examining the dietaries of a great number of extensive establishments, he should lay the results before the Meeting.

REMARKS ON SOME CHEMICAL An analysis of the glass, made by Prof. FACTS CONNECTED WITH THE Voelcker, showed the cause of change TESSELLATED PAVEMENTS DIS- from ruby to green to have been due to the COVERED AT CIRENCESTER (THE fact that the antique ruby glass had derived ROMAN CORINIUM). its color from peroxide of copper, and that the tessellæ had become covered with carbonate of copper from a decomposition of their surfaces.

BY PROFESSOR BUCKMAN.

In this paper it was shown that the materials of which pavements are composed are of two kinds :-the first derived from rocks of the district and termed natural, the second composed of clay, fictilia and glass, artificial tessellæ.

The natural tessellæ, many of which are so altered by chemical manipulation as to cause many of them to be referred to foreign rocks, consist of bits of stone from the chalk, oolite, lias, and red sandstone formations, were clearly referred to their origin, and the processes by which they were prepared for pavements were pointed out. Thus, a grey color was produced from a creamcolored oolite, the change of color being caused by a process of roasting. This is dependent upon the fact that the oolite bed of which they are made contains iron and organic matter, the latter of which prevented the iron from peroxidising, and thus the grey was due to a protoxide of that metal.

The artificial tessellæ from pottery consist of shades of red and black; all the reds being due to a peroxidation of the iron in the clays from which they were made, whilst the blacks were the result of baking in "smother furnaces," as long since pointed out by Mr. Artis, so that the carbonaceous matter of the fuel with which the baking was effected was prevented from escaping, and, as he would lead us to infer, the black smoke penetrates the clay and thus blackens it. The author, however, showed that this smoke acted chemically, by preventing the oxidation of the iron, and thus the change from the dark color of the clay to red which usually occurs in burning pottery and bricks was prevented.

[blocks in formation]

By keeping chlorine water in flasks sheltered from the light it is preserved without appreciable change; but, if this water be exposed for some time to the direct influence of the solar rays, new reactions are discovered in it. Thus, chloride of lead is converted into pure oxide, and chloride of manganese gives a black precipitate of the peroxide, whilst recent chlorine water does not affect these two chlorides in any way.

In seeking to what chloruretted combination this characteristic oxidation of the chlorides of lead and manganese belonged, I found that it resided exclusively in hypochlorons acid: this acid, CIO, may be thus recognised even in a solution of chlorine, and in very small quantity; for these two reagen's, and especially the chloride of manganese, are exceedingly sensitive.

The action of chlorine on water is evidently identical with that of chlorine on moist hydrogenous substances; it is substituted for the hydrogen of the water, and if the phenomenon is limited, it is because the hydrochloric acid in its turn destroys the hypochlorous acid, and regenerates chlorine: this reaction is represented by reversing the two members of the equation— 2C1+HO=CIO+HC1; CIO+HCI=2C1+HO.

The hydrochloric and hyponitrous acids can coexist only in presence of a very large quantity of water; I made a direct experiment on this point.

Reference was then made to a medallion of the pavement representing Flora, in the first drawing of which the head-dress and flowers held in the hand were colored ver- I think that the very simple molecular digris green, the hue these objects presented relation which exists between water and on being exhumed; but as this was unsatis-hypochlorous acid should be extended to factory in chromatic arrangement, the author suspected some subsequent chemical change, and on scraping away the green from the surfaces of the tessella in question, a beautiful ruby glass presented itself. New drawings (which were also exhibited) were then made with ruby instead of green color: the result of which was, that what was before inharmonious in color and grouping at once assumed harmony in these respects, and became perfectly intelligible.

the chloride of sulphur which figures in this system, sulphurrtted hydrogen in which chlorine has replaced the hydrogen, equivalent for equivalent. It may be conceived, by this arrangement, that the most chloruretted chloride of sulphur will contain 2 equal equivalents of chlorine and sulphur. Thus we seek in vain, as all chemists well

Annales de Chimie et de Physique, August, 1850.

know to unite more than 1 equivalent of ing potassa act on the chlorites of proteïn. chlorine to 1 equivalent of sulphur; it is, This reagent reveals to us differences which on the contrary, easy to combine several are very interesting to investigate. I have equivalents of sulphur with 1 equivalent of already ascertained that the action of chlochlorine. This corresponds with the poly-rine on albumen, until the gas ceases to be sulphurets of hydrogen: so that we have the following symmetries:

HO, HS, HSn; CIO, CIS, CISn.

ON A REAGENT FOR THE PROTEIN COMPOUNDS.*

BY M. E. MILLON.

THE very acid liquor which is obtained by dissolving mercury in its own weight of nitric acid with 4 equivalents of water, is a reagent of extreme delicacy for all the albuminoïd substances, and for many of the secondary products connected with them.

This nitro-mercurial liquor communicates to these different substances a very intense red color, and we may thus very easily detect in water Tooooo of albumen, and even a smaller proportion.

To give an immediate idea of the delicacy of this reagent, and perhaps also of the advantages which may be derived from it in the study of vegetable organisms, I may state that cotton, the feculas and gum arabic, take, on contact with it, a very distinct rose tint. Almost all urines take a rose color, after the nitro-mercurial liquor has been mixed with it, when the mixture is heated and the urea destroyed.

The albumen of the blood, that of serous tumors and of vegetables, fibrine, caseum, gluten, legumine, silk, wool, feathers, horn, the epidermis, gelatine, choudrine, proteïn, the crystalline lens, the cornea, well-washed crassamentum, and the soluble product which it yields to boiling water as well as its insoluble portion, assume a more or less deep red.

When proteïn becomes soluble by the prolonged action of alkaline leys, or by the action of sulphuric acid, the same red coloration is always produced; but it is not an insoluble matter which is obtained; the liquor reddens powerfully without giving any precipitate.

Xanthoproteic acid, the chlorites of protein and the oxides of proteïn which are derived from these chlorites, are separated from the foregoing products: they do not acquire a red color.

Thus crassamentum is not identical with the oxides of proteïn obtained by mak

Annales de Chimie et de Physique, August, 1850.

absorbed, furnishes no less than three matters very distinct from each other.

The nitro-mercurial liquor is prepared by pouring on the pure metal an equal weight of nitric acid with 44 equivalents of water.

The reaction takes place vividly without heat; when it becomes slow, it is very gently heated until the metal is completely dissolved; at this point we stop, and add two volumes of water to each volume of mercurial solution. After some hours, the liquid portion is decanted from the crystalline mixture of the nitrate and nitrite of mercury. This liquor reacts without heat on the albuminoïd substances, but the reaction is complete only at from 140° to 158° F.; it is even good to carry the mixture immediately to ebullition. A prolonged contact of an excess of reagent does not alter the red matter. I have thus kept, for more than a year, albumen turned of a very bright red in presence of a great excess of nitromercurial liquor.

It is to be observed that the reagent resides in neither the protonitrate of mercury, nor in the pernitrate of mercury, nor in their mixture. Nitrous acid must be added to the solution of these two salts; until this is done no coloration is obtained. Pure pernitrate of mercury, saturated with nitrous acid, reddens sensibly, but much less than the mixture of mercurial salts, saturated with the nitrous acid. Thus the most simple method of preparing this liquor consists in treating mercury by nitric acid according to the directions above given.

ON THE ACTION OF THE SOAP TEST ON WATER CONTAINING A SALT OF MAGNESIA ONLY, AND LIKEWISE ON WATER CONTAINING A SALT OF MAGNESIA AND A SALT OF LIME.

BY MR. D. CAMPBELL THIS was an examination of the value of the soap test of Dr. Clark. The conclusions arrived at were:

1st. That water containing sulphate of magnesia alone, acts towards the soap test in producing with it a perfect lather, similarly, or nearly so, as does water containing a lime salt alone-but only when the equivalent of magnesia salt does not exceed six grains of carbonate of lime in a gallon of

water.

2nd. That the degrees of hardness of an ordinary water cannot be inferred by the rule. Compute the grains of lime, magnesia, oxides of iron and alumina, in a gallon of water, each into its equivalent of chalk. The sum of these equivalents will be the hardness of the water.

3rd. That the degrees of hardness of a water containing magnesia and lime salts, as shown by the soap test as it is now applied, cannot in every case be taken as representing the amount of these salts in the water; nor in nearly any instance can it be considered as giving the amount of lime in a water when magnesia is present.

4th. That water might show by the soap test a small degree of hardness in comparison to the considerable quantities of salts of magnesia and of lime it might contain, and trusting to this method of analysis alone when selecting water for ordinary use and for steam purposes, might lead to a water being adopted which might not be conducive to the general health, and which would leave considerable deposits in vessels in which it was boiled-a great deterioration to its use in steam generating.

way have marked glass so as to show the faintest outlines when breathed upon. In all probability the fluoride of calcium is associated with the phosphate of lime, and, when milk is coagulated, separates along with the caseine.

Dr. Wilson also stated that he had repeated the inquiry into the solubility of fluoride of calcium in water, reported to the Association at its Southampton meeting, and with the same result, viz., that 16 fluid ounces, or 7,000 gr. of water, at 60°, dissolve 0.26 gr. of fluor spar.

ON A NEW AND READY PROCESS
FOR THE QUANTITATIVE DETER-
MINATION OF IRON.

BY DR. F. PENNY.

THE author recommends the employment of the chromate and bichromate of potassa for the estimation of iron in the common ores of the metal, and especially for the analysis of the clay-band and black-band ironstone of this country.

He was led to the application of these salts in the course of some recent investigations on the materials and products of the

PRESENCE OF FLUORINE IN BLOOD manufacture of alum from "alum-shale,"

ΟΧ.

AND MILK.

BY DR. G. WILSON.

[ocr errors]

in which he was much retarded by the want of a ready method of estimating the oxides IN 1846 I announced to the Royal Society of iron. The chromates of potassa give of Edinburgh that after finding that fluor very accurate results, and possess the great spar was soluble in water, and occurred in advantage that a much larger quantity of many natural waters, I thought it well to material may be operated on than can be seek for it in milk and in blood, and found conveniently treated by the usual methods. distinct evidence of its presence in both. For practical purposes, he says, the bichroThe proofs were not so decisive as I could mate is to be preferred. The process have desired. This summer, however, I requires no other apparatus than that comhave employed the fresh drawn blood of the monly used for centigrade testing, which is About 26 imperial pints or 3 gallons familiar to all persons engaged in chemical of blood were made use of. From the large pursuits. It may be easily and rapidly scale on which the experiment was con- executed, occupying only a fraction of the ducted, and the simplicity of the process time required for the process of estimating followed, the evidence in favor of the pre-iron by precipitation as the sesquioxide; sence of fluorine in the blood of the ox appears unexceptionable; and it cannot be doubted that the blood of other animals will be found to contain the same element. I presume it to be present in the state of fluoride of calcium, and that its amount is very small, but I have not attempted its quantitative determination.

and it is not interfered with by the presence of alum and phosphates which usually exist in the ore. The method is based on the well-known reciprocal action of chromic acid and protoxide of iron, whereby a transference of oxygen takes place, the protoxide of iron becoming converted into sesquioxide and the chromic acid into sesquioxide of chromium.

Milk was examined in a similar way, with nine imperial pints of rich milk from a country farm. The vapor which they evolved etched glass distinctly. The ashes of 12 PHOSPHORESCENCE OF POTASSIUM. lb. of new skimmed-milk cheese, made this spring, treated in the same way occasioned deep etching of glass. The ashes of four imperial pints of whey treated in the same

BY MR. W. PETRIE.

WHILE speculating on the consequences of the dynamical theory of heat, I was led to

the conclusion that cold potassium ought to be found luminous; and farther, that it ought to be only about a tenth part as luminous as phosphorus.

ses a very powerful basic reaction. This solution, saturated with hydrochloric acid, and afterwards evaporated on a sand-bath, leaves a very crystalline salt, which readily dissolves in absolute alcohol. Bichloride of platinum, added to this solution, gives rise to a beautiful yellow precipitate. The ana

On testing this experimentally, with the precautions for sensitive vision which the anticipated feebleness of the light indicated to be necessary, the result was, that onlysis of this salt gave results corresponding dividing a bit of potassium (which was quite dry, being protected only by a coating of bees' wax), the halves showed two distinctly luminous sections; the light being about a tenth of that from a similar surface of phosphorus, as far as the eye could make the comparison. The light diminished, naturally, as a protecting coating of oxide was formed, but remained just perceptible to the most sensitive sight, as long as half an hour.

to the formula C2H3NHCI Pt CP2, whence it results that the base is the methylamine of M. Wurtz. I had already established the formation of methylamine by the action of potassa-lime and soda-lime on codeïn in the memoir I have already mentioned. This base appears to be the only product of the action of potassa on the yellow acid, but I have ascertained that the action of potassa-lime on codeïn itself determines the formation not only of methylamine, but also of another base, C6H9N, propylamine.* appears, therefore, that there exists a certain

It

ACTION OF NITRIC ACID ON THE analogy between the action of soda-lime and

ORGANIC ALKALIS.

BY DR. THOMAS ANDERSON.

IN pursuing the investigations on codeïn which I submitted to the Royal Society of Edinburgh, I was led to observe some very remarkable phenomena which result from the action of nitric acid on this substance, and which appear to be common to all the organic bases, to all those, at least, which I have hitherto had an opportunity of examining.

that which nitric acid and potassa successively exert on this base. I do not dwell on this point at present, but shall return to it in the course of my investigations.

NARCOTINE forms with nitric acid a great variety of products which depend on the concentration of the acid. If we operate at a low temperature and with a very dilute acid, derived bases are obtained which I have not yet examined; but by the action of a more concentrated acid, a yellow resinous acid is formed. If this acid be treated by a solution of potassa, a volatile base is disengaged, which, with the salt of platinum, gives results corresponding with methylamine.

MORPHIA and STRYCHNIA, by the same treatment, give volatile bases which I am now engaged in examining.

The action of nitric acid on PIPERINE is very energetic; vapors of nitrous acid are abundantly disengaged, accompanied by a peculiar odor resembling that of bitter almonds. A brownish resin is formed, one portion of which floats on the surface, and the other remains dissolved in the excess of nitric acid, and from which it may be

If codeïn be treated with very dilute nitric acid, a substituted base, nitrocodeïn is obtained; if, on the contrary, the acid be of medium concentration, a very violent action takes place, accompanied by a disengagement of nitrous vapors, from which results a solution of an orange color, depositing, when water is added, a resinous acid. If the nitric acid be evaporated by heating on a sand-bath, the new acid is obtained under the form of a yellowish porous mass, readily soluble in alcohol, from which it is reprecipitated by water. I have not yet completed the analysis of this substance; nevertheless the results obtained appear to indicate a formula derived from codeïn by the substi-precipitated by adding water. tution of NO1, and the addition of several By evaporating the excess of acid on a equivalents of oxygen. If this acid be treated by a dilute solution of caustic potassa, it is dissolved, giving to the liquor a deep red color, and if it be boiled, a volatile base of a very powerful and peculiar odor is disengaged, which base is obtained, by distillation, in the water of the receiver. The liquid which distils over is of an odor at once penetrating and putrid, and disengages white vapors when a rod wetted with hydrochloric acid is held near it; it posses

sand-bath, a brown residue is obtained, which dissolves in potassa, with a magnificent blood red color. By boiling, a volatile base of a peculiar and aromatic odor is

* I may observe that my experiments concerning the action of soda-lime on codeïn were made before I had seen the Note of M. Wertheim, published in the No. of the Annalen der Chemie und Pharmacie for February, 1850.

« НазадПродовжити »