the presence of the monohydroxylated aromatic nucleus by Millon's reaction; (2) in showing the presence by means of alloxan of the group -CH, CH(NH2) COOH formed by the decomposition of albumin after exclusion of aspartic acid and other non-albuminoïd substances. N. H. M.

2

Detection of Blood Stains in Presence of Iron Rust. By E. DANNENBERG (Chem. Centr., 1886, 840-842).-The test for blood based on the formation of hæmin crystals fails when the stain is on rusty iron, in consequence of the insolubility of the compound of hæmin with ferric oxide. The following treatment, however, yields crystals which it would appear are absolutely characteristic of blood. A few drops of strong potash solution is placed on the stain, and the object is-when possible-warmed by a spirit-lamp flame. Meanwhile the stain is loosened by scraping, and the turbid liquid is transferred to a porcelain basin. There it is washed by decantation, pouring away the pale-red ferric oxide, but retaining any heavy, dark-brown, granular substance. This, after draining off the water, is treated with a drop or two of ammonium sulphide and triturated while gently warming. The solution is filtered from the ferrous sulphide, and is examined by Erdmann's method (Otto, Ausmittelung der Gifte, 6th Ed., p. 228). The dry residue on the microscope slide is treated with acetic acid-not adding so much as to escape beyond the cover-glass; the acid is then slowly heated just to incipient boiling. On examining with a magnifying power of 300-800 the presence of blood will be indicated by the appearance of elongated, rhombic plates of brown colour, but with a colourless stripe in the direction of the longer diameter. They are found usually at the edges of the drop or of the cover-glass. It appears to be difficult to produce them at will from blood alone, but in 30 experiments with the iron compound no failure occurred. The name hamidin is proposed for these crystals. M. J. S.

Dannenberg's Hæmidin Crystals. By C. AMTHOR (Chem. Zeit., 10, 1479). These crystals, obtained by Dannenberg (preceding Abstract) by treating blood mixed with ferric oxide with ammonium sulphide and water, are now shown to be simply sulphur crystals.

D. A. L.

Analysis of Hoofs and Horns. By J. HUGHES (Chem. News, 54, 314-315). The author draws attention to the importance of taking moisture into consideration when analysing hoofs and horns, as, when powdered for analysis, these substances become very hygroscopic. When determining nitrogen in such highly nitrogenous substances by the soda-lime method, the quantity of soda-lime should exceed that generally used in nitrogen combustions; it is doubtful even then if all the nitrogen is obtained as ammonia. D. A. L.

409

General and Physical Chemistry.

Red Fluorescence of Alumina. By L. DE BOISBAUDRAN (Compt. rend., 104, 330-334).-The author has obtained the red fluorescence with pure alumina after it has been strongly heated.

Alumina which has been heated at a temperature between the melting points of copper and silver gives only a trace of the red fluorescence in a vacuum, but after addition of 0.01 per cent. of chromic oxide, the fluorescence becomes much more intense. The fluorescence increases in intensity with an increase in the proportion of chromic oxide, and is very brilliant when the amount of the latter reaches 0.33 per cent. The spectrum of the fluorescence shows a nebulous band in the region of the line C.

Alumina containing about 6 per cent. of potassium oxide, after it has been moderately heated and mixed with 0.00021 per cent. of manganous oxide, shows no red fluorescence, but a feeble green fluorescence is visible, and this increases in intensity with the proportion of manganese, and becomes very brilliant when the amount of manganese oxide is 10, 01, or 0.033 per cent. If the mixture is very strongly heated, the green fluorescence becomes much more intense and is very brilliant-even when the proportion of manganous is only 0.001 per cent.

oxide

Magnesium oxide, prepared from magnesium sulphate, when mixed with 0.1 per cent. of chromic oxide, shows a brilliant red fluorescence; this is still distinct, although not so intense, with somewhat less than 0.01 per cent. of chromic oxide. The spectrum shows a nebulous band in the region of the line C. If the magnesium oxide is very strongly heated, the fluorescence becomes more intense.

Gallium oxide, prepared from the nitrate and strongly heated, shows a violet-blue fluorescence which changes to a magnificent red when 0.67 per cent. of chromic oxide is added. The red fluorescence is obtained with 0.1 per cent. of chromic oxide, and if the amount of the latter is only 0.01 per cent., the fluorescence is at first blue, but soon changes to red. C. H. B.

Phosphorescence of Alumina. By E. BECQUEREL (Compt. rend., 104, 334-335).-Some strongly ignited alumina, obtained from Boisbaudran, showed only a faint, greenish fluorescence in a vacuum, but it showed a bright red phosphorescence in the phosphoroscope when subjected to the influence of the electric arc. The rays in sunlight, &c., which excite the phosphorescence of alumina are between D and F, and from half-way between F and G to H. In a vacuum, the exciting rays are chiefly of much higher refrangibility. The results obtained by different methods of excitation are evidently very dif

ferent.

If the vacuum in a tube containing rubies is imperfect, the rubies show scarcely any trace of luminosity under the influence of the elec

VOL. LII.

2 e

tric discharge, but when the exhaustion becomes great, a brilliant red phosphorescence is observed.

It is possible that chromic oxide confers on alumina the power of absorbing different exciting rays, and thus increases its power of phosphorescence. This action would be similar to that exerted by certain dyes on photographic plates. C. H. B.

Phosphorescence. By E. LOMMEL (Ann. Chem. Phys. [2], 30, 473-487). By a method already described (ibid., 20, 847) the author has examined the light emitted by a series of 16 phosphorescent substances prepared by Dr. Schuchardt, and by Balmain's paint. The substances were placed in small mica cells, and sunlight or the electric light, filtered through two blue and two violet glasses and a solution of ammonio-cupric sulphate, concentrated on them by means of a lens. The exciting light thus contained only rays from midway between F and G to the ultra-violet. The phosphorescent light was examined spectroscopically both during illumination and subsequently. The calibration of the spectroscope is very fully described.

None of the specimens were chemically examined. Twelve of them were styled calcium sulphide, one strontium sulphide, and the remaining three double sulphides of strontium and antimony. The calcium preparations emitted light of all colours-from red to violet. The spectra obtained from them were sometimes continuous, sometimes not; but collectively they agreed in showing three well-marked and fixed maxima of luminous intensity; namely, I, for λ = 0·584 in the yellow; II, for λ = 0·517 in the green; and III, for λ = 0·462 in the blue. In individual specimens, however, sometimes one, sometimes two of these maxima were either faint or wanting; this giving rise to the various colours emitted by them. The 12 specimens may be divided into five groups according to the maxima present.

Azure-blue and bluish-violet (two specimens), three maxima present.

Blue (2 and Balmain's paint), II and III present.

Violet to rose-red (5), I and III present.

Greenish-blue (1), only II present.

Orange (1), only I present.

After illumination has ceased, some of these maxima may fade more rapidly than others, and hence the tint of the phosphorescence may change.

The spectra of the strontium sulphide (green) and of the strontium antimony sulphides (yellow) were continuous from red to violet; but each showed only one maximum of intensity. Daring illumination, this maximum was not only differently placed in each case (A = 0·542 in the green for strontium sulphide : λ = 0·556 in the yellow-green, and 0.578 in the yellow for strontium antimony sulphide), but on withdrawal of the light it appeared to move slightly towards the violet, while the spectrum rapidly faded from the two ends towards the centre.

By inserting a little screen coated with the phosphorescent substance into the eye-piece of the spectroscope, the author has also been able to examine the effect of the various rays of the spectrum on the above substances after they had been excited by a short exposure to daylight.

In every case there was a period of intensified phosphorescence in the parts exposed to the red and ultra-red rays, followed by more or less rapid extinction. As a rule, the first period was very short; but in those specimens in which the green maximum, II, was well developed, the intensifying effect lasted for a long time-sometimes for hours, and even after the red illumination was withdrawn. All calcium preparations showed, in the intensified parts, the luminous bands already described (loc. cit.) during illumination; and after the intensifying rays were cut off a dark image of the less refrangible spectrum on a bright background appeared on the screen sooner or later.

By means of the phosphorescent eye-piece, the author has also traced the rays which are most effective in exciting phosphorescence in each case. The general result arrived at is, that the least refrangible rays of the light emitted by the calcium preparations are produced by the most refrangible rays of the exciting light. The same rule holds, though less generally, for the strontium antimony preparations.

CH. B.

Comparative Actions of Heat and Solar Radiation. By E. DUCLAUX (Compt. rend., 104, 294-297).-A large number of organic compounds containing carbon, hydrogen, and oxygen were subjected to the action of heat or solar radiation in presence of air, silver nitrate, potassium permanganate, platinic chloride, auric chloride, and other oxidising agents.

The results show that all reactions of the nature of combustion which can be produced by the action of heat can also be produced by solar radiation; but several decompositions which are effected by sunlight cannot be brought about by the influence of heat alone. All the decompositions consist in the splitting up of the original molecule into simpler molecules, amongst which may be mentioned formic, acetic, and butyric acids, methyl and ethyl alcohols, and ether-compounds which are relatively stable in the conditions under which they are formed. As a rule, the same substance yields the same products, whatever the nature of the oxidising agent with which it is in contact; but to this law there are a few exceptions. Lactic acid, for example, yields acetic acid when oxidised by the action of air, but butyric acid when oxidised by mercury salts. The stable products of combustion do not exist ready formed in the original molecules, but are the result of a rearrangement of the atoms. This is shown by the fact that the same products are obtained from different substances, and also by the fact that one and the same substance may yield different products under different conditions. As a rule, the products contain a smaller number of hydrogen and carbon-atoms than the original substances, the exceptions being formic acid, which is obtained from oxalic acid, and butyric acid which is obtained from lactic acid. Potassium permanganate, which in many cases will act in the dark, yields the same products as the action of sunlight, and the compounds, which it attacks most readily, are those which are also least stable in contact with other oxidising agents. It constitutes the most convenient reagent for determining the influence of alkalinity, acidity, &c., on the rate and limit of the oxidising action. C. H. B.

Simple Form of Water Battery. By H. A. ROWLAND (Amer. J. Sci., 33, 147).—-Strips of zinc and copper, each 2 inches wide, are soldered together so as to make a combined strip rather less than 4 inches wide. This is then cut into pieces about a quarter of an inch wide, each composed of half zinc and half copper. A thick plate of glass, a foot square, is heated and coated with shellac, and to this are stuck the strips of copper and zinc which have been bent into the shape of the letter U, with the branches a quarter of an inch apart. The soldered portion is fixed in the shellac, and the two branches stand up in the air, so that the zinc of one piece comes within onesixteenth of an inch of the copper of the next one. A row 10 inches long will thus contain 30 elements. The rows being placed one-eighth of an inch apart, a space 10 inches square will contain 800 elements. The plate is carefully warmed, and a mixture of beeswax and resin is poured on to a depth of half an inch. The back of the plate is fitted into a wooden frame with a ring screwed in the centre, so that the whole can be suspended with the elements below. When required for use, the tips of the elements are dipped into a pan of water, and the battery again hung up. The space between the elements will hold a drop of water that will not evaporate for an hour. The battery is thus in operation in a minute, and is perfectly insulated by the glass and cement. B. H. B.

Sodium Dichromate Cell. By S. L. HARDING (Amer. J. Sci., 33, 61—66).—The author has made a series of comparative tests of sodium dichromate and potassium dichromate with reference to the relative constancy or powers of endurance, the electromotive force, and the resistance of the two batteries. The cells, in every case, were set up like the Bunsen battery; the proportions used being those given by the chemical reactions which take place within the cells.

Resistance.-Lodge's method was used for determining the resistance of the cells. For the sodium dichromate cell the resistance was found to be 0.4967 ohm, and for the potassium salt cell it was 0.468 ohm. The resistances of both cells could undoubtedly be reduced if occasion should demand it.

Electromotive Force.-The electromotive force of the sodium salt cell, obtained by the open circuit method of comparison, was 1.893 volts. That of the potassium salt cell was found to be 1-852 volts. The electromotive force of the ordinary Daniell cell was 1.059 volts.

Constancy. The author obtained a series of photographic records of cells set up with the two dichromates, by substituting a sheet of sensitive paper for the ground glass scale of the reflecting galvanometer (see Amer. J. Sci., 29, 374). The sodium salt cells, it was found, ran on an average fully 20 hours, or more than one-third longer than the potassium salt cells. The greater power of sodium dichromate is due to the fact that, of the two dichromates, the sodium salt can provide the greater amount of oxygen to unite with the hydrogen set free at the negative electrode. The chemical reactions for the two salts are exactly similar; the oxygen coming from the chromic