αα

a mean value of (c-c'); yet we see by representing specially the heat conveyed during positive and negative work, that this number can differ but little from the values of its expression as long as the excess is not too small. If however there remains from a large amount of work only a small positive excess, it might be difficult to show that the proportional number could not differ considerably from the values of its expression.

Finally if Mariotte's law be not strictly accurate, we may put po+ for pv and consider g as a small magnitude depending on p and v, which at the beginning of the motion is zero. In this case in place of pdv and vdp we shall have relatively

The last magnitude is cancelled and does not occur in the resulting equation. On the other hand q now becomes

(v)

Were g of the form (p)+(v) the quantity added to q would and would vanish after the restoration to the original volume. In gen ral however would produce a change in the quantity of heat, which evidently would be always small, inasmuch as a sudden or quick change ing is very improbable.-Pogg. Ann., xcvii, 30, Jan., 1856.

2. On the crystalline form and isomeric conditions of selenium, and on the crystalline form of iodine and phosphorus.-MITSCHERLICH has communicated to the Academy of Sciences at Berlin an interesting paper upon these subjects from which we shall extract the more important details. At its boiling point, viz. 46°6 C., 100 parts of bisulphid of carbon dissolves 0.1 part of selenium, which separates on cooling partly in thin transparent red and brilliant scales, partly in grains which are so intensely colored that they appear opaque and almost black; thin splinters show the transparency and color of the scales. The author obtained the largest crystals by exposing the solution sealed up in a strong glass vessel alternately to a temperature somewhat lower than the boiling point of water and to that of the atmosphere. The crystals though small were very perfect and could be measured with the reflecting goniometer.

They belong to the oblique rhombic system (monoclinic) and are rich in forms. The crystals are easily soluble in the requisite quantity of bisulphid of carbon; on heating them to 150° C. they lose their bright color and become so dark as to be almost black; at the same time they become insoluble in the bisulphid, however long they may be boiled with it. When however the crystals are fused and then rapidly cooled they are completely dissolved by the bisulphid. The sp. gr. of the crystals before heating was 4:46–4·509 at 15°, after the warming 4.7. Schaffgotsch found 4.801 and the author believes the smaller number found by himself to be occasioned by small cavities in the crystals. Hittorf has observed that when amorphous or glassy selenium is heated to 90° it rapidly becomes crystalline while the temperature rises more

than 30°. The author finds that this crystallization and evolution of heat is most beautifully observed when large quantities are fused in a flask and heated to over 217° then allowed to cool down rapidly for 20° or 30° below this temperature and kept at this point for a while in an air bath. The temperature of the selenium there rapidly rises 20° or more and the whole mass becomes granular crystalline. This selenium is insoluble in bisulphid of carbon, and must be regarded as an allotropic modification. Large pieces of glassy selenium become granular-crystalline throughout when they are heated for some time in a glass tube plunged into boiling water. The external form is but slighly changed.

The insoluble selenium has a much darker color than the soluble form even when rubbed to a not very fine powder. When amorphous selenium as obtained by reducing selenium by sulphurous acid is covered with bisulphid of carbon, it is in a few weeks completely changed into crystalline selenium which is perfectly soluble in bisulphid of carbon. Glassy selenium under the same circumstances is gradually dissolved and then deposited in small crystals. From these facts the author concludes that the granular-crystalline selenium and that crys tallized from a solution of selenid of sodium are identical and essentially different from that crystallized from bisulphid of carbon. Glassy selenium though amorphous belongs to the modification crystallized from the bisulphid.

The author has also obtained measurable crystals of iodine which, as Wollaston and Marchand found, belongs to the right rhombic (trimetric) system. A predominant form is the rhombic octahedron, the axes, a, b, &c. being in the ratio 1: 2-055: 1.505. The author's earlier investigations showed that the crystalline form of phosphorus is the regular dodecahedron. This observation is confirmed by the fact that crystals of phosphorus obtained from a solution in oil of turpentine exert no action upon polarized light and consequently can only belong to the regular system. Very beautiful crystals may be obtained by gently heating or exposing to the sunlight phosphorus contained in a glass tube either free from air or filled with a gas in which phosphorus does not oxydize. The phosphorus sublimes from one place to another and deposits itself on the cooler parts of the tube in small and brilliant crystals. Schrötter's red phosphorus presented no trace of crystalline structure.-Journal für prakt. Chemie, Ixvi, 257.

3. On the physical properties of chemical compounds.-H. Kopp has published the continuation of his very valuable researches upon this subject, and we shall endeavor to present to our readers his general results though his memoirs scarcely admit of abstracts which do them justice. After a discussion of numerous particular cases the author arrives at the following conclusion in regard to the boiling points of homologous compounds in general. Homologous compounds which belong to the same series exhibit in general a difference in boiling point which is proportional to their difference in constitution. The difference in boiling points which correspond to a difference in constitution of C2H2 is the same in very many compounds and 19°. This difference however is not found in all series when the boiling points are compared at the usual mean pressure of the atmosphere; in some it is

greater, in others smaller. With respect to the specific volumes the author, after an extended historical introduction reviewing the results ob tained by himself and communicated in a former paper, re-states these results in a more precise form and extends them by considering new classes of compounds. In this way it appears that in analogous compounds of the same difference of constitution we find the same difference in the specific volumes; for an x-fold difference of constitution there is an x-fold difference of spec. volume. The author illustrates this for a difference of constitution equal to x. C2H2 by citing the specific volumes of hydrocarbons, alcohols, ethers, acids of the acetic and oxalic series, aldehyds and acetones. Isomeric bodies belonging to the same type have (at their boiling points) equal specific volumes and consequently equal densities. Thus the spec. vol. of acetic acid, C4H4O4, is 63.5, that of formate of methyl, C4H4O4, 63'4, &c. &c. Equivalent quantities of oxygen and hydrogen may replace each other without very sensible change of volume: thus the spec. vol. of wood spirit C2H4O2 is 419-42-2, that of formic acid C2H2O4 is 40·9— 418. It must however be remarked that the substitution of oxygen for hydrogen almost always produces a more or less perceptible change of volume. Equivalent quantities of carbon and hydrogen may replace each other without any material change in the specific volumes. Thus the spec. vol. of benzoic alcohol, C14H8O2, is 123-7, that of amylic alcohol 123 6-124.4. For the spec. volumes of the elements themselves the author finds the following values; for carbon 5.5, for hydrogen 5.5, for oxygen contained within a radical 61, for oxygen outside of the radical 3.9. These four values may be brought together in the expression "The spec. vol. of a liquid CHOO at its boiling point is 5.5a+5·5b+6·1c+3·9d.”

H

H

The symbol O is here used to denote the oxygen outside of the radical, and the author computes the spec. vols. of 45 liquids in satisfactory accordance with the observations, the difference being never 4 per cent of the whole value. The author remarks that the expression above given is simply to be regarded as a useful formula of interpolation to express the relations between the constitution and the spec. vols. of bodies. The enumeration of the specific volumes of bodies containing sulphur, chlorine, bromine and iodine leads to the following conclusions. With regard to sulphur the author remarks that this element enters into organic compounds in three different ways, (1) as replacing oxygen in compounds of the water type O2, (2) as replacing carbon within a radical, (3) as replacing oxygen within a radical. In the first and second of these cases sulphur has the same spec. volume, namely 113: but when it replaces oxygen within a radical its specific volume is higher, namely, 143-14-4. It is remarkable that alcohol and bisulphid of carbon have the same spec. vol., viz. 62. For the compounds of chlorine the rules already laid down for combinations of oxygen, hydrogen and carbon also hold good. The spec. volume of chlorine must be taken as 22.8, which is very nearly twice that of sulphur. The spec. vol. of bromine is 27.8, and that of iodine 37.5. The author next directs his attention to the spec. volumes of inorganic compounds and points out the close correspondence between the spec. vols. of the

analogous compounds PC13, SiCl3, AsCl3, of PBrs and SiBrs, and of SnCl2 and TiCl2, from which it may be inferred that tin and titanium on the one hand, and phosphorus, silicon and arsenic on the other have the same specific volumes, which for tin and titanium = 18.7, and for phosphorus, silicon and arsenic 25. Antimony has a spec. volume of 33 as deduced from both its chlorid and bromid.

The author next points out the fact that the quotient obtained by dividing the specific volume by the number of equivalents in the compound is in 44 out of the 45 liquids in his table very nearly the same, namely, from 51 to 56; water being however a remarkable exception the quotient being here 4.7. A similar result is obtained for compounds containing chlorine, bromine, iodine and sulphur, and it is further shown that between the numbers thus deduced there exists approximately at least, simple numerical relations. The difficulties however in the way of admitting these relations are very serious. In the first place the mean spec. vols. of water and of bisulphid of carbon are very different from those of other substances the former being 4.7 and the latter 6-2; yet the accuracy of the determination is beyond a doubt precisely in these cases. On the other hand the quotients in question in consequence of the smallness of the numbers appear to correspond more closely than they really do, the variation being from 10 to 16 per cent. For these reasons the author prefers to retain the numbers which directly express the specific volumes and not those which express the mean spec. vols. The memoir is concluded by many judicious observations and interesting isolated facts for which however we must refer to the original.-Ann. der Chemie und Pharmacie, xcv, 1, 2 and 3 Heft, October to December, 1855.

4. On the different methods of determining the weak or strong basic properties of an oxyd. -H. Rose has published the continuation of his researches on this subject, and has obtained some valuable analytical among his various results. Of the different sesquioxyds, glucina is the only one which is dissolved by a boiling solution of sal-ammoniac. It is consequently the strongest of all the sesquioxyd bases. Alumina is easily and completely separated from lime and sesquioxyd by boiling with a solution of sal-ammoniac, a method which in principle was already employed by Deville. The same is the case with sesquioxyd of iron in both cases however all the oxyds must be freshly precipitated and not ignited. The author next studies the behavior of the various oxyds toward a solution of chlorid of mercury. In their relations to this substance all oxyds may be divided into three classes. 1st. Those which precipitate pure yellow oxyd of mercury. 2d. Those which precipitate a red brown oxychlorid. 3d. Those which produce no precipitate. The author also gives an elaborate and able discussion of the question of the true equivalent of glucina and arrives at the conclusion that this earth must be considered as a sesquioxyd.-Pogg. Ann. xevi, 436, 550.

5. On a new class of alcohols.-CAHOURS and HOFMANN have identified acroleine and acrylic acid with members of the propylene series. Their investigation may be regarded as a generalization of the results obtained by Žinin, Berthelot and de Luca, with the iodid of propylene, and they have succeeded in producing what may be regarded as the

keystone of the whole edifice, namely, the alcohol of the propylene series; the authors term this body acrylic alcohol. When iodid of propylene is brought in contact with oxalate of silver, iodid of silver and oxalate of acryl are produced, the reaction being represented by the equation AgO.C2O3+C6 HsI Agl+C6H5O.C203. The new oxalate is a colorless limpid liquid boiling at 207° C. treated with dry ammonia it yields oxamid and acrylic alcohol C6H6O2 or C6H5O+HO. The alcohol is a colorless liquid having a penetrating odor recalling that of mustard and boiling at 103°. It burns with a much more luminous flame than ordinary alcohol and mixes with water in all proportions; with potassium it gives a gelatinous mass which corresponds to potassic alcohol. This last is strongly attacked by iodid of acryl (propylene), iodid of potassium being formed while a colorless liquid is set free which is the acrylic ether C6H5O. In the same manner the mixed ethers C6H5O+C4H50 and C12H50+C6H5O may be ob tained. By distilling acrylic alcohol with the chlorid, bromid or iodid of phosphorus, the chlorid, bromid or iodid of acryl are easily prepared. With sulphuric acid acrylic alcohol forms a sulph-acrylic acid analogous to sulphovinic acid. Phosphoric acid removes two equivalents of water from acrylic alcohol, disengaging a colorless gas which is probably C6H4. Oxydizing agents readily attack the new alcohol. A mixture of sulphuric acid and bichromate of potash act very violently upon it, the products being acroleine and acrylic acid. Platinum black produces the same results. Bisulphid of carbon and potash give with acrylic alcohol a compound analogous to xanthate of potash. The authors have also prepared a large number of ethers which are remarkably well defined. The cyanate of acryl mixed with ammonia gives the body C8H8N2O2 which is thiocinnamine in which sulphur is replaced by oxygen. Heated with water the cyanate solidifies into a mass of sinapoline or diacryl-urea C14H12N2O2=C2 { H2. (C6H5)2 } N2O2 the reaction being represented by the equation

2(C8H5NO2)+2HO=C14H12N2O2+2CO2.

The cyanate is decomposed by boiling with a solution of potash yielding sinapoline which floats on the surface and a distillate which is a mixture of methylamine, propylamine and acrylamine. The authors conclude by pointing out the perfect parallelism between acrylic alcohol and common alcohol, and draw attention to the fact that the acryl alcohol forms the third member of a new series of alcohols represented by the general formula C2nH2nO2. The cyanid of acryl should furnish by the action of potash an acid homologous with acrylic acid. Comptes Rendus, xlii, 217, 4th Feb., 1856.

6. Researches on iodated propylene.-BERTHELOT and DE LUCA have continued their observations upon this substance and have obtained in the main the same results as those of Cahours and Hofmann above described. To the body C6H5 they give the name of allyl while C. and H. use the word acryl. By the action of sodium upon iodid of propylene the authors obtained iodid of sodium and allyl, C6H5I+Na C6H5+ Nal. Allyl or acryl is a very volatile liquid, having a peculiar penetrating etherial odor. It boils at 59° C. its density at 14° is 0.684, the density of its vapor at 100° is 2.92 so that the formula C6H5 corre