208 



NA TURE 



\_Dcc. 30, 1880 



nearly realised, but the gradual absorption, by the liquid, of 

 reduction products, tends to cause a deviation from this result. 



Berthelot has recently studied [Compt. rend.'] the action of 

 air and of hydrochloric acid in presence of air, on pure mercury. 

 He confirms the generally accepted fact that pure mercury is 

 very slowly and superficially oxidised by the action of air at 

 ordinary temperatures. If gaseous hydrochloric acid is shaken 

 with mercury in presence of air mercurous chloride and \\ ater 

 are produced. This reaction (irg., + 2UCl+ = HgXl„ + II.,0) 

 is attended with the evolution of 53,400 thermal units, whereas 

 the oxidation of mercury (llg + O = HgO) is attended with 

 the evolution of only 21,100 units. The action of hydrochloric 

 acid in presence of air on copper (Cu, + 2HCI + O = 

 Cu.iClj 4- H„0) is accompanied by the evolution of 26,500 

 thermal units^ hydrochloric acid in absence of air is, as is well 

 l;nown, almost without action on metallic copper. 



In the course of his investigation into the action of phosphorus 

 on hydriodic acid, Damoiseau (Compt. rend.) describes a method 

 for preparing phosphonium iodide in a .'■tate sufficiently pure for 

 general use. Ten parts ordinary phosphorus in small pieces are 

 allowed to react for .come time on twenty-two parts of an aqueous 

 solution of hydriodic acid (saturated in the cold) ; two parts 

 iodine are added, and the phosphorous acid which is produced is 

 separated from the crystals of phosphonium iodide by washing 

 vfith aqueous hydriodic acid. 



A SERIES of compounds, derived from monohydric alcohols, in 

 which the " hydroxylic hydrogen " of the alcohol is replaced by 

 aluminium, is described (Client. Ncii<s) by Gladstone and Tribe. 

 These bodies are prepared by the action of aluminium in presence 

 of aluminium iodide on the alcohol. The new substances are 

 solids, melting to clear liquids which do not solidify at tempera- 

 tures much below the melting points of the solids ; they are 

 decomposed by water with formation of aluminium hydrate and 

 the corresponding alcohol. 



The sulphides of vanadium have been investigated by Kay 

 (Cheui. Soc. Jtuirn.). The compounds obtained by Berzelius by 

 the acticn of sulphuretted hydrogen on solutions of van.adium 

 salts are shown to contain oxygen in addition to vanadium and 

 sulphur, but no definite formula can be assigned to any of tlie-e 

 bodies. Vanadium trisulpLide V^Sj is obtained by the action of 

 dry sulphuretted hydrogen on "heated vanadium trioxide, as 

 described by Berzelius. When this compound is heated to bright 

 redness in hydrogen, it is reduced to the disulphidt VoSj, and 

 when heated with sulphur to 400° it is converted into the 

 pentasulphide V2S5. 



In the Chem. Soc. Journ. Kingzett describes experiments on 

 the atmospheric oxidation of phosphorus which seem to prove 

 that ozone and hydrogen peroxide are simultaneously produced 

 when air is draw n over phosphorus partially immersed in water. 

 Many so-called basic sulphates of iron have been from time 

 to time described : of the fifteen which are generally recogni;ed 

 as probably existing it would appear from PicUering's experi- 

 ments (Chem. .Soc. Journ.) that only one, viz. 2Fej03 . SO^, 

 actually exists. 



Dr. Sydney Marsden has recently experimented on the 

 action of boron on various metals at high temperatures. He 

 finds (Proc. R. S. Edin. and Chem. Soc. journ.) that silver dis- 

 solves amorphous boron, and that on cooling, pure boron is 

 obtained partly in the graphitoidal, partly in the adamantine 

 form. Copper combines with boron to form the compound 

 B2CU.3. 



Prof. Bellati has published in pamphlet form, under the 

 title " Proprieta termiche notevoli di alcuni loduri doppi," an 

 extended and careful series of observations of the specific gravities, 

 specific heats, thermal expansions, and thermal changes which 

 accompany changes of colour and structure, of several douljle 

 iodides of mercury, more especially of the lliree salts Hgl„ . 2Agl, 

 HgL . 3AgI, and HgU . CujTj. 



Herr Haass describes in the Berliner Berichte a simple 

 method of illu-trating the existence of the so-called "critical 

 pressure" described in this journal by Carnelley. A small piece 

 of mercuric chloride is placed in a glass tube which is closed at 

 one end, and communicates at the other with a Bunsen pump. 

 So long as the manometer registers less than about 400 mm. 

 pressure it is not possible to melt the mercuric chloride by heating 

 it ; the salt passes at once from the solid to the gaseous state. 

 But immediately the pressure rises above about 420mm. the 

 mercuric chloride melts. 



In studying the condensation products of aldehyde Prof. 

 Lieben has obtained ( IVied. Akad. Ber.) a new alcohol belonging 

 to the same series as glycerin, viz. C4H-(OH)3. The new com- 

 pound, called butenyl glycerin by Lieben, is a syrupy, sweet- 

 tasting hquid, soluble in water, boiling at 172°-! 75° under a 

 pressure of 27 mm. It forms a triacetin analogous in properties 

 to the natural fats ; when heated with oxalic acid its behaviour is 

 similar to that of glycerin : formic acid is produced along with 

 an oily, strongly-smelling substance which has not as yet been 

 fully examined. 



PHYSICAL NOTES 

 Mons. a. Angot proposes a new formula for calculating 

 altitudes from barometric observations, based upon that givei» 

 originally by Laplace. The existing method of calculation from 

 observed monthly or annual means is found, as Plantamour has 

 shou n, fo be defective, since its results exhibit an uncertainty 

 that varies with the season, an elevated station appearing to be 

 higher by day and in summer than at night or in winter. As an 

 example, when the height of the Great St. Bernard is measured 

 by comparison of barometer observations between that place 

 and Geneva, it would appear that the height of the Great St. 

 Bernard exhibits a diurnal variation of 17 metres in winter ami 

 of more than 47 metres in summer ; while the mean of the June 

 observations gives a height of 25 metres higher Ihan that found 

 from the January numbers ! These anomalies M. Angot ex- 

 plains by the facts that the mean temperature between the sta- 

 tions is not exactly equal to the half sum of the two temperatures, 

 and that the weight of the air between the two .stations is on the 

 other hand greater when the mean temperature is low. The 

 rather complicated formula proposed by M. Angot gives the 

 difference in altitude by calculating directly the height of each 

 station above an imaginary plane at w hich the barometric pres- 

 sure is equal to 760 miUims. No empirical coefficients are 

 needed in this case, the standard constants of Regnault and 

 others for air and aqueous vapour being taken. M. Angot has 

 recalculated from his formula a new set of tables, involving all 

 the corrections that must be applied to the older tables of the 

 Bureau des Longitudes. 



In a recent number of the yournal de Genive M. Colladon 

 has pointed cut that a poplar or other tall tree may, if its roots 

 strike into damp soil, serve as a lightning-conductor to protect a 

 house ; and he thinks he has verified this conjecture by examin- 

 ation of a number of individual cases of lightning-stroke. In 

 the case however where the house stands between the tree and a 

 piece of water, a pond or a stream, the shortest path for the 

 lightning from the tree to the wet conductor may.be through the 

 house ! 



VvoN ZoCH has described a new kind of electric dust-figures, 

 which he regards as having an important bearing upon the theory 

 of dii^charges in vacua, being in opposition to the vie.vs of 

 Crookes. Tubes of i to 3 centims. diameter, and from 10 to 30 

 cenlims. in length, were closed at both erids by corks pierced to 

 receive copper wires. In the tubes were placed various powders, 

 bronze powder being chiefly used in preference to others, which 

 being lighter adhered to the sides of the tube. One wire was 

 thence innected with the positive conductor of an electric machine; 

 from the other the repelled electricity dissipated itself into the 

 air. In other cases the discharges of Leyden jars were employed. 

 The experiments were all conducted at atmospheric pressure. 

 When thus treated the bronze powder arranged itself in beauti- 

 fully-marked ridges or strata, varying in regularity according to 

 the original distribution of the powder. A space free from all 

 traces of powder was observed to surround the positive pole. 

 Uu^ually there was a corresponding accumulation about the 

 negative pole. These ridges or striations may be compared to 

 the stratifications observable in Geisslertubes ; and llerr Zoch 

 shows that vari.-tions in the strength of the electric discharges, 

 in the width of the tubes, &c., produce upon these figures similar 

 effects to those they produce on the luminous striaa of vacuous 

 tubes. In this present ca-e a mechanical repulsion of the particles 

 lying near the poles undoubtedly takes place ; and the author of 

 this research believes that the presence of light at the poles of 

 the Geissler tube may be similarly accounted for on the hypo- 

 thesis that the luminous regions are those of less density than the 

 non luminous. Since the bronze powder is heaped up mostly 

 about the negative pole the inference is that at the negative pole 

 of a Geissler tube the residual gas has a greater density than at 



