282 



NATURE 



\yan. 25, 1877 



It is stated that Calandrelli published an account of his obser- 

 vations in the Roman journals in December, which was transferred 

 to the official journal of Palermo on the nth of the same month. 

 Perhaps a reference to the Italian journals might bring to light a 

 further observation or observations ; the comet is said to have 

 been bright, but the weather about the date of discovery was 

 unsettled, and for several days previously had prevented observa- 

 tions of any kind. 



Coloured Belts on Jupiter. — In connection with the 

 supposed periodicity in the appearance of marked colour on the 

 belts of this planet, the observations of Gruithuisen, of Munich, 

 in the years 1836-40 possess interest. They are found in his 

 Astronomische Jahrbuch, 1839, p. 76, 1840, p. 99, and 1841, 

 p. loi. He first noticed the colour on April 23, 1836, at 9sh., 

 when, observing with a 30-inch refractor of 2$ inches aperture, 

 and power 150, the single central belt then visible had a brown 

 tint throughout, and he states that, hardly believing his own 

 vision, he called a person who was at hand, and on asking him 

 what colour the belts presented, he replied ' ' the colour of rust." 

 With a 5-feet telescope, powei 120, the brown tint was not dis- 

 tinguished. On subsequent occasions he found that with the 

 highest powers of the telescope the belt appeared of a bright 

 reddish brown, while with the lower powers it was merely of a 

 dark shade, and hence concluded that the intensity of light was 

 disadvantageous to discerning the colour. In addition to the 

 brown tint of the central belt, it was remarked that the planet 

 near its north pole had a bluish-grey tint in May, 1836 ; a few 

 months later Dr. Albert, a pupil of Bessel, observing with a 

 30-inch telescope, found the polar region "quite blue." The 

 length of Gruithuisen's descriptive remarks prevents their being 

 transferred to this column, but we refer to the observations, as 

 his annual volumes are not often met with here, and the fact of 

 such observations having been made forty years since may not be 

 generally known. That these tints should have been conspicuous 

 with such small optical aid is worthy of note. 



The Intra-Mercurial Planet.— In M. Leverrier's last 

 communication to the Paris Academy on the planet assumed to 

 exist within the orbit of Mercury, it was mentioned that, with 

 the elements adopted, or very similar ones, a solar conjunction 

 would occur on March 22, and a transit over the sun's disc was 

 possible, though uncertain. A close examination of the disc is 

 therefore to be recommended on March 22 and 23, and there is 

 reason to believe that observers in widely-differing longitudes 

 are prepared to undertake it. If no transit should then occur, 

 eight or nine years may elapse before one is possible at the 

 spring node. 



CHEMICAL NOTES 



Atomic Weights of Caesium and Rubidium. — M. 

 Godeffroy gives an account in Liebig's Annalen of some deter- 

 minations he has made on the above subject. To obtain pure 

 material he employs Redtenbacher's method for the separation 

 of the caesium, rubidium, and potassium, by preparing their 

 respective alums, separating these by fractional crystallisation, 

 and finally converting them into pure chlorides of the metals. 

 The determination of chlorine in the non-diliquescent caesium 

 chloride, gave, as the mean of four closely-agreeing experiments, 

 the atomic weight of caesium as equal to 132*557, the atomic 

 weights of chlorine and silver being taken as 35 '46 and 107 -94 

 respectively; from analogous experiments the author finds the 

 atomic weight of rubidium to be equal to 85 '476. 



On the Specific Heat of Gases. — In Poggendorff's 

 A nnaHen, clvii., E. Wiedemann gives |a most interesting com- 

 munication on this matter, in which he criticises the experiments 

 of Regnault on the same subject, and describes a new method of 



determining the specific heats of gases introduced by himself. 

 On comparing the author's results with those of Regnault it is 

 found that the method employed by the former is not inferior in 

 accuracy to that of Regnault, and also that a great economy of 

 material may be effected by using Wiedemann's process ; this 

 economy giving the experiments greater range in a comparatively 

 shorter time. The following tables give a synopsis of the num- 

 bers and numerous tables given in Wiedemann's paper : — 

 Specific Heats of Equal Weights. 



Air 



Hydrogen 

 Carbon monoxide 

 Carbon dioxide 



Ethylene 



Nitrous oxide . . . 

 Ammonia 



0-2389 

 3-410 

 02426 

 0-1952 



0-3364 

 0-1983 

 0-5009 



IV. 



o 

 o 

 o 



22-28 

 49 08 



23*15 

 12-38 



Specific Heats of Equal Volumes. 



Air 



Hydrogen 



Carbon monoxide... 

 Carbon dioxide ... 



Ethylene 



Nitrous oxide 

 Ammonia 



Specific 

 weight. 



I 

 0-0692 

 0-967 

 1-529 

 0-9677 

 I -5241 

 0-5894 



IX. 



P V 



P'V 



I -00215 



I -00293 

 I -00722 



I -0065 1 



I-OI88I 



Columns I., II., III., contain the true specific heats at the 

 temperatures indicated ; column IV. the difference of specific 

 heat at 0° and 200° expressed in percentage of the specific heat at 

 0°. Columns V., VI., VII., represent the true specific heats in 

 reference to the unit of volume, the specific heat of the unit 

 volume of air being taken as 0-2389; column IX. gives 

 Regnault's proportions of the products of the volumes V and V, 

 and the pressures P and P', when P is at the pressure of one, and 

 P' at the pressure of two atmospheres. Herr Wiedemann thinks 

 that the specific heat determined in these experiments seems to 

 be composed of two parts, the heat caused by work expended on 

 the expansion of the gases in overcoming outside pressure, and 

 secondly, the heat employed in the internal work of the gas 

 itself. He also thinks that attempts to determine the separate 

 parts of the heat of molecular motion, of which the specific heat 

 is composed in constant volumes — of the heat of atoms according 

 to Naumann— and also the attempt to establish simple relations 

 between the two to be still premature, as the alteration of the 

 specific heat with the temperature would cause these effects to 

 have different relations between different temperatures. The 

 author thinks that the alteration of specific heat of the gases with 

 the temperature cannot be explained by the deviation of such 

 gases from the perfect gaseous condition. As an illustration of 

 this he cites the case of ammonia gas, which, although more 

 remote from the state of a perfect gas than nitrous oxide or 

 carbon dioxide, still possesses smaller variations of its specific 

 heat with change of temperature than either of these latter gases. 



Action of Antimony Pentachloridk on certain Or- 

 ganic Substances. — The action of this re-agent on some 

 organic substances has lately been investigated by C. W. Lossner, 

 who gives an account in the fourn. pour Chimie of the results he 

 obtained. When chloroform and antimony pentachloride are 

 gently heated together, preferably in sealed tubes to 100° C, the 

 chloroform becomes converted into carbon tetrachloride. Ethylc 



