April 13, 1882 | 
two cases of recent occurrence. The fifih comet of 1877 was 
detected by Tempel on October 2, when its south declination 
was already 10°, and its motion towards the south did not permit 
of its being followed after October 14, when the last observa- 
tions were made at Leipsic and Milan. On the orbit being cal- 
culated, it was found that the comet had passed the perihelion 
as early as the end of June, and, further, that it had escaped 
observation before perihelion, when in a much more favourable 
position than at the time of its discovery by Tempel. Thus, on 
April 5, as the moon was drawing away from the evening sky, 
it was in R.A. 161°, Decl. +57°, consequently a circumpolar 
object in these latitudes, its distance from the sun was 1°69, and 
from the earth 1°05, and the intensity of light, expressed in the 
usual manner, was 0°32, At its actual discovery, on October 2, 
the distance from the sun was 1°86, and from the earth 0°88, 
consequently the intensity of light was 0°36, or virtually the 
same as on April 5. But the orbital arc available for the final 
calculation of the elements was less than 43°, whereas if the 
comet had been detected in its more favourable position towards 
the end of the first week in April, there would have been avail- 
able for this purpose an orbital arc of upwards of 160°. 
As a second case in point, we may mention the circumstances 
attending the discovery of the comet by Mr. Denning last Octo- 
ber, and its previous track, Mr. Denning found it on October 
3, the perihelion passage having taken place on September 13, 
so that it was already at a considerable angular distance from 
perihelion at the first accurate observation. But prior to arriv- 
ing at its least distance it had made the following tour of the 
southern heavens. In the column headed “ Intensity of Light,” 
the brightness at discovery on October 3 is taken as unity. 
zh. G.M.T. Roa es Terence om ee of 
June 26 ZOOM nes eb = 3S" 07481 o's 
July «25 280°3 66'9 O°159 II'9 
30 228°5 80°5 o'128 20°4 
PANIC 2) in, 58:9 74°9 ors 25°6 
Goa sc. a 1A 302 65'°6 o'li6 27°6 
Ge, 13670 55°6 O'lIg 27°9 
SS) Becee LGRGES —45'8 O25 e 2055 
Sepeirg) =-. 129°2 +11 0'503 ... 2°9 
With anything approaching to a regular examination of the 
southern sky such an object could not have escaped notice. 
CHEMICAL NOTES 
WHETHER the atou ic weight of uranium is represented by the 
number 120 or 240, is still a disputed question. Experiments 
recently conducted by Herr Zimmermann (Zerich/e) are strongly 
in favour of the latter number. Herr Zimmermann has deter- 
mined the densities of the va, ours of uranium tetrabromide and 
tetrachloride, by Victor Meyer’s method, at the temperature of 
a Perrot’s furnace ; his results are as follows :— 
Sp. gr. of vapour. Calculated. 
Se Neo 
U=120. U=240. 
Uranium tetrabromide . 19°46 (mean of 6) ... 9°68 19°36 
Uranium tetrachloride... 13°33 (mean of 4) ... 660 13°21 
SEVERAL important papers on general considerations regarding 
processes of chemical change, by MM. Potilitzin, Beketow, and 
Kajander, have appeared in the Youwrzal of the Russian Chemical 
Society (good abstracts in Berliner Berichte, xiv, 2044-2058). 
As a deduction from experimental results, M. Potilitzin con- 
cludes that in every reaction, whether in presence or absence of 
water, a division of the elements of the reacting bodies occurs, 
and this is conditioned by the atomic weights of the elements, 
and the mass of the reacting substances. SBerthelot’s principle 
of maximum work is only applicable when but a single product 
is formed in a reaction, and when the energy, liberated in the 
reaction, all appears as heat. But in actually-occurring processes 
of chemical change there is a conversion of potential into kinetic 
energy, and subsequent employment of this kinetic energy in the 
work of fusion, evaporation, affinity, &c. Sometimes a portion 
of this energy may be used in the formation of compounds 
wherein heat is absorbed. This change of potential into kinetic 
energy is counterbalanced by the conversion of energy of motion 
into heat: a condition of equilibrium for the entire chemical 
system is thus attained, conditioned chiefly by the atomic 
weights of the reacting elements, the masses of the chemical 
substances in the system, and the relative amounts of potential 
and kinetic energy. The heat evolved in a chemical change | 
NALORE 
567 
measures the initial velocity of that change; but the final result 
of the change is dependent on the attainment of a general 
equilibrium, the conditions of which have been stated. Any 
change in one or more of these conditions causes a change in 
the direction of the chemical reaction. 
In the paper of M, Kajander the action of acids on plates of 
magnesium Is considered ; it is shown that the velocity of the 
action is inversely proportional to the internal friction of the 
liquid : raising the temperature of the liquid acts by diminishing 
the internal friction. 
PROF. MENSCHUTKIN continues to publish, in the ¥ournal of 
the Russian Chemical and Physical Society his researches on the 
influence of isomerism on the formation of compound ethers, 
and deals with the etherification of polybasic acids. The re- 
searches are rendered difficult by the circumstance that we know 
but few polybasic acids, the structure of which is well deter- 
mined, Altogether the etherification of polybasic acids is very 
like the etherification of monobasic acids ; the limits of etherifi 
cation are always high, if a primary alcohol is taken for the for- 
mation of the ether; the rate of etherification varies with the 
isomeri-m of the acid, and the variations of the rate are as in 
monobasic acids. This likeness is the more remarkable, as the 
reactions are far more complicated in this case than in the 
preceding one. 
Pror. MENSCHUTKIN also discusses the influence of the 
molecular weight of homologues on the course followed by in- 
complete and reversed reactions. He has succeeded in establishing 
that the law of homology, extends as well to the chemical as to 
the physical properties of homologues, and as well to their 
complete reactions, as to the incomplete ones. 
THE phenomenon noticed by Mills, and called by him 
“chemical repulsion”—referred to some time ago in these 
“Notes ’’—has been recently studied by Herr Lecher (Wien. 
Akad, Ber.), who thinks that there is no need for the new 
hypothesis of chemical action at a distance introduced by Mills. 
A few drops of barium chloride solution are placed on the sur- 
face of a glass plate, a second plate containing two circular holes 
is pressed on the first, and a drop of sulphuric acid is introduced 
at each hole: the formation of barium sulphate proceeds in 
circles which gradually extend their circumference, but cease to 
do so before they come into contact. The author’s explanation, 
which is based on several experiments, assumes that the barium 
chloride molecules originally move equally in all directions 
through the liquid; the presence of sulphuric acid, however, 
fixes many of these molecules and prevents their moving out of 
the sphere of action of the acid: the space between the advan- 
cing circles of barium sulphate thus becomes gradually poorer 
in barium chloride, until finally the whole of this salt is 
removed : there is a space of no action, because the compounds 
which react are absent. 
HERR SCHULZE (Journ. fiir pract. Chem.) describes an 
interesting case of so-called ‘‘catalytic action.” . Sulphuryl 
chloride (SO,Cl,) is not formed by the action of chlorine on 
gaseous or liquid sulphur dioxide, but if these gases be passed 
over camphor, large quantities of sulphuryl chloride are pro- 
duced ; five grams of camphor sufficed to induce the formation 
of 470 grams of sulphuryl chloride. Acetic or formic acid likewise 
induces the combination of chlorine and sulphur dioxide, but these 
compounds are themselves more or less attacked, whilst camphor 
remains unchanged at the close of the reaction. Acetic and 
formic acids dissolve considerable quantities of sulphur dioxide, 
but other good solvents of this compound, e.g. acetone, fail to 
induce the formation of sulphuryl chloride. 
MALLET (Amer. Chem. Fourn.) finds the number 1°759 as 
representing the sp. gr. of hydrofluoric acid gas at 25°, hence 
molecular weight = 39°32. If this determination is confirmed, 
the formula of the compound in question must be written H,F, 
and not, as at present, HF, But if Mallet’s formula is correct, 
the atom of fluorine must be divalent; it has hitherto been 
regarded as markedly monovalent. 
M. L. DE BOISBAUDRAN (Compt. rend.) has prepared gallic 
chloride, Ga,Cl,. The specific gravity of the vapour of this 
chloride, at 273°, was found to be 11°9, which confirms the 
formula Ga,Cl,. 
AN iron wire embedded in lampblack and heated to redness 
in the reducing flame of the blowpipe loses weight ; a portion of 
the iron, according to Colson, diffuses into the carbon. This 
chemist states that solids diffuse into each other when a chemical 
