REVIEWS. '
(;e11
(dT ~ ~ c , (7 l tc r l I771 I: m tI O~ ~ < ~ ~ i l ( rirs. I)t
Thermodynamic Properties of Air. Part 11, Specific Heat. - 4 . IT/. II/ifX.o;,#sX.i, Phil. .l/a>. the addition of carbon, aiid with carbon in excess the carlid CTu, is formed. ./. E. T. 123,
Action of Zinc upon Photographic Plates. K : CO~SOJC. COI@frs iwidzts, 123, 49 ( 1 8 y h ) . If a fresh surface of zinc is placed in contact with a gelatine film or is separated from it only by a laj.er of some porous material, the vapor of the zinc attacks the silver bromide so that the developed plate shows a n image of the piece of zinc. Magnesium ant1 cadniiuni give the same effect ; but lead, tin, copper, iron aiid aluminum do not. I t is probable that with longer expostire the same result can be obtained with these latter inetals. 1K D . 6. Qtian fitafivc Eq~~ill'brinnz.
ilelting Points of Aluminum, Silver, Gold, Copper and Platinum. Holman, Lnwrriire, a i d Barr. The Technological Quarterly. Phil. Nag. (5) 42,37 (1896). Assiiniing 1072' C. a5 the nieltiiig point of' pure gold the authors find the following nieltiiig points by a thernio-electric method : aluminum 660', silver 970°, copper 1095' aiid platinuni I 760'. Samples of copper from different sources had so nearly identical nielting points that this temperature is reconimended as one of the fixed points in calibrating thermopiles. 117.
n.R.
Relations between the Laws of Active nasses and of Osmotic Pressure. .4. .i. Jtrko;,'ki~. %(.if. fi/(.i~s.Chtziic. 2 2 , ;rt ( 1 8 9 6 ) . From the two assuniptiotis (i.) that iii aqiieous solution a 1i)drate of the substance dissolved ( A ) is fornied accorcling to the eqnatioii A + H,O=A.H,O, and (ii) that the conceiitratioii of H1O molecules in the solution atid in pure water respectively are proportional to the vapor tension of tlie solution atid of ivater at the same temperature [suggested indirectly by Henry's law], the author deduces the ((vapor tensioti laws ) ) for dilute solutious in the form fi--&'-!l
p
I+x.71
T h i s result is directly dependent on the formula of the lijdrate, iii:.. A,H,O-froni A;H,O quite a different relation would have been obtained-iio reason however is given w h y one forniula should be chosen rather than another. 'I'he equatioii for the vapor tension o1ic.e obtained, those for the osmotic pressure, gas la\vs i i i solution aiid H e n r y ' s law follow without difficulty : the deduction of tlie ( ( indexed H e n r y ' s law ) ) on the other hatid is not at all clear. T h e author's results cannot 1iower.er lie considered as justifj.ing his premises. as they may be arrived a t by niethods free froill special li!potheses as to tlie nature of solution : the vapor tension law in particular can be deduced b ~ rpurelj. tlierinotlyiian~icconsiderations from the gas laws and tlie law of Heiiry alone, and consequently the introduction (in addition to these) of the h j d r a t e lijyotliesis is wholly unnecessary. 1'. .!I.
Freezing-point Depressions of very Dilute Solutions. R. .-/hk , Zcit. ~,~ p h~- ~ , .C~h. ( m . 20, 207 (, rS94 ) . T h e apparatus of Nernst aiitl Abegg is improved by using ice aiitl a dilute salt solution in the freezing bath ; bj, shielding this latter 011 all sides with felt and ~ 0 0 ;1 and by having autoniatic stirrers, with vertical iiistead of rotary iiiotion, in the bath and in the solutioii. A liter of solutio11 is used. T h e therriioineter is tlii.ided into 1 i 5 0 o O aiitl has aii electric hatiliner attached. Soiiie satisfactory iiieasurements were made wit11 various non-electrolytes and salts : but potassium iiitrate arid magnesiuni sulfate were not examined. Equilibrium is reached \Frit11 potassium chlorid in half the titile necessary with cane sugar. 111. D. 6.
On the Solubility of Barium. Sulfate. F. If7. /i;;)stc,i-. &it. niiorg.. Chriti. 12, 261 (1896). T h e author olijects to such a phrase as ( ( Solubility in the nascent state ) ) . H e shows that Fresenius and Hintz have nieasured the concentration of a super-saturated solution and that the true solubility of barium sulfate is roughl). one part in 425,000, as was found by Kohlrauscli and Rose and by Holleman. T h e author also shows that most of the peculiarities found by Fresenius and Hintz can he predicted from Nernst’s theor), of solubility. A yery interesting point conies out in this paper : that barium sulfate forms a solid solution with sulfuric acid. kif. D. /i.
On a Compensation-Method in Gasometry.
c-.
T1 h t r ~ . &it. flhjts. rheu?. 20, 307 ( 1 8 9 6 ) . T h e principle 011 which the method rests is that the ratio between the ‘volunie of the gas at a given temperature and pressure and the voluine of the gas at nornial temperature and pressure is independent of tlie nature of the gas. By comparing the actual \.olunie of the gas to be attal!~zed wit11 the actual volume under the sanie conditions of another gas, the noriiial volunie of which has been determined once for all, one has all the data necessary. T h e advantage of this method is that neither pressure nor temperature needs to be known. It is merely necessary that the pressure and temperature of the gas in the eudiometer shall he the same as that in the standard tube. When the gas to be analyzed is moist, a little water must he introduced into the standard tube. r,v. D. R. 7
~
Thermochemical Data for Mercuric Cyanid. K . I ’OW/. .41tu, chtinc. #/zjv. ( 7 ) 8 , 437 ( [ 8 9 6 ) . A tabulated summary of the heat effects produced by the action of the halogen salts of tlie alkali metals and the alkaline earths upon mercuric cyanid. IV. D. 6.
. A General Verification of the Corresponding States of van der Waals, E. H . .4iiingnt. Coiii/&.s endu us, 123, 30 ( r 8 9 6 ) . ( ( T h elam of corresponding states can be put in the broadest way thus : If groups of isotherms of any two substances are drawn to the same scale, pressures and volumes being expressed in terms of their critical values, the groups of isotherms should be capable of
Rmirws.
67
being superposed producing a single group of isotherms belonging apparently to onl!. one substance.)) Therefore, it should always be possible to make a group of' isotherins of one substance coincide with a group of isotherins of another substance on readjusting tlie units used in drawing tlie isotherms, by expanding or contracting tlie axes of coordinates. T h i s was done by optical projection for the isotherms of carbon dioxid, ether, and air, in one case and for tlie isotherms of ether aiicl ethylene in another case. T h e coincidence was excellent and full). supported the theory of \.ail der Waals in these tivo cases. Unfortuiiatel!., such a test could not be made with other bodies for lack of data. C/irJ.eJI(.P Id. sfi
