( 628 ) 



o' - o - II - 2 5 — 2 w = 3 (r + (9), 



then 



;. = 2 r 4 2 ^ — 2. 



So the (Mii'xo C iiieels the cone K outside P still 2 r — 2 times, 

 rimI /' comil.^ lol' Iwo points of intei-seeti<»n. So the curve i! also 

 meets the conic c. \\'\\\% on A' only Uvo limes and consequently 

 the cui-\e (/, haviii^i' with (\ li\e points iu common at P, meets it 

 also oid\ two times. 



Chemistry. — "yl contrihution to llw hio>rIt'(h/t' of the course of 

 the (lecrease of the vapour tension, for aqueous sohitinns." 

 Bv Dr. A. Smits (Communicated by Prof. H. W. Bakhuis 



IvOOZEBOOM.) 



1. Ill I7SS Bi.AGDEN^) discovered the relation between tlie lowerinp; 

 of the i'lVQ/AW^ point and the quantity of the solved substance. 

 Amon^- the substances which he examined, wei-e however also some, 

 which showed deviations, either in this sense that the lowerinii- of 

 tlio frec/.iii.U' ]ioinl increased nioi-e ra|)idly or in tliat sense that it 

 increased more slowly than the concentration. 



UtDOKFF-), who quite i,unorant of Bt.agdkn's work, made the 

 same discovery in 1861, and ('oppht''), ^vho ten years later (187J), 

 coniiiiiKMl PvUDOkff's investig-ations, came both to the result, that 

 de\iations trom the rule first discovered by Blaodkn, occurred both 

 in one sense and in the othei'. A dispro|)Oi-tionately rapid increase 

 of the lowerinp: of the freezing ])oint with the concentration was 

 found aiiiong others for NaFJr, NaJ. CaCL H.^SO, and also for NaCl, 

 whereas for the nitrates of Xa, NH^, Ba, ('a, Sr, Pb, Ag and for 

 Xa^SO,, Na/X)^, XH.CXS the reverse was observed. 



As an illustration of the course, as for NaBr etc. RüDOin'i- had 

 already adopted the formation of hydrates, ('oppet assumed foi' the 

 deviations for the nitrates, which are mostly anhydrous, that they 

 are modified by the action of water or 1»\ the fall of the tempera- 

 ture ill a ccrlaiii, not further delined way. 



Results analogous to those of Blagden, Rüdorfk and Coppet were 

 obtained by Tammann ^) in 1887 when determining the decrease of 

 the vapour tension. Tammann found namely, that for most of the salt 



1) Wied. Ann. 39, 1. (iS'JOj. 



2) Pogg. 114, iVS. Cl<S(Jl); ib. 116, 05 (1802); ib. 145, 509 (1871). 



•') Ann. Cliim. F^hys. (4) 23, 366. (1871); ib. 25, 502. (1872} ; ib. 26, 08 (1872). 

 ') Wied. Ann. 24, 523. (1885). 



