0. Seeker — Gravity Determinations at Sea. 393 



To my surprise he introduces the expression e(t — t a ), for the 

 change of the instruments depending on time, into the equa- 

 tions for the adjustment ; he even thinks that later on perhaps it 

 will be necessary to introduce a quadratic term. He thus tries 

 to find a correction for the relation between freezing-point 

 determination and barometric correction. This of course 

 influences his determination of the freezing-point. I will not 

 enter further into Bauer's plans. I leave them to the future. 



The above explanations should prove sufficiently, that I was 

 justified in characterizing the criticism, as I did at the begin- 

 ning of these pages, as carelessly made and in every way 

 mistaken. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Volumetric Determination of Iron and Vanadium. — 

 Mullee and Dieffenthaler have found that vanadic acid is 

 readily reduced to V 2 4 by the action of hydrochloric acid and 

 alcohol, while this reaction is difficult to complete by the action 

 of hydrochloric acid alone. For the analysis of ferro-vanadium 

 they dissolve 1 g. of the substance in not too much concentrated 

 nitric acid, evaporate off the excess of acid and decompose the 

 nitrates with a little concentrated hydrochloric acid. Then they 

 add 50 cc of alcohol and 20 cc of concentrated hydrochloric acid 

 and evaporate, first over the wire-gauze, with gentle boiling, then 

 on the steam-bath to about 5 CC . The residue is transferred with 

 water to a graduated flask, and an aliquot is taken for the deter- 

 mination of iron, most conveniently by the iodometric method as 

 presented by Treadwell in his text-book, while the remainder of 

 the liquid is titrated for vanadium with l/lO normal permanganate, 

 after an addition of manganese sulphate, at ordinary tempera- 

 ture. The authors state that the results are exact for vanadium 

 by this method, but that while the vanadic acid may be reduced 

 by alcohol and sulphuric acid, organic matter acting upon perman- 

 ganate is left in the solution by this means of reduction. — Zeitschr. 

 Anorg. Chem., lxxi, 243. h. l. w. 



2. The Passive State of Metals. — The fact that a group of 

 metals, especially iron, nickel and chromium, are capable of 

 assuming a passive state in which they are not attacked by cer- 

 tain acids, is very well known, and it has been the subject of 

 much speculation and investigation since the time when Faraday 

 advanced the theory that the passive state is due to the forma- 

 tion of a protective film of the oxide of the metal. Several other 



Am. Jour. Sci.— Fourth Series, Vol. XXXII, No. 191.— November, 1911. 

 29 



