142 Scientific Intelligence. 



the region E26F— E45F, the absorption-constant for ainmonium- 

 cupric sulphate is #=0-02192 and for potassium chromate 

 /3=0-1292; and in the region E63F-E80F it is r =o-o:}47-_> lor 

 the former, and ()=0-05937 for the latter. From the formula 

 f,=--+4 the value of £ =0-52611 for the former region, and 



£ 2 = [-^=0-44003 for the latter. But when the two solu 



tions are mixed, the extinetiomcoefficient £ = 0-21468 and £ 2 = 

 0-07573. These values differ so much from the others as to jus 

 tit'v the conclusion that a chemical action of some kind has taken 

 place. If solution-- of potassium chromate and dichromate, or o1 

 permanganate and dichromate are mixed, the spectrum of tlu 

 mixture is identical with tlial of the sum of the single spectra, 

 Hence the author concludes that spectrum analysis gives a con- 

 venient, raj. id and certain method of determiningVhether in solu- 

 tions containing two or more coloring matters these substances 

 act chemically on one another or may be mixed together without 

 any chemical change taking place. — Ber. JBerl. Chem. Ges., xv. 

 1243, June, 1882. g. f. b. 



2. On the Vapor-density of Bromine. — Jahn has determined 

 in Ludwig's laboratory the vapor-density of bromine. The mate- 

 rial was carefully purified, and had a constant boiling point ol 

 63-07° C. The vapor-density was determined by Bunsen's 

 method somewhat modified. The first series of determinations 



was made at 102-6° C, and gave (a) 5'7225, (b) 5'7388, (c)5"7228; 

 mean. r>-72s. The second series, at 131-92° C. gave (<t) 5-<>:C>, (/>) 

 5*646, (c) 5-638; mean, 5-640. The third gave at 175-58° C, (a) 

 .V»;o:;, lb) .Viiii.-,; mean. .VfiOl. The foiir1*h, at 21<>-32° C, sravo 

 (a) 5-543, (b) 5-549; mean, 5'546. The fifth, at 227'92° C, (a) 

 5-5241, (b) 5-5245. (,•) 5-5244; mean, 5-5243. Taking Stas's 

 value for the atomic weight 79-951, the calculated vapor-density 

 is ———=5-5247 ; a value practically identical with that last 

 given. If further the expansion be assumed to increase with the 

 temperature ami in the linear formula \)="-\-bf. the value of the 

 constants a and b be calculated from the above data by the 

 method of least squares, a is found to be 5'8691 and £= 

 — 0-00153, Substituting in the formula, the calculated values 



being not far above the bulling point! (\ing,"i herefore, the 

 quadratic formula Ds=5-5189— gjlgg_|_ 31 90-04 ^ calcu p lU , (] va i. 

 ues come out 5-720 at 102-6° and 5-638 at 131-92°. Beyond this 

 point the linear equation holds. Calculating now the vapor-den- 

 sity of bromine at temperature- exceeding it- boiling point by 



