B42 REPORT—1899. 
tion bands of various dye-stuffs and colouring matters. He found the 
velocity greater the larger the number of hydrogen atoms in the molecule. 
His experiments do not appear to have been quantitative, as no propor- 
tions of a molecule of the substances taken are mentioned, nor are even 
the quantities of the substances or the thicknesses of the liquid recorded. 
The numbers recorded are given as the number of intra-molecular vibra- 
tions per billionths of a second. 
Solvent used 
CHCl, H.SO, 
FRG HO: [UT Dida IRONY RE TRB, Oe 8 CT gg grils Nae 
m. Methyl-indigo 3 ; ; : : : : . | 4825 — 
m. Oxymethyl-indigo . é ; : : : ; : 459°4 = 
Ethyl-indigo . ¢ : 3 . ; ; ~ . | 945872 — 
Brom-indigo . : : ; : E : : | 493-2 —_— 
Dibrom-indigo . ; 5 are : 3 : ; 479'9 _ 
Nitro-indigo E 5 : : : : ‘ - - 510°8 = 
Amido-indigo . ; : . é : : é : —- 507‘7 
Dibrom-amido-indigo. . : : : : 3 — 511-0 
A number of fluorescein derivatives were examined. 
Water Alcohol 
Fluorescein : F : ; 4 2 . 4 ; 612:2 
Fluorescein potassium salt A . é 5 5 . | 605°3 621°9 
Dibrom-fluorescein potassium . ie . A -| 595-1 1 oce 
Tetrabrom-fluorescein ‘ . , 6 4 : ; se { ee 
i ‘ 4 569-4 
Tetrabrom-fluorescein potassium ‘ : . “ c 579'6 { 6085 
Tetranitro-fluorescein 4 3 ; i : : y 611°5 570°8 
Tetranitro-fluorescein potassium . F . : : 611°5 597°5 
Dibromnitro-fluorescein , . . . . . : 5956 . ape 
Dibromnitro-fluorescein potassium . . . . : 595°6 583°6 
Monomethyl-tetrabrom-fluorescein , - = fs ‘ — { ie 
Monomethyl-tetrabrom-fluorescein potassium . . - { nh 
Monethy1-tetrabrom-fluorescein . ’ Bh 7s . == { ie 
Monethy!-tetrabrom-fluorescein potassium x , 4 — { als 
Potassium rosolate . = Fi 7 + . A c 5503 5251 
Potassium tetrabrom-rosolate . : 5 ‘ : 3 527°9 518°3 
In the case of analogous replacements of the hydrogen atoms, the 
increase or decrease of molecular vibrations is proportional to the number 
of hydrogen atoms thus replaced. It seems that these results are in 
accord with some deductions from experimental results obtained by 
Rellstab, ‘Inaugural Dissertation,’ Bonn, 1868, on the transpirability of 
homologous compounds, 
G. Kriiss returns to this subject and gives an account of his experi- 
ments in the ‘ Zeitschrift fiir physikalische Chemie,’ vol. ii. pp. 312-337, 
