Notes ON. SCIENTIFIC RESEARCH. 97 
ita is only sero siniater as the author himself admits. “Warning must be given against 
a conclusion which the author draws, and which has appeared in the summary of 
_ Durrans). Moreover, this formula is only a shortened form of von Bose’s?). From the 
application of the formula to various substances, it appears that the object of steam- 
distillation in getting as much of the substance of higher boiling point than water as 
possible. into the distillate, will be the better realised the higher the temperature, and 
\ 
hence the pressure chosen. In reality the temperature if of 100° is not the boundary 
which ‘separates the substances in this respect, but their chemical nature conditions 
_ inerease or decrease of the concentration as is explained in the work of v. Rechenberg’). 
The important subject of standardisation, for long employed in mass production as 
-a time- and energy-saving device, has recently been taken up with regard to laboratory 
apparatus and has led to a first report of the Standardisation Committee of the Society 
for Laboratory Apparatus‘). Up to now, one had been advised to procure a greater 
supply of apparatus —of a certain flask, for example —if one laid value on a fitting 
substitute, but in future this will be unnecessary, because exactly dimensioned articles 
of daily use in the laboratory will be on sale throughout the whole of Germany. In 
connection with this standardisation come comparative investigations for deciding the 
effectiveness of glass apparatus, e. g., condensers and fractionating columns, as they 
. 
are taken up in a manner worthy of thanks by F. Friedrichs®), in a series of works in 
Germany and by others in foreign countries. Here Friedrichs clears away many a 
prejudice, and proves experimentally, ¢. g., with regard to fractionating columns, that 
the old Hempel column (a tube filled with glass marbles) still approaches nearest of all 
to the theoretical efficacy, whilst the numerous other constructions either do not possess 
- in the slightest degree the qualities ascribed to them by their inventors, or are far 
behind the Hempel _ column in, efficacy, which column only has one disadvantage— 
with small quantities of substance it retains too much of it. In this respect a successful 
improvement by Dufton®) appears to be appropriate. His fractionating column is such 
S that the cylindrical space between two glass tubes is provided with a wire spiral, along 
g which the condensed substance flows down, and the vapours ascend in constant contact 
with it. Indeed the cross-section and hence the efficiency appears lessened in comparison 
with the external circumference of the apparatus, so that, as it is, it cannot be recommended 
for larger quantities. At the same time the quantity of liquid retained by the column is 
reduced to a minimum. The author points out that the column works excellently with 
small quantities (10 cc.).. The apparatus has only the disadvantage that in its construction, 
a metal wire is used, which may be attacked chemically. Here the application of the 
principle of the glass Spirals introduced by F. Friedrichs might be appropriate. : 
A fractionating column, proposed by F. Friedrichs?) by reason of the results of 
a his investigations with various constructions, in which the principle of the constant 
condensing temperature as stated by Hahn‘) is applied, is indeed just as efficient as 
the Hempel column, but is excelled by this in the simplicity of its manipulation. 
—. oO Tr ee 
~ . 73 \ 
. be at Wid 
i} 
Another new fractionating column is due to M. H. Robert®). The lower part consists 
of a glass tube with constrictions filled with small glass rings of the Raschig system, 
(without stating the name of the inventor!) in a sealed-on, evacuated glass jacket. The 
middle part is a ten-bulb-tube in a glass jacket, through which a stream of air may 
~ 
1) Zeitschr. f. physik. Chem. 80 (1907), 944,. — 2) See above. — %) P.354. — 4) Zeitschr. f. ange. 
_ Chem. 33 (1920), 1. 105. — 5) Ihidem 32 (1919), I. 340; 38 (1920), I. 29. — 8%) Journ. Soc. chem. Industry 38 
(1919), T.45. — 7) Zeitschr. f. angew. Chem. 32 (1919), 1, 340. — 4%) Berl. Berichte 43 (1910), 419. — *) Compt. 
rend. 168 (1919), 999. 
7 : v 7 
