272 
The Ohio Naturalist. 
[Vol. V, No. 3, 
HYDROFLUORIC ACID FOR MARKING SLIDES. 
Joseph F. Clevenger. 
Various methods have been described for labeling slides in a 
series, or for keeping track of them while staining. The principle 
of etching glass with hydrofluoric acid has been known for a long 
time, and use has been made of it in various ways, but it does 
not seem to have been employed to any extent by biologist for 
marking slides. 
The writer has tried a number of methods recently published 
for marking slides, but for one reason or another they were not 
very satisfactory. Generally the mark became so obliterated in 
passing through the stains and grades of alcohol that they were 
beyond recognition. 
Through a suggestion offered by ]\Iiss Lumina C. Riddle it 
occurred to me that hydrofluoric acid might be suitable for this 
purpose. Very satisfactory results were obtained by the fol- 
lowing method: 
Take a thoroughly cleaned slide dip one end into paraffin and 
let it cool. Take a needle and make whatever mark is desired, 
and then with a toothpick, or a similar piece of wood, apply a 
drop of hydrofluoric acid to the mark. Let this remain from two 
to five minutes; then melt the paraffin and clean the slide. Any 
number of slides may be marked at a time and the method is 
nearlv as rapid as that with ink and much more reliable Ordi- 
narv precautions must be taken in handling the hydrofluoric acid. 
MEETING OF THE BIOLOGICAL CLUB. 
Orton Nov. 7, 1904. 
The meeting was called to order by the president and the 
minutes of the previous meeting were read and approved. 
Mr. Sanders, the retiring president, read a paper on ‘ ‘The 
Uses of the Bacteria in the Arts ” Prof. Schaffner reported 
Kuhnistera purpurea (Vent.) MacM. for Columbus. It is a rare 
plant in Ohio. Prof. Landacre gave some observations on the 
rate of growth of Vorticella. Mr. J. C. Britton of Washington, 
D. C., gave an account of a recent trip to Bermuda. Mr. Burgess 
of the State Agricultural Department, stated that the Elm Leaf 
Beetle had been found in Dayton this autumn. 
The president appointed F. L. Landacre, J. H. Schaffner, and 
Z. P. Metcalf to act as a committee on nominations to select 
officers for the coming year. 
J. N. FR.A.NK, Sec. 
Date of Publication of January Number, January 24, I90S. 
