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 Miss 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 

 nearly as rapid as that with ink and much more reliable Ordi- 

 nary precautions must be taken in handling the hydrofluoric acid. 



MEETING OF THE BIOLOGICAL CLUB. 



Orton Hall, 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. Frank, Sec. 



Date of Publication of January Number, January 24, 1905. 



