APPENDIX. 



927. Chemicals, Stains, and Apparatus. Addresses from which 

 it is recommended that these be obtained are given in 11. 



928. Cleaning Slides and Covers. New ones should first be 

 soaked in one of the following liquids : strong sulphuric, 

 hydrochloric or nitric acid, or aqua regia, or a mixture of an 

 ounce each of sulphuric acid and bichromate of potash with 

 from 8 to 12 ounces of water, then washed first with water 

 and lastly with alcohol, and dried with a clean cloth. 



For used ones, if a balsam mount, warm, push the cover 

 into a vessel with x} lol or other solvent of the mount, and 

 put the slide into another vessel with the same, leave for a 

 few days, and then put into strong alcohol. If this is not 

 sufficient, treat as for new ones. Some persons boil in lysol, 

 which I do not find efficacious. 



For the final treatment, see p. 121. 



929. Gum for Labels. Labels stuck on glass often strip off. 

 This may be avoided (MARPMANN, Zeit. Anyew. Mik. 3 ii, 1896, 

 p. 151 ; Journ. Roy. Mic. Soc., 1897, p. 84) by means of the 

 following adhesive : 120 grammes of gum arabic are dissolved 

 in a quarter of a litre of water, and 30 grammes of gum tra- 

 gacanth in a similar quantity. After a few hours the tra- 

 gacanth solution is shaken until it froths, and mixed with 

 the gum arabic solution. Strain through linen and add 150 

 grammes of glycerin previously mixed with 2 grammes of 

 oil of thyme. 



PEIRCE (Journ. app. Mic., ii, 1899, p. 627 ; Journ. Roy. Mic. 

 8oc., 1900, p. 404) finds that if the end of the slide be 

 painted with a thin solution of balsam, it may be written on 

 with ink when dry, and the record preserved by a second 

 coat painted over it. 



For other receipts see early editions. 



