Ch. X] CLEANING SLIDES AND COVER-GLASSES 315 



Alcohol of 50% to 82% is also excellent for cleaning new slides, 

 and for slides which have been freed from mounting media by boil- 

 ing (§ 489) after a thorough rinsing in clean water. 



§ 488a. Absorbent gauze and lintless towels. — The gauze mentioned is 

 No. 10, " Sterilized absorbent gauze" of the Griswoldville Mfg. Co. of New York. 

 It is sometimes called bleached cheese cloth. In the author's laboratory it is cut 

 into pieces, \, £, x 1 ^ of a yard. When a piece is soiled it is thrown away. There 

 has recently appeared specially prepared towels for wiping glass etc., which are 

 called " lintless," as practically no lint is left on the wiped object. These are fur- 

 nished by Johnson & Johnson of New York, and cost about 1 5 cents each in a size 

 42 X 90 cm. 



§ 489. Cleaning used slides. — If only watery substances or gly- 

 cerin or glycerin jelly have been used one may soak the slides over- 

 night in ammonia water, then change the water for fresh and wipe 

 as described in § 488. 



When balsam or other resinous media (§ 543) have been used it is 

 best to heat the slides over a Bunsen flame and remove the cover- 

 glass. Place the covers in cleaning mixture (§ 497). The slide may 

 also be placed in cleaning mixture or in some hot water containing 

 10% gold dust or other strong alkaline cleaner. When the metal 

 basin — preferably an agateware basin — is two-thirds full of the 

 slides, heat until the water comes to a boil. Then let it cool. Add 

 fresh water and most of the slides may be wiped clean. 



If dichromate cleaning mixture is used the best method is to have 

 a museum jar of it and drop the slides in as they are rejected, or a 

 large number at once, as is most convenient. It may require a week 

 or more to clean the slides with cleaning mixture. As this is a very 

 corrosive mixture for metals use only glass dishes in dipping into 

 it. When the slides are freed from balsam, etc., pour off the clean- 

 ing mixture into another glass vessel and allow a stream of water to 

 flow over the slides until all the cleaning mixture has been washed 

 away. Then add distilled water and wipe the slides from that. Any 

 slides still not freed from the balsam should be put back into the 

 cleaning mixture. Apparently the slides are not injured by a pro- 

 longed stay in the mixture. 



§ 490. Cleaning slides for special uses. — In making blood films, 

 for micro-chemistry and whenever an even film is desired every particle 



