results on any type of specimen. It gives a durable, pli- 
able, transparent film which will not ‘‘yellow’’ or harden 
with age. The consistency is viscous enough to minimize 
the occurrence of air bubbles. 
Parlodion (Mallinckrodt) . . . 28 grams 
Butyl Acetate (commercial) . . 250 ce. 
Amy! Aleohol ..... . . 80ce. 
Xylol (or Toluene) . . . . . 10ce. 
Castor Oil . . 2... . . Bee. 
Ether .... 3 ce. 
The solution should be allowed to stand a week be- 
fore being used. 
Parlodion is rather expensive, but the results are 
much superior to those obtained by guncottons (com- 
mercial nitrocellulose). We have compared a large series 
of nitrocellulose substances in our experiments. The 
majority showed a definite tendency to ‘yellow’? and 
‘brittle. ”’ 
Chloroform may be substituted for ether. This is 
added to hasten hardening along the edges of the film. 
Castor oil makes the film pliable. Amyl acetate can be 
used as a substitute for butyl acetate, and in this case 
no amyl alcohol is needed. 
Peeling. The solution dries slowly and will not be 
ready for removal for six or eight hours. Peels with a 
surface greater than 9 square inches will not dry in less 
than 12 hours. The surface of the specimen is ‘*‘peeled”’ 
with the film, by first loosening one edge, and then care- 
fully pulling off the whole film. We have prepared peels 
up to the size of eighty square inches, and such peels 
possess a uniform thickness and toughness. A thoroughly 
dried film will not wrinkle or curl after removal. 
Care of Peels. Some workers prefer to file the peels 
in envelopes or folders. No special care is really neces- 
sary. However, one cannot subject an unmounted peel 
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