64 CCIOPTICON MANUAL. 



the solution by allowing a plate coated with excited col- 

 lodion to remain in it over night. Filter. 



Developing Solution. Make a saturated solution of 

 ammonia, sulphate of iron (in water); filter. To every 

 ounce of this solution add glacial acetic acid, 1 drachm. 

 This can be used as a stock solution, and will keep an 

 indefinite length of time in good condition. Crystals 

 will form in the stock-bottle, after standing some hours, 

 but that is of no consequence, as the strength of the 

 solution is correct. 



In developing a plate, use 5 drachms of water to 2 

 drachms of ammonio-sulphate of iron from the stock- 

 bottle. During hot weather use ice-water to retard the 

 action of the developer. 



Fixing Solution. Cyanide of potassium or hyposul- 

 phite of soda; either will answer, but the action of 

 cyanide appears to make a somewhat brighter picture. 



These solutions being carefully prepared, the picture 

 accurately focused, the negative (collodion side towards 

 the lens) covered with a dark cloth, prepare the plate 

 in the dark-room in the usual manner, place it in the 

 dark-holder, in the position of the ground-glass, draw 

 the slide (the lens is always uncovered), remove the 

 cloth from the negative for a few seconds. The expo- 

 sure will then be made. Cover the negative, shut the 

 slide, and remove to the dark-room for development. 

 The picture should appear slowly; not flash out upon 

 the first application of the iron solution. Over-expos- 

 ure, as well as over-development, are both fatal to trans- 

 parencies. No trace of fog should be visible. From 

 five to fifteen seconds will be found sufficient, on a bright 

 day, with a negative of ordinary strength, and the 

 chomicals in good order. 



The Negative Must be sharp, of good printing densi- 



