SYNTHETIC CULTURE MEDIA. 



20I 



Orlol Develol^cr. 

 (See pp. 140-141.) 



Pyro Developer for Dry Plates. 

 (Recommended by S. G. Lofft.) 



(i) Water 10 oz., or 300 cc. 



Citric acid 10 grains, or 6.46 grams 



Pyrogallic acid... i oz., or 31 grams 



(2) Sodium sulphite 



(crystals) 4 oz., or 124 grams 



Water 16 oz., or 480 cc. 



Or 



Seed's sulphite. ...It/ oz., or 46.5 grams 



Water 16 oz., or 480 cc. 



(3) Sodium carbonate 



(crystals) 4 oz., or 124 grams 



Water 16 oz., or 480 cc. 



Or 



Seed's carbonate. 2 oz., or 62 grams 



Water 16 oz., or 480 cc. 



To develop take — 



Water 4 oz., or 120 cc. 



No. I 2 drams, or 7.5 cc. 



No. 2 V2 oz., or 15 cc. 



No. 3 J4 oz., or IS cc. 



For underexposures dilute and change fre- 

 quently to fresh developer. 



For overexposures use old developer or re- 

 strain with a few drops of 10 per cent potassium 

 bromide. 



Laiilerii-slide Developer. 



(Used in Laboratory of Plant Pathology.) 



Distilled water cc. . goo 



Carbonate of soda (cryst. ) grams.. 39 

 Sulphite of soda (cryst. ). ..c^rams. . 39 



Hydrochinon grams. . 13 



Add the hydrochinon after solution of the 

 soda salts, and put at once into a glass-stoppered 

 bottle. For use take 3 ounces of above and 3 

 ounces of distilled water, to which add 5 drops 

 of a 10 per cent solution of bromide of potas- 

 sium. If properly exposed the image should 

 appear in 30 to 60 seconds, and the development 

 should be over in 3 or 4 minutes. Good for a 

 dozen or more properly exposed slides. 

 Zetfiww's Copper-chroiii-filter. 



Dry, pure, copper nitrate 160 



Pure chromic acid 14 



Distilled water 250 



This may be diluted further with water if 

 desired. 



In case there is difficulty in preparing the 

 above, a solution, stated by Zettnow to be nearly 

 as useful, consists of — 



Sulphate of copper 175 



Bichromate of potash 17 



Water 1,000 



(Centralb. f. Bakt., IV Bd., 188S, p. 51.) 

 Neuhaus sa^-s, water 500 to 1,000, and alsi". 

 2 cubic centimeters of sulphuric acid. This so- 

 lution extinguishes all the blue and violet rays. 



Toning Bath for Solio Paper. 



(A) Hyposulphite of soda... Bounces 

 Potash alum (crystals),. 6 ounces 



Cane sugar 2 ounces 



Water 80 ounces 



Dissolve cold, then add 2 ounces of borax 

 which has been dissolved in 8 oz of hot water. 

 Let stand 12 hours, and then decant. 



(B) Piu'c chloride of gold.. 7.5 grains 



Acetate of lead 64 grains 



Distilled water Bounces 



This solution must not be filtered and must 

 be shaken thoroughly each time before using. 

 Solio paper should be printed aliout one-third 

 darker than it is desired to have the pictures. 

 When the prints are ready they are placed face 

 down in a toning mkxture made of stock A, 8 

 ounces, ami stock B, i ounce, taking care that 

 the entire surface of each print is uniformly 

 wetted. They are allowed to remain in this 

 bath, with constant movement by means of the 

 fingers, until the desired color is obtained (usu- 

 ally about 5 minutes). The prints are now im- 

 mersed in salt water (i : 32) for S minutes. 

 They are then exposed for 15 nn'nutes to the 

 fixing bath, consisting of — 



Hyposulphite of soda i ounce 



Sulphite of soda (crystals) 60 grains 



Bora.x ]/, ounce 



Water 20 ounces 



The prints are finally washed for from I to 2 

 hours in running cold water. The toning bath 

 should not be cooler than 40° or warmer than 

 60° F. 



A Nczv Test for Iiidol. 



Herter & Foster have recently described what 

 is stated to be a rapid and accurate method of 

 determining indol, adapted either for eolorimet- 

 ric or gravimetric determinations. To slightly 

 alkaline solutions naphthoquinon sodium mono- 

 sulfonate is added. A blue crystalline com- 

 pound, di-indyl naphtho-ketone mono-sulfonate 

 is produced This is slightly soluble in water, 

 but is readily soluble in chloroform, its solution 

 being red. ( Science, n. s., Vol. XXI, 1905, 

 p. 987.) 



