IO2 BACTERIOLOGICAL LABORATORY TECHNIC 



phthalein as an indicator, and after finding how much of a nor- 

 mal solution is required to neutralize 990 c.c. (i,oooc.c. 10 c.c. 

 used for titration) this normal solution is added. The mixture 

 thus neutralized is then boiled for five minutes and the weight re- 

 stored. After boiling, from .5 percent to 1.5 percent normal hydro- 

 chloric acid solution is added and the acidity thus produced is 

 spoken of as +.5 per-cent or +1.5 percent as the case may -be. 



Upon boiling, the albumins are coagulated by heat, and the 

 phosphates are thrown down. The acid re-dissolves the latter. 

 The former must be removed by filtration. The filtrate is a clear 

 straw-colored fluid of an acid reaction which should not become 

 cloudy upon boiling. This is then run into flasks or test-tubes and 

 sterilized. 



The second method is much more convenient, and is prepared 

 by adding 3 grams of Liebig's beef extract to a litre of water, and 

 adding the peptone and salt, as in the previous method, and pro- 

 ceeding as before. To filter the bouillon, the filter paper must 

 be folded many times, and the funnel must be carefully cleaned. 



GELATINE. 



To make gelatine, bouillon is made to which gelatine is added in 

 order to render it solid. The following steps are taken: 



a. Take a litre of water in a saucepan and add chopped beef or 

 beef extract as in bouillon. After standing over night squeeze 

 the beef and extract the juice. 



b. Add i percent peptone, 5 percent salt, 10 percent to 15 per- 

 cent best gelatine and weigh. 



c. Heat until ingredients are all dissolved. 



d. Neutralize, gelatine is highly acid and requires much alkali. 



e. Boil five minutes and restore weight, boil till albumin coagu- 

 lates. 



f. Cool to 60 C. and add an egg well beaten up in water. 



g. Boil slowly till all the egg is coagulated. This clears the 



