XXI] 



MEAT AND MEAT PRODUCTS 



275 



hydrochloric acid in tube (E). Then add 1 cc. of saturated potassium oxalate solu- 

 tion to the sample in tube (B), introduce a few drops of kerosene and finally add 

 just sufficient saturated potassium carbonate solution to render the mixture alkaline. 

 Place the tubes in position at once, pass air through the apparatus and titrate the 

 standard acid in tube (E) at hourly intervals, until ammonia ceases to be given off, 

 using methyl red, cochineal or congo red as an indicator. If preferred, the ammonia, 

 collected in tube (E), may also be determined by nesslerizing as directed under 



IV, 11. 



1 3 CREATIN.— OFFICIAL. 



Evaporate an aliquot or the remaining portion of the filtrate and washings from 

 the coagulable proteins, 1 1 , (a portion having been used in 12), to 5-10 cc, transfer 

 with a minimum amount of hot water to a 50 cc. measuring flask, keeping the volume 

 below 30 cc, add 10 cc of 2N hydrochloric acid and mix. Hydrolyze in an auto- 



ro Socr/ojy 



FIG. 9. APPARATUS FOR THE FOLIN AMMONIA DETER >IINATION. 



clave at 117°-120°C. for 20 minutes, allow the flask to cool somewhat, remove and 

 chill under running water. Partially neutralize the excess of acid by adding 7.5 cc. 

 of 10% sodium hj^droxid solution, free from carbonates, dilute to tlie mark and 

 mix. Make a preliminary reading on 20 cc. to ascertain the volume to use to obtain 

 a reading of approximately S mm. and transfer to a 500 cc. graduated flask. Add 

 10 cc of 10% sodium hydroxid solution and 30 cc. of saturated picric acid solution 

 (1.2%). Mix and rotate for 30 seconds and let stand exactly 4\ minutes. Dilute 

 to the mark at once with water, shake thoroughly and read in a Duboscq colori- 

 meter, comparing the color with N/2 potassium dichromate solution, set at 8 mm. 

 If the reading is too high or too low (above 9.5 or below 7 mm.), calculate the 

 quantity necessary to obtain a reading of about 8 mm. The strength of the dichro- 

 mate solution used must be checked against a standard creatin solution. To obtain 

 the values, divide 81 by the reading and multiply by the volume factor to obtain mg. 

 of creatinin; this value multiplied by 1.16 gives creatin, which, divided by the weight 

 of the sample and multiplied by 100 gives the per cent of creatin. 



