284 METHODS OF ANALYSIS [Chap. 



Measure off in B 10 c,-. or less, as the case may be, of the solution of the sample 

 containing not more than 20 mg. of amino nitrogen (about 1-2 grams of the sample) 

 and allow it to run into D. Connect D with the motor as shown in Fig. 10 and 

 shake for 5 minutes. 



If the solution of the sample is viscous and threatens to foam over, rinse out B, 

 and then through it introduce a little caprylic alcohol into D, or, if it is known 

 beforehand that the sample will cause excessive foaming, introduce a little caprylic 

 alcohol into D through B, rinsing B with alcohol and ether or drying with a roll of 

 filter paper before adding the solution of the sample. 



During the shaking there is an evolution of nitrogen mixed with nitric oxid,the 

 gases being collected in F: Force all the gas in D into F by opening a and filling 

 D with liquid from A. Connect F with the Hempel pipette and force the gas into 

 the latter by means of the leveling bulb, allowing the cock a to remain open during 

 this and the succeeding operation in order to permit displacement of the liquid in 

 D by the nitric oxid formed in the interval. Connect the driving rod with the 

 pipette by lifting the hook from the shoulder of D and placing the other hook, on 

 the opposite side of the driving rod, over the horizontal lower tube of the pipette. 

 Shake the pipette rather slowly for a minute which, with any but almost completely 

 exhausted permanganate solutions, completes the absorption of nitric oxid. Then 

 return the gas to the burette, adjust the level with the leveling bulb and note the 

 volume of nitrogen, the temperature and barometric pressure, and calculate the 

 volume of nitrogen under standard conditions of temperature and pressure. Ob- 

 tain the corresponding weight of nitrogen, divide the latter by 2, and from the 

 quotient calculate the apparent per cent of amino nitrogen in the sample. Cor- 

 rect the result for a blank test performed as above, using 10 cc. of water instead of 

 the solution of the sample. The amount of gas obtained in the blank is usually 

 0.3-0.4 cc, and nitrite solutions giving a much larger correction should be 

 rejected. 



In the case of beef extracts and similar preparations 5 minutes is sufficient time 

 to allow for the completion of the reaction in D. In general the same time serves 

 for the decomposition of alpha-amino acids but with ammonia, methylamin and 

 most amines other than alpha-amines 1-1| hours should be allowed. For determi- 

 nations on such substances mix the solution of the sample with the reagents as de- 

 scribed above, allow the mixture to stand in the apparatus till the end of the re- 

 quired time, and conclude the reaction by shaking the apparatus with the motor for 

 2-3 minutes. Continue the determination from this point as directed above. 



47 ACID ALCOHOL-SOLUBLE NITROGENi^.— TENTATIVE. 



Transfer 10 cc. of an aqueous solution of the sample (10 grams of the sample 

 dissolved in sufficient water to make 100 cc.) or, if the sample is insoluble in water, 

 1 gram of the sample and 10 cc. of water, to a 200 cc. glass-stoppered measuring 

 cylinder, add 1.2 cc. of 12% hydrochloric acid, mix and add absolute alcohol to the 

 200 cc. mark. Mix thoroughly and set aside for several hours. If necessary make 

 up to volume, filter, transfer 100 cc. of the filtrate to a Kjeldahl flask, evaporate the 

 alcohol on a water bath and determine nitrogen in the residue as directed under I, 



18, 21 or 23. 



48 CREATIN.-OFFICIAL. 



Dissolve about 7 grams of the sample in cold (20°C.) ammonia-free water in a 

 150 cc. beaker, transfer the solution to a 250 cc. measuring flask, dilute to the mark 



