XXI] MEAT AND MEAT PRODUCTS 279 



26 DETERMINATION. 



Extract 100 grams of finely ground meat by boiling repeatedly with successive 

 small portions of water, decanting the extracts through a muslin or paper filter 

 into a casserole, and concentrate the combined extracts to a volume of about 50 cc. 



Introduce 50 cc. of the ferrous chlorid solution and 50 cc. of 10% hydrochloric acid 

 into the flask, close the stop-cock of the funnel, open the pinch-cock on the deUvery 

 tube, move the end of the latter so that escaping air will not pass into the measuring 

 tube, and boil the contents of the flask until the air is expelled, as indicated by a 

 slight pressure against the fingers when the rubber tubing is compressed after mo- 

 mentary removal of the flame. Now close the delivery tube with the pinch-cock 

 and place the exit end beneath the measuring tube. Introduce the concentrated 

 extract of the sample into the flask, a little at a time, through the funnel tube, 

 opening the pinch-cock on the delivery tube and boiling the contents of the flask 

 at intervals to force the nitric oxid gas into the measuring tube. Finally rinse the 

 casserole and the funnel tube with a little boiled water, add the rinsings to the con- 

 tents of the evolution flask in the manner just described and boil until nitric oxid 

 no longer passes over into the measuring tube. Calculate the volume of nitric 

 oxid at 0°C. and 760 mm. pressure. One cc. of nitric oxid at 0°C. and 760 mm. 

 pressure is equivalent to 0.004512 gram of potassium nitrate. 



Phenoldisulphonic Acid Method^. — Tentative. 



27 REAGENTS. 



(a) Phenoldisulphonic acid solution. — Heat 6 grams of phenol with 37 cc. of con- 

 centrated sulphuric acid on a water bath, cool and add 3 cc. of water. 



(b) Standard comparison solution. — Dissolve 1 gram of pure, dry potassium ni- 

 trate in water and dilute to 1 liter. Evaporate 10 cc. of this solution to dryness 

 on a steam bath, add 2 cc. of the phenoldisulphonic acid solution, mix quickly and 

 thoroughly by means of a glass rod, heat for about a minute in a steam bath and 

 dilute to 100 cc. One cc. of this solution is equivalent to 0.1 mg. of potassium ni- 

 trate. Prepare a series of standard comparison tubes by introducing amounts 

 ranging from 1-20 cc. of this solution (0.1-2.0 mg. of potassium nitrate) into 50 cc. 

 Nessler tubes, adding 5 cc. of strong ammonium hydroxid to each and diluting to 

 50 cc. These standard tubes are permanent for several weeks if kept tightly 

 stoppered. 



28 DETERMINATION. 



Weigh 1 gram of the sample into a 100 cc. flask, add 20-30 cc. of water and heat 

 on a steam bath for 15 minutes, shaking occasionally. Add 3 cc. of saturated silver 

 sulphate solution for each per cent of sodium chlorid present, then 10 cc. of basic 

 lead acetate solution and 5 cc. of alumina cream, shaking after each addition. 

 Make up to the mark with water, shake and filter through a folded filter, returning 

 the filtrate to the filter until it runs through clear. Evaporate 25 cc. of the filtrate 

 to dryness, add 1 cc. of the phenoldisulphonic acid solution, mix quickly and thor- 

 oughly by means of a glass rod, add 1 cc. of water and 3 or 4 drops of concentrated 

 Bulphuric acid and heat on a steam bath for 2-3 minutes, being careful not to char 

 the material. Then add about 25 cc. of water and an excess of ammonium hydroxid, 

 transfer to a 100 cc. graduated flask, add 1-2 cc. of alumina cream if not perfectly 

 clear, dilute to the mark with water and filter. Fill a 50 cc. Nessler tube to the 

 mark with the filtrate and determine the amount of potassium nitrate present in 



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