XXI] MEAT AND MEAT PRODUCTS 273 



finely divided and retains a great deal of liquid. To prevent the extract or the 

 coagulum from coming into contact with the linen before passing through the sand, 

 pour the extract slowly into a slight depression in the center of the sand or, better 

 yet, into a thip. film of absorbent cotton, 1^ inches in diameter, laid over a depres- 

 sion in the sand. The coagulum remains on the cotton and its return to the beaker 

 is facihtated thereby. If the cotton is not broken up by needless stirring, it can be 

 taken out of the beaker with a glass rod and returned to the sand each time a partial 

 extract is to be filtered. Care is necessary to prevent loss through bumping, on 

 account of sand in the beakers during the final extractions. P]ach partial extract 

 should be boiling hot at the time filtration begins. 



7 DETERMINATION. 



To the extracts, prepared as directed in 6, add 50 cc. of magnesia mixture [I, 4 (C) J 

 and stir thoroughly. Allow to stand 15 minutes, add 25 cc. of ammonium hy- 

 droxid (sp. gr. 0.90), cover and allow to stand 3 days. Filter and wash the pre- 

 cipitate with 21% ammonium hydroxid. Dissolve the precipitate on the filter paper 

 and that remaining in the beaker in nitric acid (1 to 1) and hot water, receiving 

 the solution in a 400 cc. beaker. Neutralize with ammonium hydroxid, make sUghtly 

 acid with nitric acid, add 5 grams of ammonium nitrate and determine phosphorus 

 as directed under I, 6. 



8 TOTAL NITROGEN.— OFFICIAL. 



Proceed as directed under I, 18, 21 or 23, using about 2 grams of the fresh 

 sample. In the Kjeldahl and Gunning methods digest with sulphuric acid for at 

 least 4 hours; in the Kjeldahl-Gunning-Arnold method for 2 hours after the mix- 

 ture has become clear. 



9 SOLUBLE AND INSOLUBLE NITROGEN.— TENTATIVE. 



Exhaust 7-25 grams of the sample depending upon the water content in the fol- 

 lowing manner: Weigh into a 150 cc. beaker, add 5-10 cc. of cold (15°C.) ammonia- 

 free water and stir to a homogeneous paste. Then add 50 cc. of cold water, stir 

 every 3 minutes for 15 minutes, let stand for 2-3 minutes and decant the liquid upon 

 a quantitative filter, collecting the filtrate in a 500 cc. graduated flask. Drain the 

 beaker, pressing out the liquid from the meat residue by the aid of a glass rod. 

 Add to the residue in the beaker 50 cc. of cold water, stir for 5 minutes and, after 

 standing 2-3 minutes, decant as before. If a considerable portion of the meat 

 is carried over onto the filter, transfer it back to the beaker by means of a glass 

 rod. Repeat the extractions, using the following additional amounts of cold water: 

 50, 50, 25, 25, 25 and 25 cc. After the last extraction transfer the entire insoluble 

 portion to the filter and wash with three 10 cc. portions of water, allowing the ma- 

 terial to drain thoroughly after each addition of water. Dilute to the mark, mix 

 thoroughly and determine the total soluble nitrogen in a 50 cc. aliquot as directed 

 under I, 18, 21 or 23. Subtract the percentage of soluble nitrogen from the per- 

 centage of total nitrogen, 8, to obtain the percentage of insoluble nitrogen. To 

 obtain the percentage of insoluble protein multiply the percentage of insoluble 

 nitrogen by 6.25. 



10 CONNECTIVE TISSUE NITROGEN.— TENTATIVE. 



Exhaust 10 grams of the sample with cold water as directed under 9, and boil the 

 exhausted residue repeatedly with successive portions of about 100 cc. of water 

 until the total hot water extract amounts to approximately 1 liter. Filter, concen- 

 trate and determine nitrogen in the concentrated extract. Multiply the percentage 

 of nitrogen so obtained by 5.55 to obtain the percentage of nitrogenous substances 

 of the connective tissue. 



