276 METHODS OF ANALYSIS [Chap. 



The use of Kober's shade and the painting of the plunger, as suggested for this 

 nephelometer, assists in getting a sharper end point, relieves the eye strain and 

 may be employed if desired. 



Example. — 20 grams of meat are extracted with water as in 9, and the extract 

 diluted to 500 cc. ; 150 cc. of this latter solution (equivalent to 6 grams of meat) are 

 treated as in 11. The filtrate thus obtained is then evaporated and hydrolyzed as 

 above and then diluted to 50 cc. ; 25 cc. of this last solution are treated with sodium 

 hydroxid solution and picric acid solution as directed above and diluted to 500 cc. 

 This latter solution gives a reading of 9 mm. 



-Q X ^ = 18 mg. creatinin; 



0.018X1.16X100 -„,^ 

 t; = 0.3o% creatin. 



(In chopped meat, sausage, deviled meat, etc.) 



17 Qualitative Test. — Tentative. 



Treat 5-6 grams of the sample with boiling water for 2-3 minutes, cool the mix- 

 ture and test the supernatant liquid with iodin solution. In using this test, a small 

 amount of starch may be present as the result of the use of spices. If a marked 

 reaction is given, however, it may be concluded that starch or flour has been added, 

 and a quantitative determination maj^ be made. The qualitative method may be 

 replaced by a microscopic examination, which discloses not only the presence of 

 added starch, but also the variety employed. 



18 Mayrhofer Method, Price Modification*. — Tentative. 



Treat in a 200 cc. beaker 10 grams of the finely divided sample with 75 cc. of an 

 8% solution of potassium hydroxid in 95% alcohol by volume and heat on a steam 

 bath until all the meat is dissolved (30-45 minutes). Add an equal volume of 95% 

 alcohol, cool and allow to stand for at least an hour. Filter by suction through a 

 thin layer of asbestos in a Gooch crucible. Wash twice with warm 4% potassium 

 hydroxid in 50% alcohol by volume and then twice with warm 50% alcohol. Dis- 

 card the washings. Retain as much of the precipitate in the beaker as possible 

 until the last washing. Place the crucible with contents in the original beaker, 

 add 40 cc. of water and 25 cc. of concentrated sulphuric acid. Stir during the addi- 

 tion of the acid and make sure that the acid comes in contact with all the precipi- 

 tate. Allow to stand about 5 minutes, add 40 cc. of water and heat just to boiling, 

 stirring constantly. Transfer the solution to a 250 cc. graduated flask, add 2 cc. 

 of 20% phosphotungstic acid solution, allow to cool to room temperature and make 

 up to the mark with water. Filter through a starch-free filter paper, pipette 100 

 cc. of the filtrate into a 200 cc. graduated flask, neutralize with sodium hydroxid 

 .solution, make up to volume and determine the dextrose present in a 50 cc. portion 

 of the filtrate, as directed under VIII, 25, titrating the cuprous oxid precipitate 

 as directed under VIII, 29. The weight of the dextrose multiplied by 0.9 gives 

 the weight of the starch. 



GLYCOGEN. 



19 Qualitative Test^. — Tentative. 



Boil 50 grams of the macerated sample with 50 cc. of water for 15-30 minutes. 

 Filter the broth through moistened filter paper or fine linen. To a portion of the 

 filtrate in a test tube add a few drops of a mixture of 2 parts of iodin, 4 of potassium 



