340 PHYSIOLOGICAL CHEMISTRY 



16. Detection of Calcium Phosphate. Evaporate the filtrate from the 

 coagulable proteins, on a water-bath, until crystals begin to form. It may be 

 necessary to concentrate to 15 c.c. before any crystallization will be observed. 

 Cool the solution, filter off the crystals (reserve the filtrate), and test them as 

 follows : 



(a) Microscopical Examination. Examine the crystals and compare them 

 with those in Fig. no. 



(b) Dissolve the crystals in nitric acid. Test part of the acid solution for 

 phosphates. Render the remainder of the solution slightly alkaline with 



ammonia, then acidify with acetic acid and add am- 

 monium oxalate. Examine the crystals under the 

 microscope and compare them with those in Fig. 

 140, page 476. 



17. Detection of Lactose. Concentrate the fil- 

 trate from the calcium phosphate until it is of a 

 syrup-like consistency. Allow it to stand over night 

 and observe the formation of crystals of lactose. 

 Make ^ following experiments. ' 



(a) Microscopical Examination. Examine the 

 crystals and compare them with those in Fig. 109, page 335. 



(b) Fehling's Test. Try Filing's test upon the mother liquor. 



(c) Phenylhydrazine Test. Apply the phenylhydrazine test to some of the 

 mother liquor according to the directions given on page 22. 



18. Milk Fat. (a) Evaporate the ether filtrate from the casein (Experiment 

 13) and observe the fatty residue. The milk fat was carried down with the 

 precipitate of casein and was removed when the latter was treated with ether. 

 If centrifugated milk was used in the preparation of the caseinogen the amount 

 of fat in the ether filtrate may be very small. To secure a larger yield of fat 

 proceed according to directions given under (b) below. 



(b) To 25 c.c. of whole milk in an evaporating dish add a little sand or filter 

 paper and evaporate the fluid to dryness on a water-bath. Grind or break up 

 the residue after cooling and extract with ether in a flask. Filter and remove 

 the ether from the filtrate by evaporation. How can you identify fats in the 

 ethereal residue? 



19. Saponification of Butter. Dissolve a small amount of butter in alcohol 

 made strongly alkaline with potassium hydroxide. Place the alcoholic-potash 

 solution in a casserole, add about 100 c.c. of water and boil for 10-15 minutes or 

 until the odor of alcohol cannot be detected. Place the casserole in a hood and 

 neutralize the solution with sulphuric acid. Note the odor of volatile fatty acids, 

 particularly butyric acid. Under certain conditions the odor of ethyl butyrate 

 may also be detected. 



20. Detection of Preservatives. (a) Formaldehyde. In these 

 tests two controls should be run, one with pure milk and one with 

 milk to which a very small amount of formaldehyde has been added. 



I. Leach's Hydrochloric Acid Test. Mix 10 c.c. of milk and 10 c.c. of con- 

 centrated hydrochloric acid containing about 0.002 gram of ferric chloride in a 

 small porcelain evaporating dish or casserole and gradually raise the temperature 



