132 



PRACTICAL PHYSIOLOGY. 



fxx. 



8. Preparation of Hippuric Acid. (a.) Take 100 cc. of cow's 

 or horse's urine, and evaporate it to one-sixth its bulk ; add hydro- 

 chloric acid, and set it aside. The brown mass is collected, dried 



between folds of blotting- 

 paper, redissolved in a very 

 small quantity of water, and 

 mixed with charcoal, then 

 filtered and set aside to 

 crystallise. It is not quite 

 pure and contains a brownish 

 colouring-matter. 



FIG. 6 9 .-Hippuric Acid. 



(6.) Boil horse's urine with milk 

 of lime = a copious precipitate. 

 Filter off the bulk of the precipi- 

 tate through flannel, and filter 

 again through paper. Concentrate 

 the filtrate to one-sixth of its volume and add hydrochloric acid = a copious 

 precipitate of prismatic crystals of hippuric acid. After twenty-four hours 

 decant the fluid from the crystals, redissolve the latter in hot water, and filter 

 through animal charcoal. 



9. Kreatinin (C 4 H 7 N 3 0) is related to the kreatin of muscle. 



If kreatin be boiled with acids or with water for a long time, 



it loses water, and becomes converted into a strong base 

 krsatinin. 



Quantity, 0.5 to i gram (7 to 15 grs.). It is easily soluble in water and 

 alcohol, and forms colourless oblique rhombic crystals. It unites with acids, 

 and also with salts, chiefly with ZnCl. 2 ; the kreatinin-zinc-chloride is used as 

 a microscopic test for its presence. It rarely occurs as a deposit, and nothing 

 is known of its clinical significance. 



10. Preparation of Kreatinin. (a. ) Take 250 cc. of urine, precipitate it with 

 milk of lime, and filter. Evaporate the filtrate to a syrupy consistence, and 

 extract it with alcohol. Filter, and to the filtrate add a drop or two of a 

 neutral solution of zinc chloride, and set the vessel aside. After a time 

 kreatinin-zinc-chloride (CjHjKjO, ZnCl 2 ) is deposited on the sides of the vessel. 



(b.) To half a litre of urine add baryta-mixture (p. 124) until no further 

 precipitation takes place ; filter, and evaporate the filtrate to a thin syrup on 

 a water-bath, add to this an equal volume of alcohol, allow it to stand for 

 twenty-four hours in the cold, whereby the salts are separated, filter, and to 

 the filtrate add 1-2 cc. of a concentrated alcoholic solution of zinc -chloride. 

 After a time kreatinin-zinc-chloride separates as a yellow crystalline powder. 

 After two to three days filter, wash with alcohol, and dissolve in warm water, 

 and decompose it by boiling for half an hour with hydrated lead oxide 

 or carbonate of lead. Filter while hot, decolorise the filtrate with animal 

 charcoal, filter again, evaporate to dryness, and extract the kreatinin from the 

 residue with alcohol in the cold. A small quantity of kreatinin remains un- 

 dissolved. 



