33 2 PHYSIOLOGICAL CHEMISTRY. 



of concentrated ammonia and shake the tube vigorously. Note 

 the production of a brick-red color. Take 1-2 c.c. of this colored 

 solution, add 10-20 c.c. of hydrochloric acid (sp. gr. 1.19), 3 c.c. 

 of chloroform and 2-4 drops of ferric chloride solution and care- 

 fully mix the fluids iwthout shaking. Diacetic acid is indicated by 

 the chloroform assuming a violet or blue color ; if diacetic acid is 

 absent the color may be yellow or light red. 



H OH H 



/3-OXYBUTYRIC ACID, H C C C COOH. 



I I I 



H H H 



This acid does not occur as a normal constituent of urine but is 

 found only under pathological conditions and then always in con- 

 junction with either acetone or diacetic acid. Either of these bodies 

 may be formed from /3-oxybutyric acid under proper conditions. It 

 is present in especially large amount in severe cases of diabetes and 

 has also been detected in digestive disturbances, continued fevers, 

 scurvy, measles and in starvation. It is probable that, in man, (3- 

 oxybutyric acid, in common with acetone and diacetic acid, arises 

 principally from the breaking down of fatty tissues within the or- 

 ganism. The condition in which large amounts of acetone and 

 diacetic acid, and in severe cases /?-oxybutyric acid also, are excreted 

 in the urine is known as "acidosis.". In diabetes the deranged 

 metabolic conditions cause the production of great quantities of 

 these substances which lead to an acid intoxication and ultimately 

 to diabetic coma. 



Ordinarily /3-oxybutyric acid is an odorless, transparent syrup, 

 which is Isevorotatory and easily soluble in water, alcohol and ether ; 

 it may be obtained in crystalline form. 



EXPERIMENTS. 



i. Black's Reaction. Inasmuch as the urinary pigments as well 

 as any contained sugar or diacetic acid will interfere with the deli- 

 cacy of this test when applied to the urine directly the following 

 preliminary procedure is necessary: Concentrate 10 c.c. of the 



(&) One gram of />-amino-acetophenon dissolved in 100 c.c. of distilled water 

 and enough hydrochloric acid (about 2 c.c.) added, drop by drop, to cause the 

 solution, which is at first yellow, to become entirely colorless. An excess of 

 acid must be avoided. 



Before using, a and b are mixed in the ratio 1 : 2. 



