ACETONE AND ACETOACETIC ACID 149 



(see below). (Commercial varieties of acetic acid frequently con- 

 tain substances which behave like acetone. Blank determinations 

 should always be made and corrections made accordingly.) The 

 precipitate in the mercury reagent is, however, estimated nephelo- 

 metrically. In this case the distillate which should measure 

 75-100 c.c. is allowed to stand half an hour, then transferred to 

 a graduated cylinder and diluted until an opalescence that can 

 be conveniently read is obtained. The turbidity occasioned by 

 0.05 mg. of acetone diluted to 100 c.c. is a convenient strength 

 for this purpose, although considerably larger or smaller amounts 

 give good results. With heavy opalescence it is desirable after 

 diluting to a certain volume, say 250 c.c. to remove an aliquot 

 portion with a pipette and dilute this appropriately. A solution 

 containing a known amount of acetone (a convenient stock solu- 

 tion contains about 0.03 mg. acetone per c.c.) is distilled into an 

 excess of reagent (the solution cannot be added directly to the 

 reagent as a lower result is obtained than when distilled) and this 

 distillate which is to be used as the standard is diluted as above. 

 Read in the nephelometer against this standard, taking the read- 

 ings as quickly as possible after filling the tubes as the suspension 

 settles slowly. 



If the unknown suspension is diluted so as to be not more than 

 20 per cent different from the standard and if comparisons are 

 made in considerable depths of solution (50 to 60 mm.) no cor- 

 rections are necessary. If the two agree within 10 per cent accurate 

 comparison may be made at less depths. If divergences are greater 

 and accurate results are desired, Kober's correction equation 

 must be used (see discussion of nephelometer, page 146). 



ACETONE, ACETOACETIC ACID AND /3-HYDRO- 

 XYBUTYRIC ACID 



Marriott-Scott-Wilson Method 1 



(a) Acetone and Acetoacetic Acid. Draw 10 c.c. of blood 

 from a superficial vein by a sterile graduated syringe and run it 

 into about 40 c.c. of 0.5 per cent potassium oxalate solution. 

 Fit up a Kjeldahl distillation apparatus, using an 800 c.c. flask, 



1 Scott-Wilson: Jour, of Physiol., 1911, 42, 444. Marriott: Jour. Biol. 

 Chem.. 1913, 16, 295. 



