D. D. VAN SLYKE 



The manometric apparatus of Van Slyke and Neill (18), like 

 the Barcroft-Haldane apparatus, was first developed for determination 

 of the blood gases, and its use then spread to other micro analyses, 

 including the determination of urea, reducing and fermentable sugars, 

 the ammonia yielded by Kjeldahl digestions, amino nitrogen by 

 measurement of the nitrogen yielded by reaction with nitrous acid 

 (18), free alpha-amino acids by measurement of the carbon dioxide 

 yielded by reaction with ninhydrin [RCH(NH2)COOH -> RCHO + 

 CO2 + NH3] (16), organic carbon by measurement of the carbon 

 dioxide evolved by a wet combustion completed in two minutes (17), 

 and various other determinations. In these procedures, the gases are 

 either evolved in, or transferred to, a 50-cc. chamber, provided at the 

 top with small bulbs for measuring 0.5 and 2.0 cc. of gas, and connected 

 at the bottom with a mercury manometer. The evolved gas is brought 

 to 0.5 or 2.0 cc. volume, and its pressure is read on the manometer. 

 In a mixture of gases, each gas can be measured separately by measur- 

 ing the pressure before and after the absorption of each gas by intro- 

 duction of a proper reagent. The carbon combustion method per- 

 mits micro determination of any organic substance, such as the blood 

 fats, that can be isolated by extraction with volatile solvents; the com- 

 bustion also provides a micro measurement of any substance that can 

 be isolated as a carbon-containing precipitate, e. g., sulfate as benzidine 

 sulfate, magnesium as hydroxyquinolate, phosphorus as strychnine 

 phosphomolybdate (14). 



While the Barcroft-Haldane-Warburg apparatus is adapted to 

 following the course of time reactions, the Van Slyke-Neill apparatus is 

 fitted for quick determination of the total amounts of gases evolved by 

 rapid quantitative reactions. Hence the Haldane apparatus has 

 found its chief application in following enzymic time reactions, while 

 the Van Slyke-Neill apparatus is the one usually employed in quantita- 

 tive micro determinations of specific substances. 



Photometric Analysis 



Under the chief initial stimulus of Folin and of S. R. Benedict, 

 during the past forty years chromogenic reactions have been developed 

 for estimating numerous biological substances by producing colored 

 products from them (25). In some cases the colored products are 



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