J* 



-c 



this acid with strong sulphuric acid at 100 C. He runs air-free 



carbon dioxid through a flask containing the citric 



acid until all air is displaced from the apparatus. 



He then adds concentrated sulphuric acid, heats to 



100 C., drives over the evolved carbon monoxid with a 



stream of air-free carbon dioxid, and collects the gas in a 



eudiometer over a sodium hydrate solution. The method 



as carried out by him is accurate, but requires consider- 



able care and attention to remove the air from the appa- 



ratus completely, to insure that all evolved carbon mon- 



oxid is swept over into the eudiometer, and to prevent 



the strong sodium hydrate solution from sucking back 



into the reaction flask containing carbon dioxid and sul- 



phuric acid. In the apparatus proposed by us no attempt 



is made to remove the air before reaction, the volume of 



evolved gas being simply measured by the increase in 



volume of the total gases after reaction. Thus the Spica 



method as carried out in this apparatus is as follows : 



Place about 0.2 gram of citric acid in the reaction 

 chamber (B), open the stopcock (X) and bring the 

 liquid (in this case a strong sodium hydrate solution) to 

 the zero mark (G) in the eudiometer tube by raising or 

 lowering the leveling tube (E). The air in the appa- 

 ratus is then at atmospheric pressure. Close (X). To 

 (A) add about 15 cc of concentrated sulphuric acid. 

 Lower the leveling tube so that the air in the apparatus 

 is under reduced pressure. By carefully opening the 

 stopcock (X) run in exactly 10 cc of the sulphuric acid. 

 Close (X) and heat to about 100 C. by means of the 

 heating coil until the reaction is complete. Let the 

 apparatus stand until the absorption of other gases (sul- 

 phur dioxid, etc.) is complete and it has reached room 

 temperature. Bring the gas in the apparatus to atmos- 

 pheric pressure by means of the leveling tube (E). The 

 gas reading in the eudiometer minus 10 cc (for the added 

 sulphuric acid) equals the volume of the evolved gas at 

 the existing temperature and pressure. The apparatus 

 has been used in this laboratory with accurate results 

 to estimate citric acid by the Spica method and for the 

 estimation of amino acids by the Van Slyke method, 1 FIG.S. Appara- 

 which depends on the evolution of nitrogen by the 

 action of nitrous acid on the amino acids. The appa- 

 ratus is readily cleaned by taking it apart at the ground joint (F). 



tus for meas - 



[Cir. 80] 



d. chem. Ges., 1910, 48(3) : 3170. 



o 



