400 



Dr. H. G. Chapman. On the Weight of [Apr. 21, 



reacting bodies were mixed with saline solution in large tubes for the 

 centrifuge. The tubes were made up to a fixed volume with saline solution 

 and allowed to stand 48 hours for the interaction to take place. The 

 superfluid above the precipitate was removed with a pipette and the 

 precipitate washed five times with saline solution. Each time the precipitate 

 was mixed with 50 c.c. saline solution and the precipitate separated by 

 spinning in the centrifuge. The precipitate was then washed five times in the 

 same way with 50 c.c. distilled water. The precipitate was transferred 

 to small glass tubes with thin walls, weighing about 4 grammes. These tubes 

 could be spun in a small centrifuge and, in this way, the precipitate was 

 washed with absolute alcohol and finally with ether free from water. 

 The tubes with their contents were placed in an oven at 80° C. for several 

 hours and thence were put in a desiccator. The tubes were kept a fixed 

 time in the desiccator and weighed. The tubes of a series were weighed 

 immediately after each other. Owing to the hygroscopic nature of the 

 precipitates the error in the weights of the tubes was found by experiment to 

 be 0'3 milligramme. The mean figure of the several weighings was taken in 

 all cases. 



Experimental Results. 



Experiments were performed to ascertain the weight of precipitate 

 obtained when a measured quantity of antiserum was allowed to interact 

 with increasing weights of homologous protein. It has been shown by Welsh 

 and Chapman* that no precipitin can be detected in the superfluid at the end 

 of an interaction, provided that tlie amount of homologous protein exceeds a 

 certain quantity. In the series to be described the quantity of protein was 

 sufficient to neutralise or precipitatef the precipitin in the antiserum. The 

 superfluids were considered free from precipitin, since they yielded no 

 precipitate on the addition of 144 milligrammes dried egg-white. The results 

 are recorded in Table I. 



Table I. 



No. of 

 tube. 



Weight of 



dried 

 egg-white. 



Volimie of 

 antieeruin. 



Volume of 

 saline solution. 



Weight of pre- 

 cipitate. 



Weight of ))re- 

 eipitiite from 

 1 c.c. iintiBerum. 





niilligniiiimeB. 



c.c. 



e.p.' 



milligrnmnieB. 



milligriunnies. 



1 



14 -4 * 





00 



3 -2 



1 -6 



2 



36 0 ^ 



' I 



50 



3 -5 



1 -75 



3 



144-0 



2 



50 



3 -4 



1 -7 



4 



432 -0 



2 



50 



3-4 



1-7 



* ' Joiirn. of Hygiene,' vol. d, j). 2r)l, 1900. 



+ Compare Weluli and C;hfi]iman, ' Roy. Sue. Proc.,' B, vol. 78, p. 297, 1906. 



