232 
A hderhcdden's Reaction 
such organs, however, it is necessary to test them again by boiling vhth 
distilled water, filtering, and testing the filtrate with Ninhydrin. 
Technique. 
The dialysing capsules most convenient for this reaction are those 
supplied by Schleicher and Schiill, known as No. 579 A. 
These capsules must be tested before being used in order to find 
out whether they are impermeable to albumin, but still allow peptone 
to pass through without any difficulty. It will generally be found that 
a certain percentage of the capsules are defective in respect to per¬ 
meability, some being too porous and allowing albumin to pass through, 
whilst others are too dense and resist the free diffusion of peptones. 
In order to test them the capsules are first softened by soaking in dis¬ 
tilled water. Then into each capsule is put 2-5 c.c. of a 5 per cent, 
solution of egg albumin, prepared from the white of a fresh egg. Each 
capsule is then placed in a small Erlenmeyer flask, or a bottle, containing 
20 c.c. of distilled water. The flask should have a neck sufficiently 
wide to receive the capsule readily, the neck being slightly longer than 
the capsule. 
Toluol is then poured into the capsule and also upon the water in 
the flask, until it forms a layer about 1 cm. thick. The flasks, with 
their contained capsules, are then inciibated at 37° C. and allowed to 
stand for about 16 hours. 
The dialysate is then tested for the presence of albumin either by 
means of the Biuret reaction, or by adding sulpho-salicylic acid. In the 
former case, 10 c.c. of the dialysate is mixed in a test-tube with 2-5 c.c. 
of a 33 per cent, solution of caustic soda. Then, by means of a pipette, 
1 c.c. of a 0-2 per cent, solution of copper sulphate is carefully run on 
to the surface of the mixture and if a violet ring is formed at the junction 
of the two liquids, the presence of albumin is denoted. Any capsules 
which are thus shown to be permeable to albumin should be discarded. 
The dialysate may also be tested by adding to 10 c.c. of the dialysate, 
1 c.c. of a 33 per cent, solution of sulpho-salicylic acid, the presence 
of albumin being indicated by the liquid developing an opalescent or 
milky appearance. 
The capsules found to be impermeable to albumin are washed in 
running water for 24 hours, and then dipped in boiling distilled water 
for half-a-minute. They are then tested for permeability to peptone. 
For this purpose into each capsule is placed 2-5 c.c. of a 1 per cent, 
solution of silk peptone and the fluid dialysed for 16 hours in 20 c.c. 
