172 STERILIZATION AND DISINFECTION 
weight of the albumin residue. From 1 gm. of egg albumen dried to 
constant weight determine the percentage of moisture. From the data 
thus obtained it is easy to determine the amount of boiled distilled 
water which must be added to the filtrate (100 c.c.) to make 1 per cent 
dried albumen solution. 
We will suppose that the dried filter paper to be used 1n filtering the 
albumen solution weighs 1.570 gms. and this same paper with the 
undissolved albumen residue (also dried at 100° C. to constant weight) 
weighs 1.965 gms., then the weight of the undissolved dried albumen 
residue equals 0.395 gm. We will suppose that 1 gm. of albumen loses 
0.126 gm. on drying, or 12.6 per cent moisture. 0.395 gm. raised to its 
normal air moisture (0.395 gm.+12.6 per cent of 0.395 gm.=0.444 gm.) 
and subtracted from 2.00 gms. leaves 1.556 gms., the amount of albumen 
that passed through the filter paper. 12.6 per cent of 1.556 gms. = 0.196 
gm. and 1.446 gms. less 0.196 gm.=1.360 gms. which represents the 
amount of albumen, dried to constant weight, that passed into solution. 
Therefore to make a 1 per cent solution it is necessary to add enough 
boiled distilled water to the filtrate to make 1/100, in this case add water 
up to the 136 c.c. mark. We now havc a1 per cent solution sufficiently 
accurate for all practical purposes. 
This albumen test solution is now ready for use but it must be kept 
in mind that it is readily attacked by microbes. However, if carefully 
prepared with pure albumen, boiled distilled water, in sterile vessels, 
and put on ice or in a cool place, it will keep for perhaps four days. 
Any quantity of albumen solution may be made, it merely being 
advised not to prepare more than may be required for the tests contem- 
plated. 
(b) Gravimetric Method B. In a dried and tarred platinum dish 
place 5 c.c. of the albumen filtrate (2 gms. in 100 c.c. of boiled distilled 
water), evaporate over water bath and dry to constant weight, and from 
this determine the percentage of albumen in the solution and the 
amount of water that must be added to the albumen filtrate to make 
1 per cent. 
(c) Nitrogen Determination. By means of the Kjeldahl apparatus 
determine the percentage of nitrogen representing the albumen in 
solution. 
Having prepared the egg albumen solution the next step is to make 
the phenol control solution, the primary stock solutions of the disin- 
fectants to be tested for coagulating powers, and, from these, the 
secondary or sub-stock solutions, from which the final test dilutions 
are made as the experiment progresses. 
