NUTRIENT AGAR-AGAR 117 



restored. At the end of the time given remove the flame 

 and place the vessel containing the mixture in a large dish 

 of cold water; stir the agar-agar continuously until it has 

 cooled to about 68-70 C., and then add the white of one 

 egg which has been beaten up on about 50 c.c. of water; 

 or the ordinary dried albumin of commerce may be dissolved 

 in cold water in the proportion of about 10 per cent, and used; 

 the results are equally as good as when eggs are employed. 

 Mix this carefully throughout the agar-agar and allow the 

 mass to boil slowly for about another half-hour, observing 

 all the while the level of the fluid, which should not fall 

 below the liter mark. It is necessary to reduce the tempera- 

 ture of the mass to the point given, 68-70 C., otherwise 

 the coagulation of the albumin will occur suddenly in lumps 

 and masses as soon as it is added, and its clarifying action 

 will not be uniform. The process of clarification with the 

 egg is purely mechanical; the finer particles, which would 

 otherwise pass through the pores of the filter, being taken 

 up by the albumin as it coagulates and retained in the 

 coagula. 



At the end of a half-hour the boiling mass may be easily 

 and quickly filtered through a heavy, folded paper filter 

 at the room temperature; as a rule the filtrate is as clear and 

 transparent as agar-agar usually appears. 



It may be well to emphasize the fact that for the filtration 

 of agar-agar no special device for maintaining the tem- 

 perature of the mass, is necessary. Agar-agar prepared 

 after the methods just given should pass through a properly 

 folded paper filter at the rate of a litre in from twelve to 

 fifteen minutes. 



Another plan that insures complete solution of the agar- 

 agar without causing the precipitates often seen when all 



