44 CHEMICAL STATICS 



pure iron oxide. If this is not the case, then they must be dis- 

 solved in warm water and recrystallized. At a temperature of 

 less than 0° C. the crystals can be dried in the air without de- 

 composition. 



Preyer states that, of all kinds of blood, that of the horse is 

 best adapted for the production of very large quantities of pure 

 haemoglobin. 



For a variety of rapid methods of preparing small quantities 

 of crystals from the blood of different species the reader is re- 

 ferred to the monograph on the Crystallography of Haemoglobins 

 by Reichert and Brown (28). 



6. Crystallizable Egg- Albumin. — The method of Hopkins and 

 Pinkus ( 1 0) is universally employed for the preparation of this protein. 



Two hundred cc. of egg-white obtained from newly-laid fowls' 

 eggs are mixed with an equal bulk of saturated ammonium sul- 

 phate solution, the latter being very gradually added and the mix- 

 ture stirred briskly with an egg-beater between each addition. 

 It is then allowed to stand over night. The mixture is then filtered 

 and to the clear filtrate more saturated ammonium sulphate solu- 

 tion is added until a permanent precipitate is obtained. Distilled 

 water is then added, a few drops at a time, until the solution is 

 just clear again. Ten per cent acetic acid solution is then added 

 drop by drop until a slight but definite precipitate has appeared. 

 The bottle is then immediately stoppered and allowed to stand. 

 After 24 hours an abundance of uniformly crystalline precipitate 

 has settled out consisting of rosettes of needles. If a somewhat 

 greater proportion of acetic acid is employed the rosettes are 

 mixed with sheaths and fan-shaped aggregates of crystals. Re- 

 crystallization of this first product is carried out by filtering off 

 the crystals from the mother-liquor, redissolving in a moderate 

 amount of water, acidifying with a few drops of dilute acetic 

 acid and adding saturated ammonium sulphate solution until a 

 faint turbidity is produced. In 24 hours a large proportion of 

 the protein will have recrystallized. This process may be re- 

 peated 5 or 6 times in the course of a week. The crystals which 

 are finally obtained may be freed from inorganic contamination 

 by prolonged dialysis against running distilled water. 



7. Ovovitellin. — The following method of preparation is that 

 employed by Osborne and Campbell (23), modified by Plimmer 

 (25) and further modified by the author (33). 



