Some observations on the determination of serum protein levels in cattle.

(1 ml.), and concentrated NH,, (1 ml.) and cooled in an ice bath; 0-2 ml. of N-I2 solution was added very slowly with shaking. Whenthe I2hadall reacted, the solution was diluted with a few ml. of water and most of the NH3 was removed under diminished pressure at 00; the solution was then treated with 1 drop of 10% sodium metabisulphite (Na2S205) solution and acidified at 40° with 3-5N-HCI. The precipitate which separated was almost entirely crystalline. The yield was 34 mg. (91 %). After crystallization from 2 ml. 50% (v/v) methanol, 22 mg. of the compound separated in long needles which had m.p. 219-220° (decomp.). (Found: I, 67*4. C14H80414 requires I, 67-9 %.)