AGRICULTURE: JOHNS AND JONES 
365 
each of the Hnes gives evidence of the phenomenon; i.e., if the residual 
fringes are obHque, each such Hne is strongly heHcal in appearance. 
Hence the equation for the residual fringes naay be assumed to be 
n \ = {e—e') [/z cos { r — a) — cos i] 
when e and are the thicknesses of the two half silver plates, fj, their 
index of refraction, i the angle of incidence, r the angle of refraction of 
an incident ray, and where a is the outstanding angle between the faces 
of the differential glass wedge, e—e^ thick at the ray in question. The 
possibility of throwing these fringes into any order of size, their small 
extent, sharpness and great abundance of light constitute their value 
for measurement. 
THE PROTEINS OF THE PEANUT, ARACHIS HYPOGAEA 
By Carl 0. Johns and D. Breese Jones 
PROTEIN INVESTIGATION LABORATORY. BUREAU OF CHEMISTRY. DEPARTMENT 
OF AGRICULTURE. WASHINGTON^ 
Communicated by R. Pearl. March 27, 1917 
During the last ten years the culture of peanuts has increased rapidly 
in the United States. This increase is partly due to the fact that the 
boll weevil has made the growing of cotton unprofitable in various sec- 
tions of the South and peanuts are now grown as a supplementary crop. 
Most of the peanuts thus produced are sold to the oil mills to be pressed 
for the oil which they contain. Shelled peanuts yield from 40 to 50% 
of oil. This edible oil compares favorably with olive oil and is used for 
culinary purposes and for making olemargarin. Press cake from shelled 
peanuts contains about 45% of protein (N x 6.25). This cake is 
ground to a meal which is rapidly finding favor as a cattle food. Pea- 
nut meal is now quoted at $35 per ton and peanut oil at $1.05 per gallon. 
Previous to the present work, the only published experiments on the 
protein of the peanut seem to be those described by Ritthausen^ in a 
paper which appeared in 1880. This author found that the proteins of 
the peanut consist chiefly of globulin and his analytical data led him to 
beHeve that only one globulin is present. 
We have made fractional precipitations of the proteins extracted by 
sodium chloride solutions from oil-free peanut meal and have isolated 
two globuHns, one of which is present only to a small extent. The glob- 
ulin composing the greater part of the protein in the peanut is pre- 
cipitated, when in 10% sodium chloride solution, by adding ammonium 
sulphate to 0.2 of saturation. To this globulin we have given the name 
arachin. After filtering off the arachin, the second globuHn may be ob- 
