288 
Journal of Agricultural Research 
Vol. VIII, No. 8 
There exists much confusion of names for the ortho lead arsenates. 
There seem to be only two that are commonly manufactured as insecti¬ 
cides. These are the diplumbic and the triplumbic lead arsenates. The 
diplumbic is also called “monoplumbic,” “acid,” and even “pyro.” 
The triplumbic is variously termed “neutral,” “normal,” “basic,” and 
“ortho ” lead arsenate. 
Following is a list of the chemicals used, with the percentage of arsenic 
that each contained as determined by the chemistry department of this 
Station. The arsenic was calculated on a moisture-free basis. 
Per cent 
Arsenic acid, Merck. 51. io 
(Merck & Co., New York and Darmstadt.) 
Ammonium arsenate, Merck. 45-20 
Ammonium arsenite, Merck... 68. 45 
Arsenic trisulphid (yellow), Baker. 59.10 
(J. T. Baker Chem. Co., Phillipsburg, N. J.) 
Arsenic trisulphid (yellow), Merck. 26.12 
Arsenic trioxid, Baker. 73-10 
Arsenic trioxid, Merck. 75-40 
Calcium arsenite, Baker. 51. 20 
Calcium arsenite, Merck. .*....44- 78 
Copper aceto arsenite (Paris green), Ansbacher. 42. 42 
(Ansbacher Insecticide Co., Inc., New York.) 
Copper aceto arsenite (Paris green), Baker.:. 42.85 
Iron arsenate, Merck (a mixture of ferrous and ferric). 38. 40 
Lead arsenate, diplumbic, Baker. 21. 31 
Lead arsenate, triplumbic, Baker... 16. 88 
Lead arsenate, mixture, GrasselU. 19.21 
(Grasselli Chemical Co., Cleveland, Ohio.) 
Lead arsenate, diplumbic, Grasselli.. 21.13 
Lead arsenate, triplumbic, Grasselli. 14. 60 
Lead arsenate, "technical,” mixture, Merck. 19-25 
Lead arsenate, mixture, Swift.20.19 
(Merrimac Chemical Co., Boston, Mass.) 
Lead arsenate, diplumbic, Swift. 
Potassium arsenate, Merck.. 41.32 
Potassium arsenite, Merck. 49- 70 
Sodium arsenate, Merck... 24. 75 
Sodium arsenite, Merck. 58.15 
Zinc arsenite, mixture, Baker... 53- 00 
Zinc arsenite, meta, Baker. 52. 75 
Zinc arsenite, ortho, Baker. 31. 90 
Zinc arsenite, pyro, Baker. 41. 33 
Zinc arsenite, Merck. 35-10 
Zinc arsenite, ortho, California Spray Co.). 32.14 
(California Spray Co., Watsonville, Cal.) 
Zinc arsenite, "Ortho 40,” California Spray Co. 24. 38 
NATURAL PROTECTION OF THE BARK 
It has long been known that the outer portion of the bark of many 
trees is made up of a layer of cork varying in thickness from few to many 
cells. On apple trees (Mains sylvesiris) this forms a well-developed 
