UNIVERSITY OF CALIFORNIA agricultural experiment Station 
 
 COLLEGE OF AGRICULTURE E - J - WiCKSON. d. rector 
 
 BERKELEY, CALIFORNIA 
 
 CIRCULAR No. 73 
 
 (October, 1911) 
 
 PURE INSECTICIDES 
 
 BY 
 
 C. W. WOODWORTH. 
 
 Most of the chemicals used as insecticides and fungicides are 
 entirely satisfactory when of low grade, provided the approximate 
 strength is known. The California Insecticide Law permits any grade 
 to be sold, requiring a statement of its composition and providing 
 that it shall not be lower than within 5 per cent of the percentage 
 claimed on the label. 
 
 For high grade goods the limit of variation allowed under the law 
 is too great, since it does not provide a means of fixing a minimum 
 guarantee above 95 per cent, and then only when labeling them 100 
 per cent. 
 
 Because of this 5 per cent variation permitted by the law the actual 
 guarantee is below the label guarantee to the extent of the amounts 
 shown in the following table : 
 
 Label guarantee 
 
 Actual guarantee 
 
 % 
 
 % 
 
 100 
 
 95 
 
 99 
 
 94.05 
 
 98 
 
 93.1 
 
 97 
 
 92.15 
 
 96 
 
 91.2 
 
 95 
 
 90.25 
 
 For the purpose of providing for the more accurate specification 
 of high grade goods the following plan is suggested : 
 
 1st. Use the term "Pure" without the designation of per cent for 
 goods that do not fall below 95 per cent. 
 
 2nd. Use the form "Guaranteed not less than 96%" for goods 
 that Avill not fall below that figure, and a similar form for still higher 
 grades. 
 
The following list of chemicals and crude drugs have been regis- 
 tered under the percentages indicated, but are doubtless in most cases 
 of high enough grade to justify the use of the higher forms of guar- 
 antee suggested above : 
 
 Caustic Soda (NaOH), 98%. 
 Hydrated Lime (Ca20H), 
 Borax (2B,0 3 . Na,0 + 10 H 2 0), 
 
 99.6%, 99%, 95-99%. 
 Hellebore, 100%. 
 Tobacco, 100%. 
 Quassia, 100%. 
 Sabadilla, 100%. 
 Staphisagria, 100%. 
 Carbolic Acid (C 6 H 5 OH), 96%, 95%. 
 Cresylic Acid (C 8 H 4 OHCH„), 95-99%. 
 Carbon Tetrachlorid (C Cl 4 ), 99.92%, 
 
 99.7%, 97-99.9%. 
 Bluestone (CuS0 4 + 5H,0), 99.5%, 
 
 99%, 98-99%, 97i/>-98%, 96.5%, 
 
 95%. 
 Copperas (FsS0 4 + 7H,0), 98%, 
 
 97%, 96%. 
 Corrosive Sublimate (HgCL), 99.5%, 
 
 99%, 98-99.9%. 
 
 Sulphuric Acid (H 2 S0 4 ), 99.5%. 
 Distillate 28°, 100%. 
 Distillate 32°, 100%. 
 Napthalene (C 10 H 8 ), 100%, 99%%, 
 
 98%, 96.3%, 95-100%. 
 Oil Myrbane, 100%, 99%. 
 Oil Pennyroyal, 99%. 
 Oil Peppermint, 99%. 
 Pyrethrum, 99%. 
 Pyrethrum flowers, 100%. 
 Camphor, 98-100%. 
 Permanganate of Potash (KMn0 4 ), 
 
 99%, 98%. 
 Sodium FJuorid (NaF), 100%, 95%. 
 Sulfur (S), 99.7%, 99.5-100%, 99.5%, 
 
 99-100%, 99%, 98-991/,%, 98-99%, 
 
 98%, 97%, 95%. 
 Carbon Bisulfid (CS,), 97-99.9%, 
 
 97%. 
 
 Dealers who wish to list their goods in accordance with these sug- 
 gestions will be permitted to amend their application for License 
 without further cost by simply filing a statement at the Insecticide 
 Laboratory. 
 
 When goods are guaranteed "Pure," or 100 per cent, they are 
 considered as complying with the law if they do not fall below 95 
 per cent. Dealers using the expression "not less than" thereby ex- 
 pressly waive the 5 per cent variation permitted under the law and 
 become liable if their goods do not come strictly up to their guarantee. 
 No dealer is required by law to make these higher guarantees, but 
 when they have goods which they can safely guarantee higher than 
 the law requires they have the right to the commercial advantage of 
 their superior product, hence this plan for a voluntary higher guar- 
 antee than provided by the Insecticide Law.