I,VDUSTRlAL A,VD ENGINEERING CHEMISTRY
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pletely. With fortieth molar solutions there was again a tendency to stay in suspension and no precipitate formed when hundredth molar solutions were used. The precipitate obtained from the twentieth molar solutions after filtering and washing was found to be electrically neutral. The addition of a small amount of ferric chloride tended to peptize the precipitate. The particles were reduced in size and stayed well in suspension. The precipitate was difficult to filter, but after being filtered and washed, it was found to be electrically positive. LE.4D h S E N A T E - I t was impossible to prepare a good positively charged lead arsenate from lead arsenate precipitated from lead nitrate with disodium arsenate, but it was very easy to make it from lead arsenate precipitated from lead acetate. It is known that an acid lead arsenate is made if lead nitrate is used but that a basic lead arsenate is formed from the acetate. Analyses showed that it was the basic arsenate which so readily took on a positive electric charge. When the acid lead arsenate made from lead nitrate was treated with sodium hydroxide or leadacetate, it was converted to the basic arsenate and then readily took on a positive charge if treated with a slight excess of lead acetate. COPPERARSENATE-A study of the copper compounds of arsenic indicated that a positively charged copper arsenite may be made from copper chloride or sulfate, but a copper arsenate was made difficult to prepare from these salts. The desired copper arsenate was readily formed from a copper salt of a weak acid such as the acetate. OTHERARSENATES-studies of various arsenates and arsenites of zinc, chromium, cerium, magnesium, and calcium confirmed the foregoing observations. The results of these experiments indicated that a positively charged arsenical was one, the particles of which contained an adsorbed metallic ion, such as iron, aluminium, zinc, lead, copper, magnesium, or calcium.* The conditions favoring the adsorption of the ion were found to be the formation of a basic arsenic compound in the presence of a slight excess of a soluble metallic salt, preferably in some cases the salt of a weak acid. The combination may be roughly represented as follows:
++
Vol. 17, No. 5
a dew every night, the adherence of the positive calcium arsenate was 259 per cent better than the standard material. A second test was run for 9 days, during which there were two rains (0.46 and 1.02 cm. or 0.18 and 0.40 inch, respectively) and a dew each night. The adherence of the special material was 245 per cent greater than the standard calcium arsenate. In a third test the plants, after being exposed to the weather for 7 days during which time there were two rains thoroughly sprinkled tfoequal the washing effect of a very heavy rain. Analyses indicated that in this test the adherence of the positive calcium arsenate exceeded the standard by 196 per cent. Summary
The common arsenical spraying and dusting materials as now manufactured either have no electric charge or a negative charge when wet, and are therefore easily washed off the plants by the action of rain or dew. The common basic arsenical materials may be so manufactured or treated that they will have an adsorbed positive ion which will give the arsenical particle a positive electric charge when wet. Such positively charged arsenical particles are attracted and held to the negatively charged leaf surface, resisting the washing effect of rains and dews. A positive calcium arsenate has been made under commercial manufacturing conditions and tested in the field, where the adherence was found to be from 196 to 259 per cent greater than the standard calcium arsenate.
A Constant-Level Regulating Device' By R. L. Stehle RZCGILLUNIVERSITY, MONTREAL, CAXADA
+ +
(FeAsOJ, Fe+++ 3'21HzO (CUS(AsO4)z)t CU++ 2(CHsCOn)- HAO
Some hydroxides or oxides of the metal may be, and no doubt usually are, present. Working on this basis it was found possible to go a step further and impart the desired electric charge to a manufactured arsenical by treating it with the proper metallic salt. The arsenate may be made by any method desired and the positive electric charge imparted to it as the last step in its manufacture. Calcium Arsenate That Adheres
Calcium arsenate has become the standard boll weevil poison, and such large amounts have been used that a t times there has been a shortage of arsenic. The use of a positively charged calcium arsenate would resist the washing effect of rains and dews, reduce the number of dustings necessary for the control of the weevil, and serve to relieve the shortage of arsenic. Such a calcium arsenate has been made, during the past season, under commercial manufacturing conditions and has been tested in the field. In the tests standard calcium arsenate manufactured under the same conditions as the positive calcium was used for comparison. The plants were dusted when dry and exposed to the ordinary weather conditions. Analyses showed that at the end of 5 days, during which there were two rains (0.30 and 0.51 cm., or 0.11 and 0.20 inch, respectively) and 3
U.S. Patent 1,376,153(April 26, 1921).
the siphon breaks. In the device figured this has been obviated by
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