UNIVERSITY OF CALIFORNIA agricultural Experiment Station College of agriculture e - j - wickson, director BERKELEY, CALIFORNIA CIRCULAR No. 72 (October, 1911) SALT IN CYANIDS GEO. E. COLBY AND GEO. P. GRAY. A recent publication of the United States Department of Agri- culture 1 has shown that under certain conditions the presence of common salt in commercial cyanids produces a decomposition of the hydrocyanic acid gas. Since there is a large amount of cyanid now being used for fumigation showing chlorids equivalent to over 18 per cent sodium chlorid (common salt), which according to the above mentioned tests would decrease the efficiency one-third, requiring the use of one-half more cyanid to produce the same amount of hydro- cyanic acid gas, the Insecticide Laboratory undertook a special study of the subject, which will be reported in detail in a later publication. The purpose of the present preliminary statement is to furnish the users of this grade of cyanid the practical results of this work. The tests referred to above were made with a solution of the cyanid, — one part in two parts water added to two parts acid and two parts water, and this method will here be called the "wet" process. The results for amounts of decomposed hydrocyanic acid obtained upon treating cyanids by this method are entirely different when the "dry" process of using the cyanid is employed, approximating closely the method universally employed in actual fumigation work. In this method one part of dry cyanid is throv/n into a mixture of one part acid and three parts water. When fumigation was first developed by this station the production of ammonia gas by the decomposition of the hydrocyanic acid gas was studied, 2 and the substitution of the "dry" method of generating was chiefly to avoid the injury to the foliage due to the ammonia. The apparatus used in the "dry" process in this laboratory work was similar to that employed by the Government chemist: the tube into the generating flask simply had a foot bent at the lower end upon Avhich a weighing bottle containing the weighed cyanid rested; this was introduced into the flask and when ready a twist of the tube upset the cyanid into the mixture of acid and water just below. This is practicnllv what is done in fumigation work when the dry cyanid is dropped into the acid in the generator. i Bureau of Entomology, Bulletin No 90, Part TTT. 2 Calif ornia Station Bulletin No. 79. (See also Bulletin No. 12!!.) .B bJD O ^ c- H O ■» >^ e6 l>» t>» U O m Q o co 00 CO CO i— i o o OS o ■* LO co CO os © o <* I- a? O c3 .Bm 1 1 4-3 ~ SR ^ CD ^3 ^ O l> O CO 03 >— i cu •• CD a> T3 ad Q o o CO EH M XI "S* o CD EH ° s I 2 S'g 1Z o it- CD ftS £.9 ^ 9^ p. Oj3 t« fl CO " © 30 £8 a Ho CO CD CO o lo co o CO as OS CO OS CM CO CO 00 oo 00 CO LO co co CO CO CO CO CO CO 00 CO CO CO LO CO co lo CO LO CO CO lo CO LO oo 1— 1 OS CO OS CO OS CO OS CO OS CO OS CO OS CO CO CO CO o CO o CO o CO o CO o CO oo co CO co oo oo oo 00 00 o b- o "* LO lO lO lO LO LO co CD t> 00 o o o o o o o o o oo 00 00 oo 00 oo OO 00 00 00 Sample 805 showed by the "wet" process a decomposition of hydrocyanic gas varying from 8.88 per cent to 16.88 per cent; the "dry" test on this sample showed a decomposition of the gas from 0.7 per cent to 2.86 per cent, and another sample, 806, containing a large quantity of sodium chlorid, showed a very large percentage of decomposed cyanhydric gas by the "wet" process. Two other samples, Nos. 807 and 808, showed a somewhat higher decomposition by the "dry" method than No. 805, but still the results are very much less than in the tests made by the "wet" method. It will be noted that the powdered cyanid (No. 805) when treated by the "dry" process showed considerably greater amounts of decom- posed cyanhydric gas than when the materials were used in lumps, indicating a slight action in the direction that results by testing the cyanid in solution. The users of cyanid should appreciate that when they are operating with cyanids rich in common salt they are sure to get decomposition of the gas if they use the finer cyanid in the bottom of the case. It is probably also wise to take care that the cyanid does not become wet by exposure to the air. The practical conclusions are: First — Where there are no chlorids present the total available cyanogen is nearly all converted into hydrocyanic acid gas. Second — When chlorids are present and the gas is generated from solid lumps a very small amount pf decomposition occurs. Third — Cyanid in solution suffers very great decomposition during generation when chlorids are present. Fourth — The commercial cyanids now being used are good for fumigation purposes even if they contain the largest amount of com- mon salt yet found, provided the hydrocyanic acid gas is generated by the method usually followed in practice.