EXPERIMENT STATION BULLETINS. 491 



in a large container ; but at that depth, the insects were not killed. For 

 the reason just stated the mill experiments with ammonia were dis- 

 couraging — although it appeared that the gas, in some instances, might 

 prove to be a desirable fumigant for insects. 



Carlton Tetrachloride. Early in the year 1910, Professor Pettit was 

 urged in behalf of the Michigan Millers to find, if possible, some volatile 

 non-inflamable liquid which might take the place of carbon disulphide as 

 a fumigant for grain in bins. It was suggested to him by Professor 

 Kedziie of the Chemistry department that perhaps carbon tetrachloride 

 might have the qualities desired. Following this suggestion, a series of 

 comparative tests with carbon disulphide and carbon tetrachloride were 

 carried out by Professor Pettit, Mr. M. A. Yothers (who was connected 

 with the department at that time), and the writer, working together. 

 The tests were made in large glass flasks with rubber stoppers. Among 

 the insects in the infested grain used in these tests were the following 

 beetles determined by Prof. F. H. Chittenden of the U. S. Bureau of 

 Entomology : 



RhizopertUa dominica, 

 Latheticus oryzw. 

 LaemopJilacus j)iis^ilJus, 

 Calandra oryzw, 

 TrihoHum ferrugincum. 



A great many Silvanus surinamenms were also used. In these tests 

 carried out in the tight glass flasks, practically all beetles were killed 

 by carbon disulphide used at the rate of 14 dram to a cubic foot of air 

 space. It took II/2 drams of the tetrachloride of carbon to accomplish 

 the same result (at about 70° F.). That is, compared with carbon disul- 

 phide, six times as much carbon tetrachloride was required to accomp- 

 lish effective fumigation. The tests were run from seventeen to twenty- 

 four hours. It should be stated that the liquid insecticide in every case 

 was dropped upon a thin piece of absorbent cotton, which was suspended 

 at the center of the flask. Thus, the broad surface of the cotton enabled 

 the fluid to evaporate rapidly. The liquid carbon tetrachloride was 

 found to be entirely non-inflammable — and its vapor, non-explosive. 



Results of the experiments just described were not published at the 

 time — mainly because the expense for efl'ective fumigation with carbon 

 tetrachloride seemed so great as to be almost prohibitive. Dr. Britton 

 of the Connecticut Experiment Station had given, in 1908, his experi- 

 ments with carbon tetrachloride used as a fumigant against scale in- 

 sects on nursery trees.* 



Later, Feb., 1910, Mr. Albert P. Morse published a note on ''Carbon 

 Tetrachloride vs. Carbon Bisulphid" as a fumigant used in the control 

 of grain and natural history pests.f Mr. Morse stated that "for large 

 cases a strength of one quart to fifty cubic feet is desirable — practically 

 twice that of carbon bisulphid, of which a pint to fifty cubic feet is 

 suflficent." 



In October, 1911, Professor F. H. Chittenden and Mr. C. H. Popenoe 

 of the U. S. Department of Agriculture published a paper on experi- 

 ments carried out with the same chemical used as a substitute for car- 



*.Touriial of Economic Eu(()aioloj,'y, Vol. 1. No. 2, p. 111. 

 tijoxirnal of Economic Entomology Vol. 3, No. 1, p. 104. 



