April, '15] 



SCOTT: BARIUM SULPHIDES 



207 



of barium penta-sulphide (BaSs) which when reduced to dryness under 

 suitable conditions forms barium tetrasulphide (BaS4H20) and free 

 sulphur. This dry material also contains some thiosulphate (BaSoOs) = 

 As prepared for the writer's experiments it analyzes approximately as 

 follows : 



The tetrasulphide occurs in the form of reddish yellow crystals of 

 the rhombic system and it is readily soluble in cold water. The free 

 sulphur and thiosulphate also largel}^ dissolve in the tetrasulphide 

 solution, leaving about 4 per cent of the material as insoluble residue. 



During the dormant season of 1913-14 the writer conducted experi- 

 ments for the control of the San Jose scale in Virginia, West Virginia, 

 Pennsylvania and New York and in no case could there be observed 

 any material difference in the killing effect of the barium product and 

 lime-sulphur solution. The results of an experiment conducted in a 

 ten-year-old apple orchard at Sleepy Creek, W. Va. are shown in 

 Table I. Trees moderately infested with the San Jose scale were 

 selected and the spraying was done on December 5, 1913. In making 

 the examination on April 29 and June 8, the old weather-beaten scales 

 that were evidently dead before the spraying was done, or that died 

 naturally during the winter, were, of course, not counted, so that the 

 percentages given in Table I include only those scales that could be 

 expected, normally, to pass the winter alive. 



BaS4H20 . . . 

 Free sulphur 



BaSsOs 



Impurities. . 



Spraying Experiments 



Table I. Sax Jose Scale Experiment, Sleept Creek, W. Va., December 5, 1913 



Plot 



Materials 



Oz. to 1 gal. 

 Water 



Per cent Scale 

 Dead 4-29-14 



Per cent Scale 

 Dead 6-8-14 



8 

 9 



10 



2 



3 

 4 

 5 

 6 



Calcium thiosulphat* 



Calciiim sulphide 



Lime-sulphur sol. 33° B . . 

 Lime-sulphur sol. 33° B. . 

 Baritoi-sulphur sol. 33° B 

 Barium-sulphur sol. 33° B 

 Barium-sulphur sol. 33° B 



Dry barium-sulphur 



Dry barium-sulphur 



Check 



TJnsprayed 



16 

 6 

 20 

 15 

 20 

 15 

 28 

 12 

 12 



59 

 83, 

 95 

 95 

 951 

 95 

 100 

 96 

 95 

 5U 



60 

 90 



The barium-sulphur solution mentioned in Table I is analogous to 

 Hme-sulphiir solution and was made by boiling the simple sulphide 



