February,’18] hartzell: molasses and adhesiveness 
63 
sprays might be an important problem to be investigated. It was 
believed that ordinary foliage tests for adhesiveness were unreliable 
because of the difficulty of securing quantitative data. To overcome 
this difficulty the writer devised the following method for making 
tests of adhesiveness in the laboratory where the various factors 
might be under control. 
Method and Apparatus 
The gelatin film which had served as photographic negatives on 
5x7 glass plates was removed by means of hot water and the glass 
carefully cleaned by immersion in a sulphuric acid-potassium perman¬ 
ganate bath. Afterwards the plate was washed in hot water and soap 
and then rinsed in clean water. Between thirty and forty plates were 
generally used in each series of tests when they were recleaned and 
used again. Each plate was numbered by means of a series of notches 
in one edge with a file. This system can be modified by numbering 
the glasses with diamond ink. In either method the marks are made 
on an edge or on the surface of the back of the plate. Before a test 
each plate was weighed on a balance sensitive to one-tenth of a 
milligram. 
The brands of arsenate of lead to be tested were used at the rate of 
one gram of paste arsenate of lead or .5 gram of dry lead to each 100 
cc. of distilled water. The samples requiring molasses had the same 
amount of arsenate of lead to which was added 2 cc. of molasses to 
each 100 cc. of water. When the sample was prepared it was care¬ 
fully stirred to place all material in suspension and 10 cc. of the mix¬ 
ture was removed from the flask by means of a pipette and poured 
upon the plate, care being taken to spread the material uniformly 
over the surface. The plate was then placed in a horizontal position 
and allowed to dry at room temperature (near 68° F.) for twenty- 
four hours, when it was reweighed. Each plate then received a drench¬ 
ing with ordinary tap water delivered by means of a sprinkling 
arrangement (described below) whereby the treatment was uniform. 
They were then placed in a vertical position on a drying rack and 
allowed to dry for twenty-four hours and, at the expiration of this 
time, were reweighed. 
The washing outfit consisted of a receptacle holding 3.25 gallons of 
water, tapering to an ordinary shut-off to which a rose sprinkler was 
attached. This water container was suspended by means of a wire. 
The distance from the sprinkler to the plates was exactly two feet. 
Two plates were placed horizontally on a holder in a sink; the water 
turned on and allowed to flow until the receptacle was empty, which 
required exactly two minutes. Of course all the water did not strike 
