APRIL, 190G. THE CHEMICAL NATURE OF SOME INSECT SECRETIONS. 
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what amount of formic acid is present in different forms, and if 
the amount is constant for each species. 
The ant selected for preliminary experiments was Formica 
fuse a, var. gnava Buck., as it was evident from its strongly acid 
odor that formic acid was here present. 
A counted number of the ants were collected in weak ethyl 
alcohol, and then subjected to distillation in a small flask with 
steam. After the distillate had ceased to show an acid reaction, 
a few cubic centimeters of dilute sulphuric acid were added to 
the flask and the distillation continued, in order to ascertain if 
any of the formic acid in the ants had combined with any small 
particles of calcareous earth that might have been present adher- 
ing to their bodies or in the alimentary tract. After removing any 
trace of sulphuric acid from the second distillate by means of 
barium chloride, it was tested for formic acid by the method 
given below, but not even an acid reaction could be obtained. 
The first distillate was then titrated with semi-normal potas- 
sium hydroxide and its acidity noted. The solution of potassium 
formate thus obtained was then heated for several hours at 100 C. 
on a water bath with an excess of mercuric chloride solution and 
the amount of reduced calomel weighed. This method with 
mercuric chloride was found, however, to be very unsatisfactorv, 
as it gave widely divergent results with distillates whose titration 
determinations were very nearly equal. The poor results thus 
obtained were probably due to the presence of organic matter 
other than formic acid, and perhaps in some cases to an incom- 
plete reaction of the alkaline formate. But as no other acid, e. g., 
acetic, butyric, hydrochloric, etc., could be detected, titration with 
semi-normal potassium hydroxide was selected as the most 
reliable method. 
The following table, compiled from a large series of deter- 
minations, shows the amount of formic acid in a number of species 
of Formicidae. As the agreement is in most cases so close, only 
a few determinations are given for each species, besides several 
widely divergent ones that seem worthy of notice. 
