CAPTAIN NOBLE AND MB. E. A. ABEL ON FIEED GUNPOWDER. 
67 
2. Solid Residue. — Preparation of the Residue for Analysis. 
The residue, as collected for analysis, consisted of one or more large masses, besides 
a quantity in a more or less fine state of division which had been detached from the 
sides of the vessel. The appearance presented by the large pieces themselves indicated 
that they were by no means homogeneous, and they evidently differed in some respects 
from the ^smaller particles just referred to ; moreover the foreign matters (metal and 
glass) could not be expected to be uniformly distributed throughout the mass, and a 
chemical examination of the latter clearly indicated that certain constituents existed in 
different proportions in the upper and lower parts of the residue. For these reasons, 
in order to insure the attainment of results correctly representing the composition of 
the residue, it appeared indispensable to operate upon the entire quantity at one time, 
with the view of determining the total amount of matter insoluble in water, and of 
preparing a solution of uniform composition in which the several components of the 
residue could be estimated. As the investigation proceeded, much inconvenience and 
delay were experienced from the necessity of working with very large quantities (from 
400 to 100 grms.), which rendered the filtrations and washings protracted operations, 
and necessitated dealing with very large volumes of liquid. It was therefore attempted 
to expedite the examination of the residues by so preparing them that only portions 
might be operated upon at one time in conducting the individual determinations of 
the constituents. The impossibility of pulverizing and mixing the residue by any ordi- 
nary mode of proceeding, on account of the rapidity with which oxygen and water were 
absorbed from the air, was demonstrated by two or three attempts. An arrangement 
was therefore devised for performing the operation in an atmosphere of pure nitrogen. 
The gas employed was prepared in the following manner : — 
A gasometer filled with air was submitted to a gentle pressure, causing the air to 
flow very slowly through a delivery-pipe to a porcelain tube filled with copper turnings 
and raised to a red heat. To remove any traces of oxygen, the nitrogen passed from 
the tube through two Woulfe’s bottles containing pyrogallic acid dissolved in a solu- 
tion of potassium hydrate; and, finally, to remove moisture, it passed through two 
U-tubes filled with pumicestone moistened with sulphuric acid. The nitrogen thus 
obtained was collected in india-rubber bags ; the residue was placed in a closed mill, 
connected by an india-rubber tube with the gas-bag, which was subjected to a consider- 
able pressure to establish a plenum in the mill. The substance was then ground, and 
allowed to fall into bottles, which were at once sealed. By this treatment a sufficient 
degree of uniformity in different samples of any particular residue was generally 
attained ; in some cases, however, the state of division of the substance was not suffi- 
ciently fine to secure such intimacy of mixture as would preclude the occurrence of 
discrepancies in the analytical results furnished by different samples. It was therefore 
found necessary to return occasionally to the employment of the entire residue obtained 
in one experiment for determining its composition. 
K 2 
