Hygroscopic Properties of Black Powder

G. B. Taylor
1919 Journal of Industrial & Engineering Chemistry  
chemical manufacturers for the purpose of introducing t h e process into the plants on a commercial scale. Some months later all of the cooperation t h a t could be handled advantageously was effected and the constantly increasing pressure of war problems employing the laboratories and personnel made it advisable t o withdraw the offer, which was done on Iiovember I, 1 9 1 7 .~ Shortly after the signing of the armistice it was decided t o reopen the offer of cooperation and a n announcement t o
more » ... n announcement t o t h a t effect was issued on March 17, 1 9 1 9 .~ First-The work upon war problems was prdctically over and men and funds were again arailable for the work for which this laboratory was planned. Second-Several manufacturers stated t h a t they could not enter into the cooperative agreement when first announced because a t t h a t time their entire staff was devoted to work on hand, but that now their resources were larger, war work was over, parts of the plant were idle, and they would like t o be put in position t o utilize the information originally given t o other cooperators and upon the same terms. Third-Publications of the completed work will not be ready for an indefinite period, since the scope of the investigations is undergoing great expansion, and it is considered desirable t h a t the manufacturing process first be firmly established in this country. I n the interim cooperators are furnished immediate reports on the latest developments. Fourth-It seems desirable t h a t a number of plants work upon t h e same problem in order t h a t the best commercial installation be ultimately obtained. Although the development was delayed somewhat by war conditions, the large-scale manufacture of phthalic anhydride is now proceeding in a satisfactory manner, and it is believed t h a t eventually the details of the factory units will be so worked out t h a t this process will be t h e most economical and practicable known for making phthalic anhydride. I n fact, phthalic anhydride may become one of the cheapest organic compounds. It is interesting t o note t h a t the phthalic anhydride produced by this process is of a remarkable degree of purity. Naturally it is free from chlorine or sulfur compounds, common impurities in phthalic anhydride as formerly found on the market. Many data on t h e work have accumulated and new facts are continually being discovered. A series of papers descriptive of the work is now in preparation and will appear a t intervals when the status of this and other investigations will permit. The reasons for this action were several. t h a t of whether black powder in which a small part of the potassium nitrate had been replaced by potassium perchlorate was less resistant t o moisture than straight black powder. This led t o a brief study of the conditions under which black powder absorbed atmospheric moisture, t h e results of which are presented in this report. The fact that powder is more effective in the moisture-free condition is embodied in the old admonition t o "keep.your powder dry." The methods followed were those of a previous investigation on moisture absorption by detonators.1 The rate of moisture absorption in a saturated atmosphere was determined a t 2 j 0 C. by exposing the material in shallow flat-bottom crucibles. Ordinary ' quart jars closing with glass tops and spring clamps were filled about an inch deep with distilled water; in each jar was placed a copper wire tripod for supporting one crucible. The jars were then closed and submerged completely in a large water thermostat electrically heated and stirre'd, and controlled by a toluene thermoregulator within * O . O I O of 2 j 0 C. Two grams of the material whose rate of moisture absorption was t o be determined were spread evenly over the bottom of the crucible (3. 7 cm. in diameter), the crucible brought t o 2j0, and placed in one of t h e jars. After a certain number of hours the crucible was removed, placed in a weighing bottle, and weighed. Each result was obtained from a separate crucible, as it was found unsatisfactory. t o return the same crucible t o the jar, on account of change in temperature of t h e crucible during weighing and slight losses in moisture while handling. It was found in the previous investigation* t h a t the moisture absorbed in a given time by pure salts under the conditions above outlined was independent of the weight of salt taken within certain limits (0. j t o 2 . 0 g.) and also independent of the degree of fineness t o which the salt was ground. The relative rates of moisture absorption of different salts were found t o be proportional t o the difference between the vapor pressures of their saturated solutions and the partial pressure of water vapor in the surrounding atmosphere. It follows t h a t when this difference is zero or when t h e partial pressure of water vapor in the surrounding atmosphere is less than the vapor pressure of the saturated solution of the salt no moisture will be absorbed. I n the latter case a moist salt would dry out. I n American practice black powder is a mixture of 7 5 per cent potassium or sodium nitrate, I O per cent sulfur, and I j per cent charcoal. Moisture absorption is largely due t o the nitrate or soluble constituents. Charcoal plays a small part. E X P E RI & ! I E NT A L Two samples of black powder were submitted by the Ordnance Department for test. These were given the laboratory numbers M -2 3 3 2 and M -2 3 3 3 . The size of grain appeared t o be F. For comparison, the
doi:10.1021/ie50119a011 fatcat:55skzsdh3ffuppzlcaadiwglei