US2375175A - Smokeless powder process - Google Patents

Description

Fatented May 1, M45

SMOKELESS POER PROCESS Charles Earnest Silk, Alton, BL, assignor to Olin Industries, Ina, East Alton, IlL, a corporation of Delaware No Drawing. Application January 1, 1944, Serial No. 516,716

17 Claims.

This invention relates to explosives and particularly to smokeless powder and provides an improved process of manufacturing spherical grains thereof. This application is a continuation in part of my prior copending application, Serial No. 333,107 filed'May 3, 1940.

' Spherical grains of propellent powder in accordance with U. S. Patent 2,027,114 have heretofore been manufactured by a procedure in which a lacquer, formed by dispersing a smokeless powder base in a suitable solvent, was distributed in the form of particles in a non-solvent medium, these particles being subsequently transformed to globules at atmsopheric pressure and hardened, by progressively raising the temperature and vaporizing the solvent, to form the desired gelatinized grains.

An object of the present invention, generally stated, is to provide an improved process for the manufacture of spherical grains of propellent powder.

Another object of the invention is to provide a process for the manufacture of spherical grains of propellent powder wherein a smaller quantity of solvent is required than heretofore. A further object of the invention is to provide a process whereby the formation of spherical grains of smokeless powder is facilitated and expedited.

Other objects will become apparent to those skilled in the art When the following description is read.

In accordance with the present invention, generally stated, the foregoing objects may be accomplished by distributing particles of a lacquer, formed by dispersing a smokeless powder base in a limited quantity of volatile solvent, in a suitable non-solvent medium, the quantity of solvent utilized being insufficient, at normal atmospheric temperature, to render the lacquer workable to the extent necessary. The present invention contemplates that thelacquer be rendered workture. While the lacquer isbeing rendered and maintained fluid by the combined action of solvent and heat (under pressure) the mixture is agitated, so as to cause the particles of lacquer to assume a globular shape. When the particles of lacquer have assumed the desired shape, they are set in that shape by reducing the pressure on the mixture. The pressure reduction may be accomplished either by venting the sealed vessel in which the mixture is being agitated while maintainingthe heat (which results in evaporation of the solvent from the formed globules) or by lowering the temperature of the mixture (which rsults in freezing the formed globules). By'either of these methods reduction of pressure within the vessel to atmospheric may be accomplished; or the pressure reduction may be interrupted at an intermediate point dependent upon the degreeof venting or the degree of chilling. In any event, after the pressure hasbeen reduced and the globules are'set, the solvent is further removed from the globules, as by distilably fluid by the-combined action of solvent and heat, and particularly that the temperature of the mixture be elevated to a point at which the heat augments the action of the solvent in increasing the fluidity of the lacquer particles. In order to prevent neutralization ofthe heat effect by evaporation of the solvent, however, an important aspect of the present invention resides in the feature that the pressure on the mixture is increased to an extent sufficient to inhibit evaporation of the solvent at the temperatures encountered which are higher than the normal (atmospheric pressure) boiling point of the mixlation.

In accordance with this procedure, therefore,

advantage is taken of the fact that a rise in temperature of a given solution of a smokeless powder base such as nitrocellulose in a suitable solvent will be accompanied by a marked decrease inviscosity. By carrying out the step of shaping the grains at an elevated pressure it becomes possible to resort to higher temperatures and thus to reduce the amount of solvent required in the process and also to produce more perfectly shaped grains of improved uniformity of granulation in a shorter time. In accordance with one embodiment of the invention, by low ering the temperature of the suspension after the particles of lacquer have become transformed into the desired globular shape, the particles become frozen in the acquired shape and the volatile solvent may be removed, as by evaporation, from the grains while in suspension without impairing their form. In accordance with another embodiment, the sealed treating vessel is vented after the particles of lacquer have become transformed into the desired globular shape and the reduction of pressure incident to such venting causes the volatile solvent to be removed from the grains while in suspension. In either vent by evaporation. amounts of solvent were required'and a protracted and carefully controlled distillation period for the removal of solvent was necessary in order to secure grains of the desired shape and.

density.

' guanidine.

and density result even with rapid rates of evaporation of the solvent.

These advantages were not obtainable in the processes'heretofore in use in the manufacture of spherical grains of propellent, powder since the step of shaping the grains occurred at normal atmospheric pressure and at or slightly above normal atmospheric temperature andthe temperature then raised to effect the removal of sol- Acc'ordingly, larger The process of this invention may The base may, for example, consist of nitrocellulose of any desired degree of nitration, viscose ity, or physical form or of, amixture of different types or nitrocellulose. The nitrocellulose may be replaced wholly or in part by other high molecular weight smokeless powder bases, such as nitrostarch, capable of being dispersed in a volatile solvent and of being'converted to a coherent gelatinized solid on evaporation of the solvent. The smokeless powder base may also contain other active explosive ingredients such as nitro,

aromatic compounds, for example, diand trinitrotoluene, or nitric acidesters oi polyhydroxy compounds such as nitroglycerin, nitroglycol, nitromannite, and pentaerythritol tetranitrate, or other explosiveorganic nitrates or nitro compounds, for example, nitramines such as nitrosecuring desired characteristics such as, for example, stabilizers, deterrents, waterproofing agents, and other substances adapted to produce specific effects.

Although the smokeless powder base employed may be one which has been brought to a condi- .tion of stability by previous treatments, thepropowder base, it may be used in the fibrous state,

either after having been stabilized by suitable treatments or as freshly nitrated cellulose which has merely been washed to remove occluded acid.

a The starting material may likewise consist of previously colloided nitrocellulose which 'may have become deteriorated by-the eiTect of lon storage even to such an extent as to contain decomposed spots of relatively high acidity. Simbe applied in the manufacture of'smooth-surfaced spherical grains of any suitable smokeless powder base.

, quer byevaporation.

non-solvent selected be one which is not substantially miscible with the solvent selectt- :l.

The solvent used to disperse the smokeless powder base in lacquer form is one which is substantially immiscible with the non-solvent mediumv above referred to and which is sufllciently volatile as to be readily removed from the lac- I Generally, the solvent should have a boiling point below or not greatly in excess of 100 C. although solvents of some.-

what higher boiling points may at times be suitable. vent medium and nitrocellulose as the smokeless powder base, esters such as ethyl acetate, 'iso-' propyl acetate, butyl acetate, or ethyl iormate, or

- water-immiscible ketones such as methyl ethyl I medium other than water, solvents such as ace- Other agents may be includedfor tone or ether-alcohol may be used, provided they are not substantially miscible with the non-solvent medium selected.

The amount of solvent most suitable for use in any given instance will depend largely on the particular smokeless powder base employed and the temperatureof the'graining operation. For

example, in a case where pyronitrocellulose containing about 12.5% nitrogen is formed into .spherical grains at a temperature of 70-85 C.,

an amount of ethyl acetate equal to IVs-4 times the weight of powder base may be employed. As a general rule, the lower the viscosity oi the nitrocellulose, the lower the proportion .of solvent need. be. For example, with a wood nitrocellulose having a viscosity of about 1'7 seconds (Her cules method) advantageous results are accomplished when the amount or ethyl acetate employed is 3.65 times the weight of the nitrocellulose, whereas with nitrocellulose having a viscosity of about 5 seconds, the proportion of ethyl acetate to nitrocellulose may be reduced to 3- to-l.

powder base, alimited quantity of solvent therefor, and water or other suitable non-solvent medium, suflicient in amount to permit adequate a itation of the mixture, and preferably having a. protective colloid dispersed therein, are 'mixed at a sufliciently elevated temperature that a fluid After agitation for a sumcient period, the particles assume a spherical shape probably largely due to the efi'ect oi. interfacial tension forces.

When this stage has been reached, the pressure on the mixture is reduced either by venting to ilarly, the raw material may consist of colloided nitrocellulose-nitroglycerin powders.

The medium in which the steps of grain formation and subsequent removal of solvent occur is one which is not a solvent for the smokeless' Water constitutes the medium powderbase. which'is preferred as a general rule and from the economical standpoint for such use. It will be understood, however, that other nonsolvent liq- .uids may at times be useful, for example, solvent naphtha orchlorinated hydrocarbons such as carbon tetrachloride, provided always that the the atmosphere or by rapidly cooling the mixture, which results in setting the globules of lacquer in their acquired spherical shape, in the one case by reducing the influence of heat and in the other case by reducing the influence of solvent toward fluidity or the lacquer. Alter the globules are thus set and while still maintained in suspension, additional heat may be supplied to remove solvent from the globules by distillation. In order to effect substantially complete removal of solvent the temperature may be gradually increased duringthe distillation peri- When water is employed as the non-sol- H In order to form the desired globules of the v smokeless powder base lacquer, the smokeless The agitation is sufas'mwc od, the pressure upon the mixture during this final distillation stage being preferably at or about atmospheric.

It will be understood that other desired ,in-

greclients may be present during the graining op-' station. Where the smokeless powder base consists of deteriorated or unpurified nitrocellulose, the treatment is preferably carried out in'the I presence of a mild alkaline material, such as calcium carbonate, suflicient to neutralize the excess acidity present in the starting material. Furthermore, the desired amount of stabilizers such as diphenylamine, or a dialkyldiphenylurea such as methyl centralite, deterrents such as dinitrotoluene or dibutyl phthalate, accelerators such as nitroglycerin, or waterproofing agents may be present in the mixture. Protective colloids'such as starch, gum arabic, dextrin, animal glue or bentonite may be utilized to facilitate and control the granulation process, as disclosed in the said U. 8. Patent 2,027,114. In order to control the density of the product, solutes may be utilized as disclosed in U. S. Patent 2,160,626.

The process may be controlled so that grains of predetermined size and density are produced by suitable adjustment of various factors, as disclosed in the aforesaid U, S; Patent 2,027,114. Thus the average grain size may be decreasedby increasing the violence of the agitation or by increasing the amount of protective colloid present,

or by decreasing the viscosity of the smokeless powder base lacquer, as by the use of more solvent or by raising the temperature of the graining operation. The average grain size may be increased by changing these rection.

In order to illustrate the process of this invention, a detailed description is given below of the practice followed in manufacturing smooth-surfaced spherical grains of smokeless powder with the use of finely divided nitrocellulose as starting material. This raw material may be obtained, for example, by grinding granular colloided nitrocellulose in the presence of water and screening the resulting powder through a suitable screen, for example, one finer than 8 mesh.

The steps of forming the grains and removing the volatile solvents may conveniently be carried out in a single vessel provided with the necessary facilities, such as means for heating and cooling the contents, for example a suitable jacket through which cooling or heating fluid may be circulated; suitable means for agitation, such as a rotatable shaft on which are. mounted a plurality of horizontally disposed blades, the action of which may be supplemented by baflles which project inwardly from the sides of the vessel; an orifice at the top for charging the vessel and a cover for sealing the same; an outlet at the bottom of the vessel for discharging the contents and a suitable valve for opening and closing the same; and a vapor outlet leading to a condenser,

furnished with a valve which may be opened or closed at will.

Four hundred pounds of finely divided colloided nitrocellulose in the form of a mud in which the individual particles are finer than 60 mesh, 4800 pounds of water, and 4 pounds of finely divided calcium carbonate were added to a vessel of the above type. This mixture was violently agitated by rotating the agitator at a suflicient rate so that the contents were in a turbulent state and the surface broken up into a number of vortices. While maintaining the agitation, the temperature of the mixture was raised to 50 C. by cirvariables in the opposite difor a period of 2 hours at culating hot water through the Jacket. Twelve hundred pounds of ethyl acetate containing 8 pounds of dinitrotoluene and 1 pound of dipbenylamine in solution were then added over a period of about 45 minutes while the violent agitation was maintained and the temperature was being raised to C. The vapor outlet 01' the vessel was then closed and the contents were heated rapidly to 75 C., the pressure rising to 12.5 pounds per square inch above atmospheric.

At this point the agitation was stopped and the mixture was allowed to separate into two layers, a bottom aqueous layer, and an upper layer of nitrocellulose-ethyl acetate lacquer containing droplets of water emulsified therein. During the stationary separation period of about 15 minutes, a solution of 14 pounds of gum arabic in 50 pounds of hot water was added to the vessel from a, pressure tank maintained at about 25 pounds per square inch pressure above atmospheric.

Violent agitation was then resumed and continued for a brief period, for example, about 4 or 5 minutes. This resulted in the separation of the lacquer into irregularly shaped particles, each of which was subsequently to be transformed-into a spherical grain of smokeless powder. In order to accomplish this transformation of irregular particles to globules, the mixture was maintained about '75 C. during agitation sufilcient to maintain the suspension in the freely swirling liquid while keeping the surface of the liquid smooth and unbroken.

During the grain shaping period, the density 0f-the resulting powder grains may be controlled in accordance with the process disclosed and claimed in U. S. Patent 2,160,626. For example, in order to increase the density of the product produced in accordance with the present example, a solution containing 75 pounds of sodium sulfate (calculated on the basis of anhydrous salt) in 400 pounds of water was added under pressure during the first 15 minutes of the grain shaping period..

When the grains had assumed globular form, the temperature of the suspension was reduced to C. and the excess pressure above atmospheric was relieved by opening the vapor line leading to the'condenser. At this temperature, the lacquer globules became "frozen" form due principally to the greatly increased viscosity of the lacquer.

The solvent was then removed from the globules by a distillation process in which the temperature was gradually increased, for example, according to a schedule in which the temperature'was raised to C. in 45 minutes, then maintained during successive one hour periods at 65-70 C.,'at -75 C., and then at -87 0., and finally for minutes at 87-94 C. The water and,solvent vapor evolved from the suspension were caused to pass at atmospheric pressure through a condenser, the recovered solvent being suitable for reuse in the process After removal of the solvent as above described, the suspension was cooled to room temperature, the powder grains were recovered by filtration or by means of a centrifuge and washed with warm water in order to remove the protective colloid and salt. The grains could then be subjected to a screening operation forseparating the over-sized and under-sized grains from the product. The globular grains of gelatinized nitrocellulose resulting from this procedure had a gravimetric density of 0.837 and a majority globules in I in their acquiredf the grains were between 012-024 inch in diameter.

The powder grains at this stage may be subjected to any further desired processing step, for example, to a surface treatment with a modifying agent such as an accelerator and/or a deterrent. After drying and graphiting, the powder grains may be stored ready for use.

When a final product having different characteristics is desired, the manufacturing procedure may be varied from the above in order to secure greatest economy of operation. For example, in the production of spherical grains having an averagediameter of 0.01 inch, more rapid agitation may be employed and a grain shaping period of 30 minutes followed by a distillation period of 3-4 hours yield excellent results.

The relatively high fluidity of the lacquer of the smokeless powder base at the elevated temperature of the graining step causes the transformation of the dispersed particles of lacquer into globular shape to occur quite readily, while the increased viscosity of the lacquer at the lower temperature provided after the graining step imparts to the globules a marked resistance to deformation during the unavoidable collisions with other globules, with the agitating means, and with the walls of the vessel incident to agitation during the step of removing the solvent.

As illustrating a further embodiment of the invention wherein reduction of pressure upon the mixture after the globules have been formed is accomplished without chilling but by venting the sealed vessel containing pounds of fibrous wood nitrocellulose (containing 13.4% nitrogen) and 41 pounds of finely divided chalk are suspended in 26,000 pounds of water and the resulting suspension, after being heated to a temperature of 50-55 C., is

pumped into the distillation vessel. 10,400 pounds of ethyl acetate, containing 33 pounds diphenylamine, are then added to the suspension during agitation. The suspension is then heated 'to a temperature of 80 C. in about 45 minutes, the vessel being sealed so that a pressure of about 15 to 20 pounds per square inch above atmospheric is developed, depending upon the amount of air which is present.

The agitation is discontinued for a period of about 15 minutes, permitting the nitrocellulose solution to coalesce as a separate layer above the water. During this time, a protective colloid solution is added, for example a solution of 120 pounds of a good grade animal bone glue in 1500 pounds of water.

Agitation is then resumed, and 15 minutes later a solution of 475 pounds of sodium sulfate in 1500 pounds of water is added. After a total of about 2 hours agitation at 80 C., the graining and shaping of globules is completed.

While the temperature is maintained at 80 C., the outlet valve to the condenser is gradually opened until a decrease in pressure is noted on the pressure gauge. The pressure decreases to about 5 pounds per square inch gauge in about to minutes, venting of air accounting for most of this pressure drop. The distillation of solvent starts at this point and continues for a period of about .60 minutes, the pressure in the distillation vessel being reduced gradually to atmospheric by further opening the outlet valve to the condenser at intervals. About 80% of the solvent is removed during this time.

While the above described gradual decrease of pressure can beaccomplished by careful inch in diameter and 12% being larger than i s the solvent.

the mixture, 3300 manual operation of the outlet valve, it is generally preferable to provide automatic pressure release according to a predetermined schedule.

The. temperature of the suspension is then raised to about C. in 45 minutes and maintained at this point for about 15 minutes to complete the solvent removal treatment. After cooling, the charge maybe centrifuged, washed, and screened and subjected to any other finishing treatment that may be desired.

The product of the foregoing process consists of globular grains of gelatinized nitrocellulose, displaying a gravimetric density of .930 and of which about 74% have a diameter between 0.010 and 0.025 inch, 14% being smaller than 0.010

0.025' inch in diameter. a

In the manufacture of globular smokeless powder grains, in accordance with the present invention economy is secured not only by virtue of the reduction in the amount of solvent required but also because a shorter period is required for forming the grains and for removing Likewise, the rate of solvent removal may be much higher than for globules which contain a much higher proportion of solvent, since due to the reduced shrinkage obtained on removing solvent from globules which initially contain a high solids content, there is less danger of deforming the grains by shrinkage thereof. The process of this invention, due to the latter factor, is particularly suited for the production of dense grains.

It will be understood tha an important aspect of my improved process is the carrying out of the step of graining, or globule formation, at

pressures substantially above'atmospheric which makes it possible to utilize temperatures sufllciently high that the heat contributes toward increasing the fluidity of the lacquer, without, however, depleting'the lacquer of solvent. The graining step is followed by lowering of the pressure, whichmay or may not be attended by a lowering in temperature, in order to set the grains in their acquired form, and finally, the residual volatile solvent may be substantially removed, as by evaporation. The operating details hereinbefore described are to be considered as illustrative of the invention and not limitative, and many variations may be made within its spirit and scope as will be realized by those skilled in the art when the present description is read. Such variations may include, for example, the utilization of other smokeless powder bases, other solvents, and other suspension media, as hereinbefore described, as well as changes in the temperatures, concentrations, and times of treatment which are subject to adjustment to give the most desirable results in each particular instance.

Having now described the invention, what is claimed as new and is desired to be secured by Letters Patent, is:

1. In the art of making explosives, the process comprising, agitating nitrocellulose and 1 to 4 times its weight of a water-immiscible solvent therefor in an aqueous bath, heating the mixture to 70-85 C. during agitation without removal oi solvent to form a suspension of fluid particles oi nitrocellulose solution, continuing the agitation under the said conditions to form the said particles into globular shape, and cooling the suspension to about 60 C. to rigidify the said globules.

2. In the art of making explosives, the proces: comprising, suspending particles of smokeles:

powder base solution in a non-solvent liquid at an elevated temperature sufficiently high to render the solution fluid, said non-solvent liquid being substantially immiscible with the solution agitating the suspension while avoiding the removal of solvent from the solution to form globules thereof, then cooling the suspension to rigidify the said globules, and thereafter removing solvent.

3. In the art of making explosives, the process comprising, agitating a smokeless powder base in a non-solvent liquid with solvent which is immiscible with and has a lower boiling point than 7 comprising, agitating a. smokeless powder base in a non-solvent liquid, adding solvent substantially immiscible with the liquid in an amount insufi- Q cient to render the said base fluid at the temperature of admixture but sufficient therefor at a higher temperature, heating the mixture to the said higher temperature while concurrently com- ,porting th temperature and pressure of themixture with the vapor pressure of the solvent to substantially avoid removal of solvent from the solution, continuing the agitation under the said conditions to form globules of the solution, and then cooling the suspension to rigidify the said globules.

5. In the art of making xplosives, the process comprising, agitating a smokeless powder base in a non-solvent liquid with solvent which is immiscible with and has a lower boiling point than the liquid, the solvent being insuficient in amount to render the said base fluid at below the boiling point of the mixture but suflicient therefor at a higher temperature, heating the mixture in a sealed vessel, to above the normal boiling point of the mixture, continuing the agitation under the said conditions to form globules of smokeless powder base solution, and then cooling the suspension below the boiling point of the mixture to rigidify the said globules,

6. In th art of making explosives, the process comprising, agitating a smokeless powder base in a non-solvent liquid with solvent which is immiscible with and has a lower boiling point than the liquid, the solvent being sufiicient in amount to render the said base fluid at a temperature above the boiling point of the mixture, heating the mixture in a sealed vesse to the said temperature and to a pressure above atmospheric, continuing the agitation under the said conditions to form globules of smokeless powder base solution, and thereafter removing solvent at atmospheric pressure.

7. The process. of claim 2, in which the smoke.- less powder base consists of nitrocellulose.

8. The process of claim 2, in which the smokeless powder base consists of nitrocellulose-nitroglycerin.

9. The process of claim 2, in which the smokeless powder base consists of nitrostarch.

10. In the art of making explosives, the process comprising, agitating nitrocellulose and about three times its weight of a water-immiscible sol vent in an aqueous bath, heating the mixture to substantially 75 C. during agitation to form a suspension of fluid particles of nitrocellulose solution, continuing the agitation under the said conditions to form globules of the solution, concurrently with said heating and agitation comporting the temperature and pressure of the mixture with the vapor pressure of the solvent to substantially avoid removal of solvent and cooling the suspension to about60 C. to rigidity the said globules.

11. In the art of making explosives, the process comprising, agitating a smokeless powder base in a non-solvent liquid with solvent which is immiscible with the liquid, the solvent being insufllcient in amount to render the said base fluid at an intermediate temperature above atmospheric but suflicient therefor at a higher temperature, heat ing the mixture to the said higher temperature,

continuing .the agitation under the said conditions to form globules of the solution, concurrently with said heating and agitation comporting the temperature and pressure of the mixture with the vapor pressure of'the solvent to substantially avoid removal of solvent and then cooling the suspension to the said intermediate temperature to rigidify the said globules.

12. Iii the art of making explosives, the process comprising, agitating a solution of smokeless powder base in a non-solvent liquid, the solvent for saidsolution being immiscible with the liquid, the solvent being sufllcient in amount to;

render the said base fluid at a temperature above the normal boiling point of the mixture, heating the mixture in a sealed vessel with concomitant increase in pressure to a temperature above the normal boiling point of the mixture, continuing the agitation under said conditions to form globules of smokeless powder base solution, then reducing the pressure in the vessel while agitation continues.

13. In the art of making explosives, the process comprising, agitating a solution of smokeless powder Jase in a non-solvent liquid the solvent for said solution being immiscible with andhaving a lower boiling point than the liquid, the

solvent being suflicient in amount to render the said base fluid at a temperature above the atmospheric pressure boiling point of the mixture, heating the mixtur in a sealed vessel with concomitant increase in pressure to a temperature above the boiling point of the mixture at atmospheric pressure, continuing the agitation under said conditions to form globules of smokeless powder base solution, then reducing the pressure in the vessel while agitation continues, and thereafter under reduced pressure distilling solvent from the mixture.

14. In the art of making explosives, the process comprising, agitating a solution of smokeless powder base in a non-solvent liquid, the solvent for said solution being immiscible with and having a lower boiling pointv than the liquid, the solvent being suflicient in amount to render the said base fluid at a temperature above the atanon-solvent liquidwith solvent which is immisto render cible with and has a lower boiling p int than the liquid, the solvent being suflicient i amount ilcient in amountto render said base fluid at atmospheric temperatures, heating .the mixture under pressure above atmospheric to a temper-- ature above the atmospheric pressure: boiling point of the mixture, continuing the agitation under the said conditions toform globules or smokeless powder base solution, and thereafter,

under reduced pressure, distilling solvent'from ;the mixture. v a V v 16. In the art of making explosives, the proc-' the said base, fluid at a temperature above the boiling point of the mixture, but insu'I- can comprising, agitating nitrocellulose powder in a bath of water with ethyl acetate there beingapproximately 3 to 4 parts, by weight,

.oi ethyl acetate to each part 01' base powder, concurrently agitating and heating the mixture in a sealed vessel to atemperature of about 80 C. with concomitant increase in pressur'e to about 15 .to 20 pounds per squareinchabove atmospheric pressure, without reducing the temperature ancipiessure discontinuing the agitation for a time sufllcient to permit the base powder solution to coalesce, resuming the agitation and continuing the same until the smokeless powder base solution is dispersed as globules in the water, all without reducing the temperature or pressure upon'the mixture, then gradually reducing the pressure within the vessel to vbetween zero and 5 pounds per square inch above atmospheric while maintaining the temperature,

and continuing the heating at such reduced pressure-until the ethyl acetate is substantially removed from the globules. v r g 17. In the art oi making explosives, theprocess comprising, suspending particles of smokeless powder base. solution in a non-solvent liquid at an elevated temperature above the normal boiling point or the mixture to render the solution fluid,said non-solvent liquid being substan-V tially immiscible with the solution agitating the suspension under pressure while avoiding the removal of solvent from the solution to form globules thereof, then reducing the pressure while agitation continues.

, CHARLES EARNEST SILK.