in the table gives the maximum variation in per cent, of this deviation at each temperature. This is a maximum at 0°and reaches a minimum of only 3% at about 30°. Further, kh at each temperature from 10 to 40°is a maximum at some salt concentration. Summary 1. From measurements of the cells without liquid junction,the thermodynamics of the hydrolytic reaction Ac -+ HiO HAc + OH~h as been studied from 0 to 40°and from 0 to 3 M sodium chloride concentration.2. Of the quantities in the equation of equilib-_ TDHTHAc OTQHOThAc _ 7ih^h 7ac0h,0 «A» rium Kh, 7h and kh have been evaluated. By this method the concentration term, kh, has been separated from the activity coefficient term, 7h• 3. Out results show that from 25 to 40°, inclusive, and from 0 to 3 M salt concentration, the total deviation from the mass action law is not greater than 4%.

Experimental velocity-diameter D(d) and velocity-density D ( p 1 ) curves are presented for 80/20 TNT-Aluminum (AI), 45/30/25 RDX-TNT-Aluminum (AI), 75/25 Composition B-AI (HBX), and various mixtures of ammonium nitrate and aluminum ranging from pure ammonium nitrate to 6OY0 AN. Also presented are some results with AN-DNT mixtures. Results show that aluminum reacts too rapidly for the energy release as a function of time to be a limiting factor in TNT-AI and RDX-TNT-AI mixtures at diameters above 5 cm., but it reacts relatively slowly in the AN-AI mixtures and the rate of reaction of aluminum (and AN), or the rate of energy release is a limiting factor in this case. The familiar pro erties of the high temperature Al-explosives are here attributed to the thermodynamics of AI-reactions in which the A128(g) /Al~Os(c) ratio is appreciable in the detonation wave but becomes negligible later on during adiabatic expansion. The change of this ratio from a high value in the detonation wave to an ultimate low value gives aluminized explosives low "brisance" but high blast potential. The AN-A1 mixtures were shown to be "non-ideal" (D < D*) over the entire range of conditions studied.Reaction rates in these mixtures are shown to depend on the particle size of both the AN atid the Al. They seem to be controlled by mass transfer which leads to anomalous D(p1) curves each showing a maximum at a relatively low density (1.0 to 1.2 g./cc.). IntroductionAluminized explosives are chayacterized in general by relatively low "brisance" but high (underwater, open air and underground) blast potential. The low relative I' brisance" of aluminized explosives has been attributed in the past to incomplete reaction of A1 a t the " Chapment-Jouguet plane," and the high blast-potential to after-burning of aluminum. Thus early unpublished shaped charge studies with aluminized explosives, interpreted in light of the observed linear variation with detonation pressure of hole depth and volume from jets in uniform targets indicated that aluminum acts effectively as a diluent as far as the end effect, e.g., shaped charge action, is concerned. More careful study showed, however, that aluminum lowers the "detonation" pressure and velocity even more, sometimes quite considerably more, than an ideal diluent. The effectively endothermic reaction of A1 in the detonation wave may be seen, for example, in the results of detonation pressure measuresummarized in Table I, by the shaped charge method (using calibration curves established with known ideal explosives). These data show that

Thermodynamics of Sodium Chloride Solutions 495 Hughes.20 The energy of activation for this reaction in solvents of constant dielectric constant appears to be "normal." However, the values reported in this paper are not sufficiently precise for use in testing modern theories. Summary Experimental velocity measurements have been made for the reactions of ethyl iodide with the solvent, sodium hydroxide, triethylamine, sodium acetate, and lithium nitrate in aqueous alcohol mixtures at 25 and 50°.Velocity constants have been calculated by (20) Moelwyn-Hughes, "Kinetics of Reactions in Solution,"

The formation of water-repellent films on solids by treatment in aqueous solutions of heteropolar substances involves some relatively liktle known surface chemistry of considerable theoretical interest. The most important industrial use of the phenomenon is in the separation of minerals by flotation. Heteropolar substances useful in this application, k n o w as "collectors," differ widely both in their solution characteristics (solubility, degree of ionization, surface activity) and in their modes of reaction at the solid surface. We believe, in fact, that water-repellent films on solids form not only by chemisorption or chemical reaction at the solid surface but also by physical adsorption, the latter type occurring commonly in the extremely capillary-active heteropolar compounds (long-chain paraffin salts, acids, and bases) (4). 17Tater-repellent film-forming compounds may be divided into three main groups: (a) anionic substances, Le., substances in which the active part of the molecule is the anion, (b) cationic substances, and ( c ) nonelectrolytes, listed in order of their industrial importance. The soluble nonelectrolytic collectors are also somewhat heteropolar and undoubtedly adsorb as whole molecules (examples are dixanthogen, aliphatic and aromatic sulfides and disulfides, and triphenylphosphine) ( 7 ) . We shall not be interested here in water-insoluble types. Under optimum conditions for selective conditioning of solids in flotation, anionic and cationic types exist in the (bulk) solution largely as ions. Typical anionic collectors are the xant,hates; these are k n o m to be nearly completely ionized in the (generally) basic flotation circuits. Alkylamine hydrochlorides are typical cationic collectors, and these are also largely dissociated into ions in the flotation pulp. Because of the strong electrolytic properties of these substances, proposed mechanisms for the formation of hydrophobic films by type (a) and type ( b ) collectors have generally been ionic in character. The various mechanisms that have been suggested for the "ionic" collectors are discussed comprehensively by Wark ( 2 3 ) .Recently, nn interesting controversy of neutral molecule adsorption us. ion exchange has arisen in the theory of anion-exchange resins. Bishop (2) accounted for the "ion-exchange" properties of Amberlite IR-3 on the basis of extraction of free acids of even such strong acids as hydrochloric rather than the exchange of anions at the surface. Schwartz, Edwards, and Bourdeaux (20), in studying ' Research Fellow. Utsh Engineering Esperinient Station, Salt Lake City, Utsli. S o w Senior Lecturer,

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