Gelatin Lead Azide

Animal gelatin can be used for crystal modification and desensitization of lead azide in a manner similar to dextrin. A product recently described by 

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The presence of dextrin in the solution favours the precipitation of tiny, equal sized, rounded crystals. In Fig. 47 magnified crystals of dextrinated lead azide are shown and in Fig. 48 crystals of ordinary lead azide are shown for comparison. According to Sudo [96] gelatine exerts an influence similar to that of dextrin. In this author s opinion when precipitated from a solution containing gelatine lead azide is less sensitive to friction than that from solutions without added colloids. 

Gelatine Lead Azide (GAM)> Animal gelatine was used for crystal modification of lead azide with the addition of a small amount of molybdenum sulphate [132]. It is claimed that the product is safer in handling than usual lead azide. 

Figure 15, Gelatin lead azide (GAM) sectioned crystal agglomerate showing concentration of molybdenum disulfide in inner part of lobes, 308x. (Photo courtesy of ICI, Nobel s Explosives Company Ltd., Stevenston, U.K.)...

Many other methods of making lead azide in a safe form have been described, but the only one to have found commercial importance consists of replacing the dextrine by a small proportion of gelatine. When properly made this form of lead azide is as safe to handle as the dextrinated form and has improved sensitiveness to flame. It can therefore be used by itself in electric and delay detonators, but not in plain detonators as it is not ignited with certainty by safety fuse. 

The normal initiating charge in a British detonator is lead azide modified with gelatine. In the case of plain detonators a small proportion of lead styphnate is added to the azide to ensure satisfactory ignition from safety fuse. 

Black Powder 225 to 300, NC (13%N) 185, smokeless powder 185, NG 160, Nitrostarch 170, NH4N03 225, Tetryl 190, Mercury Azide 200, Silver Azide 200, Lead Azide 340 to 350, Cuprous Azide 210 to 350, Cupric Azide 245, Mercuric Fulminate 160 to 200, Silver Fulminate 200, Chedaite 200, blasting gelatin 207 to 211 and Picric Acid 225 to 350°... 

Gelatin, azide, molybdenum disulfide (GAM) form of lead azide GAM was... 

Bryan and Noonan [98] carried out similar investigations using helium and estimated the minimum energy required to ignite lead azide with a 3 msec delay to be 0.087 cal/cm2, i.e. less than that for blasting gelatine, 0.15cal/cm2, PETN, 0.25 cal/cm2 and tetryl, 0.33 cal/cm2. 

Fig. 48. Lead azide precipitated in different conditions, according to Sudo[96] (a)— from high concentration of lead acetate (10%) and low of sodium azide (4%) (b)— from low concentration of lead acetate (4%) and high of sodium azide (10%) (c)— from low concentrations of lead acetate (4%) and sodium azide (2%) (d)—from high concentrations of lead acetate (25%) and sodium azide (10%) in the presence of gelatine (5%) (e)—from high concentrations of lead nitrate (25%) and sodium azide (10%) in the presence of gelatine (5%) (very small crystal form).

Silver NENA forms a chalky white solid, which decomposes when heated to 120 Celsius. It darkens on exposure to light, and should be stored in amber glass bottles in a refrigerator. Silver NENA is used in blasting caps as a substitute for lead azide, diazodinitrophenol, or lead styphnate. It has applications for use in priming mixtures as a substitute for mercury fulminate or sulfur nitride, or admixed with sulfur nitride. Silver NENA should be desensitized by mixing with dextrose, starch, pectin, gelatin, or paraffins. 

L. E. Medlock, J. P. Leslie, Some Aspects of the Preparation and Characteristics of Lead Azide Precipitated in the Presence of Gelatin. Paper No. 10, Int. Conf. Res. Primary Explos., Explosives Research Development Establishment, Waltham Abbey, Essex, England, 17-19 March (1975). 

Medlock, L.E., Leslie, J.P. Some aspects of the preparation and characteristics of lead azide precipitated in the presence of gelatin. In Jenkms, J.M., White, J.R. (eds.) Proceedings of the International Conference on Research in Primary Explosives, vol. 2, pp. 10/1-10/16, Waltham Abbey (1975)... 

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