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go off in the hand, when carrying from oneplace to another, fo that in faft when it is oncedry, the operator fhould be prepared for theexplolion at any time, even with the moft care-ful handling. A momentary flalh is vifible atthe time. If the ammoniacal fohition pouredoff from the fulminating cryftals is heated in afmall retort (which however is a moft hazardousexperiment) bubbles of azotic gas are given out,and fmall opake cryftals with a metallic fplen-dour are formed,.which fulminate violently whentouched, even in the midft of the liquor, andthe veilel burfts into an infinite number of frag-ments. When any of this folution touches theIkin it blackens it for a time like nitrat of filver.The fulminating cryftals when dry, appear toremain unaltered for a confiderable time, forFourcroy relates that he has feen them explodewith their ufual violence, after being kept forfome months undifturbed.

It appears probable that there are two or threevarieties of this ammoniacal oxyd of filver,fuch as, the black powder which fubfides atfirft when lefs ammonia is added to the oxydof filver than will difTolve it, the fulminatingcryftalline pellicle which firft feparates fromthe folution, and the black cryftals which fepa-rate when the folution is boiled. The firft ofthefe, the black powder, is ftated by Dr. Hig-gins not to have a fulminating property, but theprecife nature of thefe compounds has been butlittle examined.

It requires confiderable care to fucceed inproducing the fulminating filver. The metalfhould be quite free from copper, the oxyd pro-duced by lime fhould be thoroughly edulco-rated, and efpeciali'y the ammonia fhould hequite free from carbonic acid. Carbonat ofammonia does indeed diffolve the oxyd of filverwith fome effervefcence, owing to the efcape ofpart of the carbonic acid, but with the remaindera triple ammoniaco carbonated oxyd of filver, isformed, which will not fulminate.

Several ferious accidents have happened inpreparing this fulminating filver which fhewthe neceffity of great precaution in the opera-tor, and as all the cifcumftances in which tlieexplofion is produced are not as yet known,he fhould on no account venture to preparemore than a few grains at a time of this dan-gerous compound. Dr. Higgins mixed toge-ther 24 grains pf the oxyd of filver with aquarter of an ounce of water Jaturated withammoniacal gas in a corked bottle, which pro-duced a blue folution with the expulfion of

* Tom. 3S, p. 363, 1

fome gas, and without the formation of anypellicle, and fix hours afterwards, on fhakingthe bottle to compleat the folution of a littleblackened oxyd which lay at the bottom, thewhole exploded with exceffive violence, thebottle was quite reduced to powder, and'hishand was numbed as if' with the blow of aheavy hammer. In this cafe it appears probablethat this unexpected explofion arofe, partlyfrom ufing too concentrated a folution of am-monia, too large a quantity of filver, and ef-pecially from fhaking the contents of the bot-tle. Another accident is mentioned in theJournal de Phyfique 1 where the preparationleems to have been condufted with perfeftprudence and accuracy, and an ammoniacal fo-lution was made, which contained apparentlyabout five grains of the fulminating cryftals,but on dipping a card into it to take out thecryftals, the whole exploded with exceffiveviolence, which had nearly deprived the opera-tor of his fight. The only difference from thecommon way of operating in this cafe ap-peared to be that the cryftals were allowed toremain in the folution twenty-four hours aftermixture, inftead of being taken out as foon asthey appeared.

It has been already mentioned that this ful-minating filver is alfo produced when muriatof filver is boiled with pure ammonia, and: ex-plodes in the aft of formation, and hence arifesanother precaution in applying artificial heatto any mixture of ammonia and oxyd of filverfree from carbonic gas.

Silver is capable of uniting with fulphur invarious proportions. Artificial fulphurettedfilver is a black brittle mafs, like the native ful-phuret. The utmoft proportion of fulphurcapable of uniting with filver is ftated' byWenzel 11 to be 13 of the former to 87 of themetal. Yet the following experiment by thelate Mr. Alchorne, feems to fhew that the fil-ver does not eafily retain much more than halfthis quantity at a moderate red heat. Half anounce (240 grains) of filver precipitated fromthe nitrat by copper was mixed with its ownweight of fulphur, and put into a crucible withanother, inverted over it, and luted, leaving afinal L hole for the efcape of the fiiperfluousfulphur.. On applying a red heat, part of thefulphur efcaped and burned off at the hole; Thefire was increafed' to a degree which wasjudged fufficient to melt the mafs within, andkept up till the blue flame difappeared. Whencold, a dark lead-coloured brittle button w«Kir,van’s Miniralojy, vel. 3.