104 8cieniific Proceedings, Royal Dublin Society. 



The form in which the silver should be added depends on the 

 nature of the substance. If the substance consist mostly of 

 compounds of lead, bismuth, copper, arsenic, antimony or tin, 

 silver chloride should be employed, and should be mixed with the 

 substance and borax before the fusion. If, however, the substance 

 consist principally of difficultly reducible oxides or oxides of 

 nickel or zinc, then metallic silver, added after fusion, is best. 



In some cases the substance and fluxes were fused together in 

 a shallow cavity, using the oxidizing flame ; cooled, powdered in 

 an agate mortar, then mixed with silver chloride, and again fused. 

 This is v-ery troublesome, and the employment of the silver as wire 

 was found to give quite as good results. 



The sodium carbonate used was the ordinary dried and powdered 

 material. After a great number of experiments its employment 

 was discontinued, except when dealing with siliceous substances, as 

 no advantage seemed to attend its use with other bodies. 



Quantifies. — The most convenient quantities to work upon 

 generally are 3 decigrams of substance, and 12 decigrams of borax. 

 These quantities yield beads which can be easily worked before 

 the blowpipe in the necessary manner, in a cavity of the dimen- 

 sions given above. The proportion of borax may be varied within 

 reasonable limits (from 2 to 6 times the weight of substance taken) 

 without injuriously affecting the fusion. In dealing with a body 

 containing very large proportions of nickel or zinc, not more than 

 1 decigram of the substance should be taken. 



While the fusion is proceeding, the charge must be worked 

 round and round the cavity, the metal bead being made to run 

 round the glass, and pick up the metals as reduced. When 

 finished the whole charge may be allowed to sink to the bottom of 

 the cavity, the metal bead being under the glass. This somewhat 

 protects the metals from oxidization. 



The fusion must be cooled most carefully in an atmosphere of 

 coal gas (by directing a stream of gas into the cavity), as other- 

 wise some easily oxidizable metals may become oxidized. This is 

 especially necessary when arsenic, lead, bismuth, tin, or zinc are 

 present. 



We found that the compounds of nickel, cobalt, iron, zinc, and 

 tin, with phosphoric acid and silicic acid, behave before the blow-pipe 

 in a similar manner to the salts of these metals with volatile acids. 



