86 The Phosphates of America. 



manufacturers who contemplate the erection of an acid plant may 

 be briefly summed up in the following manner: 



(a) Of pyrites and brimstone, which is the most economical and 

 best source of sulphur? 



(b) If the preference be given to pyrites, what kind of furnace 

 or burner is best adapted for effecting its complete combustion, 

 including the "fines"? 



(c) What are the best dimensions to accord to the leaden cham- 

 bers in which are combined and condensed the gases induced by 

 this combustion ? 



(d) How may the maximum results be produced from the ore at 

 a minimum expenditure of nitrate of soda ? 



(e) How to dispose of the residual cinders after desulphuriza- 

 tion in order to lessen first cost. 



Of the first problem, the commercial aspect is the only part 

 with which we need to deal, for it is at last understood and, if 

 somewhat reluctantly, generally admitted, that from a pound of 

 sulphur, whether it be taken in the form of pure brimstone or in 

 combination with some mineral as a bisulphide, the same quantity 

 of sulphurous-acid gas, generated by its combustion, Avill be ob- 

 tained. 



From a purely scientific and theoretical point of view, and speak- 

 ing with that impartiality which we are called upon to observe, 

 there can be very little doubt that if all things were equal 

 there would be no room for hesitation in awarding immediate 

 preference to the cleaner, purer and in every way simpler brim- 

 stone ; and we must even go so far as to admit that inasmuch 

 as very few, if any, of the pyrites ores hitherto discovered and 

 worked are absolutely exempt from all traces of arsenic, there are 

 certain branches of chemical manufacture in which it would be 

 unadvisable, and others in which it would be in the highest degree 

 dangerous, to use them. These, however, call for the employment 

 of but a very insignificant quota of the gigantic total annually re- 

 quired for the great chemical fertilizer industry, in which a trace of 

 arsenic in the sulphuric acid employed is a matter of indifference. 



We may therefore leave the interests of small works where 

 only fine or medicinal chemicals are produced, or where only com- 

 paratively small quantities of acid are required, out of the ques- 

 tion. 



In comparing the relative cost of sulphuric acid derived from 

 brimstone or pyrites, it must be borne in mind that in the latter we 



