706 GEOLOGY AND MINING INDUSTRY OF LBADVILLB. 



No. XXX is the slag, in distinct detached crystals, from the La Plata smelter, 

 which has already been described in the reactions of slags. No. XXXI is a sample of 

 so called acid slag from Gumming & Finn's smelter. This sample was made of 124 

 pieces of slag, each piece representing the day's work of one furnace and specimens 

 from four furnaces being mixed together. 



No. XXXII is a slag of the singulo-silicate type, taken from the heap at Messrs. 

 Billing & Eilers's smelter. These three specimens have already been described in the 

 investigation on the properties of slags. 



Discussion A glance at the analyses shows: 



1. That the quantity of lead is in an inverse ratio to the quantity of lime and 

 magnesia existing in the state of silicates. 



2. That there is no relation whatever between the quantities of lead and of silver 

 left in the slag. This was shown also in the assays of slags from various sources 

 already given. It is rendered very apparent in an assay of another slag fijom Billing 

 & Eilers's smelter exactly similar to No. XXXII, which was examined very carefully 

 by the wet way for lead and assayed for silver. It contained 2.95 per cent, of lead 

 and 0.5833 ounce of silver, while No. XXXII contains lead, 3.07 per cent. ; silver, 

 1.639 ounces. 



This can scarcely be otherwise since lead exists in the slag in the state of combi- 

 nation and silver in the state of mixture. 



None of the slags analyzed contains any baryta, but, as this substance has been 

 found in some of the lead fumes condensed in the dust-chambers, it must be inferred 

 that some of the Leadville slags contain baryta. 



The slags were examined for chromium, tungsten, and vanadium, but the presence 

 of these metals could not be detected. 



Titanic acid could not be detected by the classical methods. The process used 

 with success for its detection and estimation was the following: The slag is dissolved 

 in a mixture of hydrofluoric, hydrochloric, and sulphuric acids, in a platinum vessel, 

 and the whole evaporated until sulphuric acid goes off in fumes (this to expel silica). 

 The product, dissolved in water, is treated by an excess of sulphtireted hydrogen to 

 precipitate any lead which might remain in solution. The solution is filtered and then 

 boiled for the expulsion of sulphureted hydrogen, and then brought as nearly as possible 

 to the neutral point by an alkali. Alumina and titanic acid are then precipitated by 

 hyposulphite of soda, and separated and estimated as usual. With the exception of the 

 preliminary operation needed for the preparation of the solution, the process is the 

 same as the one which has been recommended in the analysis of hematite. The quantity 

 of titanic acid in the hematite is insufficient to account for the relatively large propor- 

 tion of this acid in the slags. In all probability the oxide of iron of the lead ore con- 

 tains this substance, but some small quantities of titanate of lead may also exist in 

 the ore, although this mineral is not kuowu to exist. As has previously been stated, 

 the slags from the Little Chief smelter were examined very carefully and only doubtful 

 traces of titanic acid were detected. 



Careful experiments revealed the presence of carbon in the slag, but it is not 

 known yet in what state it occurs there. Two hypotheses are acceptable: either car- 

 bon exists in the state of graphite, a very easily mixed substance, and one which com- 

 bines, so to speak, crystallographically, as in cast iron, for instance, or else in the state 



