An Attempt to analyse Cast Iron. 24§ 



that all substances soluble by ati acid ought to have been 

 taken up; vet I found, alter ignition of the undissolved 

 mass, a portion of magnesia, which irequently amounted to 

 the whole of what was contained in the iron, and which 

 is never left undissolved when sulphuric or muriatic acids 

 are employed without anv addition of nitric acid. The 

 magnesia, or its base, must therefore have entered into the 

 composition of this substance, as is the case in vegetables, 

 from which the various earths met with in the ashesnever 

 can be separated by acids before combustion. 



1. A piece of cast iron (part of the same mass that was 

 employed for all the analy.-es hereafter described) weighing 

 19' 1 grammes, was dissolved in a mixture of sulphuric acid, 

 nitric acid, and water. The dark-brown solution jiroduced 

 was strained through'a weighicd filter, and the black-brown 

 mass left on the liltcr was first washed with water and 

 nitric acid, to remove all the iron, and then with boiling 

 water. That which passed throua;h during the washing 

 with boilinii water deposited a brov\ n substance on cooling. 

 The dried filter had gained i!25 of a gramme of adherent 

 brown extractive substance, of which 0-15 could be taken 

 from the filler without injininsj the paper: this when burnt 

 letl 008 of a gramme of grav-red ashes corresponding to 

 045 for the 0'225 of extractive substance. These ashes 

 when boiled with muriatic acid left 0-025 of sihca, equal 

 to 0-037 for the whole mass. Out of the solution sa- 

 turated with caustic ammonia was precipitated a vestige of 

 iron by benzoate of potash, after which carbonate of 

 potash separated, on boiling, a small quantity of magnesia, 

 but too dnninutive to be weighed. (Here it might be 

 asked, how the nature of a substance can be ascertained 

 when in so small a quantity as not to be weighed ? 1 had 

 had an opportunity of discovering this by an assay on a 

 larger scale. From 107 grammes of the very same kind of 

 cast iron, dissolved in a similar mixture of acids, I obtained 

 magnesia in such quantity, that its proportion to sulphuric 

 acid evidently disimguished it from lime and other kinds? 

 of earths. But as, in my experiments with the brown ex- 

 tractive mass, an indeterminable portion of its weight had 

 been destroyed, I could no*, even from this experiment on 

 a larger scale, determine the ejuantity of magnesia therein, 

 which at all events is extremely small.) That portiim of 

 the extractive substance which was found partly di^5solved 

 and partly precipitated in the water employed to wash the 

 filter, weighed, after drying, o* I 7 of a granmie, and produced 

 001 7 of ashes in characler like the former. These ashe« 



(0*043 + 



