354 CONTRIBUTIONS TO BI,OWPIPE,ANALYSIS. 



be replaced by a glazed visiting-card. In examining earthy sulphates 

 by this method, a little borax ought always to be added to the car- 

 bonate of soda, in order to promote the solution of the test-matter. 

 If oxide of manganese be present in the ash, the well-known manganate 

 of soda, or " turquoise enamel," will also be obtained by this treat- 

 ment. 



Estimation of Sulphur : — The following plan is perhaps the most 

 simple that can be employed for the determination of sulphur in coal 

 samples. It is merely an adaptation to blowpipe practice of the pro- 

 cess very generally employed for that purpose : — 



As large an amount of coal as practicable, several pounds at least, 

 taken from different parts of the same heap or bed, must be broken 

 into powder and well stirred together. About 1 50 milligrammes are 

 to be weighed out for the assay. This amount is to be intimately mixed 

 with about 450 milligrammes of nitrate of potash and an equal quan- 

 tity of carbonate of potash, and the mixture, with a good covering of 

 salt, is to be fused in a small platinum crucible of about a quarter of an 

 ounce capacity. The crucible may be fixed in an ordinary blowpipe- 

 furnace, in the centre of an already used charcoal-block, as the cavity 

 of the latter will require to be larger than usual. The heat at first 

 must be very moderate, as the mixture swells up greatly ; but after a 

 couple of minutes, or thereabouts, a tolerably strong blast may be kept 

 up for from two to three minutes in addition, when the operation will 

 be finished. The alkaline sulphate, thus produced, is dissolved out by 

 boiling water, and the solution, acidified by a few drops of chlorhydric 

 acid, is then treated with chloride of barium. The weight of the pre- 

 cipitate divided by 7.28 gives the amount of sulphur. An ordinary 

 blowpipe crucible of. clay may be employed for this operation; but it is 

 always strongly attacked by the mixture during fusion, and is otherwise 

 less convenient for the purpose than one of platinum. 



When the iron pyrites in the coal is not in a state of semi-decom- 

 position, its amount, and consequently the amount of sulphur, may be 

 arrived at far more nearly than might at first thought be supposed, by 

 the simple process of washing in the agate mortar. Each single part of 

 pyrites corresponds to 0-533 of sulphur. Several large pieces of the 

 assay-coal should be taken, and broken up into powder, and a couple 

 of trials should be made on separate portions of this. About 500 

 milligrammes may be taken for each trial, and washed in three or four 

 portions. In the hands of one accustomed to the use of the mortar in 



