COAL ANALYSIS. 23 



ash. with some sodium carbonate and 0.2 grams of sodium ni- 

 trate : more nitrate than this attacks the platinum crucible. 

 Dissolve the fused mass in water, acidify, and evaporate to 

 dryness. Take up with hydrochloric acid and determine the 

 phosphorous by weighing the yellow precipitate of phospho- 

 dodecamolybdate of ammonium obtained in the usual way. 

 As a check on the purity of the yellow precipitate, the phos- 

 phorous in the combined duplicates may be determined by the 

 magnesia method. 



Nitrogen. KjeldahPs method is the simplest and best 

 Take one gram of powdered coal and place it in an Erlen- 

 nieyer's flask with two grams of dried sulphate of copper and 

 20 c.c. of concentrated sulphuric acid, place a loose cover on 

 top of flask and heat over a Buiisen burner for about half an 

 hour, or till all frothing ceases. Then add 10 grin, sulphate 

 of potash and heat strongly till no unoxidised black particles 

 of coal remain, and the solution is clear. Cool and add water. 

 Close the neck of the flask with a cork in which there are two 

 holes, one for a thistle funnel which reaches to the bottom, the 

 other for a distilling bulb. The outer tube from the latter 

 is connected with a condenser which leads just under a known 

 quantity of deci-normal sulphuric acid contained in a flask. 

 Strong caustic soda solution is poured down the thistle 

 funnel till the contents of the flask is alkaline. Then distil 

 for about an hour; add hot water down the thistle funnel to 

 make up loss and distil for another half hour, by which 

 time all the ammonia will have been driven off and taken up 

 by the sulphuric acid in the receiving flask. Use a drop or 

 two of methyl orange in the deci-normal sulphuric acid as an 

 indicator, for should the red colour change to yellow, thereby 

 indicating that there is not sufficient acid present, there will 

 be a loss of ammonia, thus making the analysis incorrect. 

 When the distillation is complete, the quantity of residual acid 

 is determined with standard ammonia. Each cubic centimetre 

 of the deci-normal sulphuric acid used up is equal to 0.0014 

 grin, nitrogen. 



The ultimate analysis, which gives the percentages of the 

 elements of which the coal is composed, does not convey all 

 the information we require, so we have to fall back on the 

 proximate analysis, which gives us the percentage of moisture, 

 volatile hydrocarbons, fixed carbon, ash and coke. The 

 specific gravity, calorific power and other useful it-ems may 

 also be supplied, which give a good idea of the general adapta- 

 bilities of a coal. 



Proximate Analysis. 



Moisture. Weigh out 1 gram as quickly as possible into 

 a porcelain crucible, place in a double-walled air bath and dry 

 for an hour, the bath being kept at a temperature as near to 



