50 THE TESTING <>F KoAD MATERIALS. 



DETERMINATION. 



One hundred cubic centimeters of solution A is put into an Krlenmeyer tlask, 

 made slightly alkaline With ammonia and then again acidified with nitric acid. About 

 10 grains of dry ammonium nitrate is added and the solution heated lo (>0 C. 

 Twenty-live cubic centimeters of the molybdate solution is then poured into the 

 flask, a smooth, tightly fitting rubber stopper inserted, and the contents of the flask 

 vigorously shaken for five minutes. After allowing a short time for the yellow 

 precipitate to settle it is filtered and washed five or six times with a 3 per cent solu- 

 tion of potassium nitrate. The precipitate and filter is transferred to a beaker, dis- 

 solved in a small excess of standard alkali, a few drops of phenolphthalein added, 

 and the solution titrated with the standard nitric acid. 



LIME. 



The concentrated filtrate from the iron, alumina, etc., is made decidedly ainmo- 

 niacal and brought to a boil, a sufficient quantity of saturated solution of ammonium 

 oxalate is then added, avoiding a large excess. Boiling is continued for a few min- 

 utes when the beaker is immediately set into a dish of cold water. The precipitate 

 settles rapidly, and is at once filtered, using a platinum cone with the pump, and 

 washed thoroughly with hot water. The filtrate is reserved for the determination of 

 the magnesia. The filter paper containing the washed calcic oxalate is lifted fron 

 the cone and opened inside a beaker. By means of a well-directed stream of a wash 

 bottle all precipitate can be washed off the paper. Fifty cubic centimeters of dilute 

 sulphuric acid is then allowed to run over the paper into the beaker, more water is 

 added, the solution heated to about 60 C., and immediately titrated with standard 

 permanganate solution. The lime factor is exactly one-half the iron factor of the 

 permanganate solution. 



MAGNESIA. 



The filtrate from the lime determination is made slightly acid with hydrochloric 

 acid and 30 cc of a concentrated solution of disodic phosphate added. It is then 

 evaporated down to a bulk not exceeding 150 cc, transferred to an Erlenmeyer flask, 

 and after cooling ammonia is added gradually with shaking until the reaction is 

 strongly alkaline. The flask is stoppered with a smooth rubber stopper and shaken 

 vigorously for five minutes. r,y this treatment the precipitate will usually be ready 

 to filter inside of an hour. The filtrate should always, however, be preserved ovi r 

 night to make sure that no more precipitate appeal's. The precipitate is collected 

 either on paper or a weighed < iooch crucible, burned, blasted, and weighed a< mag- 

 nesium pyn>- phosphate (Mj P () I, which multiplied by 0. ."><'>!!) equals magnesium 

 oxid (MgO). 



A< n>. 



Sulphur occurs in rock and clays usually as snlphids, more rarely as sulphates. 

 The quantities are nearly always small, and in the cases where they are not the 

 microscopic examination has disclosed the fact. It is customary in rock and day 

 analysis to report sulphur as S< >,. and that method has been followed. 



The remaining 100 CC of Solution A is heated to boiling, and a few cu! lie cent iii i' 

 of a solution of barium chlorid added, arid the boiling continued for five minutes. 

 When the precipitate is settled it i< collected on a paper or on a weighed Gooch 

 crucible, washed with hot water, ignited, and weighed as barium sulphate (\\-.\- 

 which multiplied by <>.:;j:;i) equals s< > . 



KKKK-OI - [EON. 



The determination of iron in the ferrous state is an important matter in connection 

 with the analysis of clays. Fairly satisfactory determinations can be secured by boil- 



