CHEMISTRY. 417 



into the original beaker, and boil the i^recipitate a few minutes with about 150 to 200 

 t;c. water containing a little pure ammonium chlorid or nitrate. The boiling should 

 be continued only 2 or 3 minutes, otherwise the precipitate does not settle well. 

 As soon as it has settled, pass the supernatant liquid through a new filter, using this 

 time a pump and cone. Repeat the boiling and decantation once or twice, transfer 

 the precipitate to the filter, and wash several times with hot water. Suck dry and 

 transfer to a covered crucible, which has been weighed. Dry carefully over the 

 flame, burn the paper, and heat from 5 to 10 minutes at the highest temj^erature 

 of the blast lamp. Cool from 10 to 15 minutes in a sulphuric acid desiccator, and 

 make an approximate weighing. Heat again for 5 minutes, cool as before, and 

 weigh as directed. From the weight of the precipitate subtract the weight of the 

 impurities in the potash." 



A study of the conditions affecting the accuracy of the method is 

 reported. 



Estimation of calcium carbonate in soil, H. ScHtJTTE {Ztschr. 

 Angnr. Chrni., 1890. j>. HoJ^; ahs. in AnaJyst, 25 {1900), May,]). 132).— 

 It is claimed that the Stutzer and Hartleb method (E. S. R., 11, p. 110) 

 does not give accurate results when applied to some soils, especially 

 those poor in calcium carbonate and containing zeolites. Immendortt's 

 method, carried out as follows, is recommended: Extract the soil with 

 hot hydrochloric acid, make a portion of the solution alkaline with 

 ammonia, warm, clear up with a little acid, and boil. Add a large 

 excess of a strong solution of ammonium oxalate, boil for some time, 

 make alkaline with ammonia, and then faintly acid with acetic acid. 

 Determine the calcium oxalate by titration, or preferably (if the soil 

 contains much iron) collect it on a iilter, ignite, and weigh. 



Direct estimation of calcium in the presence of iron and alumi- 

 num, E. Blum {Zts<-hr. Analyt. Chem., 39 {1900), No. 3, pp. 162- 

 155). — This method is used in estimating calcium in iron ores and l)last- 

 f urnace slags. The calcium is precipitated by ammonium oxalate, the 

 iron and aluminum being* held in solution by the presence of tartaric 

 acid added to the ammoniacal solution. By this procedure small 

 amounts of oxids of iron, aluminuu), and manganese are carried down 

 with the calcium oxalate, but this is said to be very nearly compen- 

 sated by the calcium that is not precipitated. This is a ver}^ short and 

 practical method, but can not l)e used with substances containing more 

 than 0.5 per cent of manganese. — c. b. williams. 



Soil humus — some sources of error in analytical methods, A. L. 

 Emery {Jour. Amer. Chein. Soc.,22 {1900), No. 5, pp. 285-291).— Thvae 

 sources of error are discussed, namely, the expulsion of ammonia from 

 organic matter during leaching with caustic potash, the absorption of 

 ammonia by the humus extract when the soil is leached with ammonia 

 solution, and the loss of organic matter in washing with hydrochloric 

 acid to remove lime. The author proposes to overcome the first diffi- 

 culty by the following means: "The soil to be leached with caustic 

 potash is placed in a funnel which is closed at the top with a stopper 

 through which the leaching solution is admitted by a separatory funnel. 



