CHEMISTRY. 



95 



vert the nitrates into carbonates, he adds to 

 the soluble portion, after drying and weighing, 

 a little pure solution of sugar, evaporates to 

 dryness, and heats the platinum capsule gradu- 

 ally and by piecemeal with a very small gas- 

 flame, so that no deflagration may happen. 

 After prolonged but very gentle ignition, the 

 sugar-charcoal is found burned away, when 

 the residue is moistened with water containing 

 carbonic acid, and weighed again after drying. 

 The loss of weight in this case expresses the 

 weight of the organic substances and the dif- 

 ference between the equivalent of the nitric 

 acid which was present and of the carbonic 

 acid which has taken its place. This difference 

 can be easily calculated from the quantity of 

 the nitrates as previously ascertained, and must 

 be deducted. This process is not absolutely 

 accurate, but Herr Wagner considers it more 

 certain than others. Herr "Wagner calls atten- 

 tion to the necessity, in experiments for deter- 

 mining the solid residues, of protecting the 

 platinum or porcelain capsule in which the 

 water is treated against the accumulation of a 

 deposit from the gas-flame, through which a 

 liability to error in weight is incurred. For 

 this purpose he uses a thin sheet of platinum, 

 instead of the ordinary wire gauze, between 

 the capsule and the flame. 



Mr. Thomas Moore has published the follow- 

 ing new process for the separation of nickel 

 and cobalt from iron : Having removed any 

 excess of free acid by evaporation, and dis- 

 solving the residue in water, add to the solu- 

 tion a sufficient quantity of ammonic sulphate 

 to form a double sulphate with the nickel and 

 cobalt present. Dilute to about 150 c. c., and 

 add a rather large excess of oxalic acid, and 

 stir well. In case a precipitate form, more 

 ammonic sulphate should be added until a 

 clear solution is obtained. Add ammonic hy- 

 droxide in considerable excess; stir, heat 

 gently for a few minutes, and filter; wash 

 well with water containing ammonia; or di- 

 lute to about 500 c. c., and, after allowing the 

 precipitate to settle, withdraw a given portion 

 of the clear upper stratum of liquid. This, 

 after a further addition of ammonic sulphate, 

 to lessen the resistance to the electric current, 

 is ready for electrolysis or any other method 

 of estimating the nickel or cobalt. 



Messrs. R. H. Chittenden and II. H. Donald- 

 son, of the Sheffield Laboratory, Yale College, 

 describe a process for the detection and de- 

 termination of arsenic in organic bodies, which 

 they recommend as very accurate, delicate, and 

 simple. It is based upon Gauthier's process, 

 and somewhat resembles it, but requires for 

 reagents only nitric acid, sulphuric acid, and 

 zinc. The organic matter is destroyed by 

 successive oxidations with nitric and sulphuric 

 acids, as in Gauthier's method, but at a much 

 lower temperature. The suspected matter is 

 then treated for fifteen minutes at 200 C., and 

 allowed to cool, when a hard, carbonaceous 

 residue, free from nitric acid, and containing 



the arsenic as arsenious acid, is formed. This 

 is extracted with water till it has been made 

 to give up its arsenic, and the reddish-brown 

 fluid containing some organic matter is evap- 

 orated to dryness. The residue is dissolved at 

 a gentle heat with a definite quantity of dilute 

 sulphuric acid, and introduced to a Marsh's ap- 

 paratus for the decomposition of arseniuretted 

 hydrogen by artificial heat, to which a Bun- 

 sen wash-bottle and a device for graduating! 

 the admission of the fluid have been added. 

 The resultant gas having been dried in a 

 chloride of calcium tube, is passed through a 

 red-hot glass tube. Not a trace of arsenic 

 passes by if the cooled tube is of proper 

 length. The apparatus is then filled with 

 hydrogen generated by the sulphuric acid-zinc 

 process, and the glass tube, having been 

 heated to redness, the arsenical solution in 

 concentrated form is mixed with sulphuric 

 acid, and the mixture is slowly passed into a 

 separating funnel ; then more and stronger 

 acid is added, and the heat is kept up till the 

 decomposition is wholly effected. The arsenic 

 being collected in the form of a mirror of 

 metal, the tube is cut, at a safe distance from 

 the mirror, and weighed. The arsenic is re- 

 moved by heating, and the tube is weighed 

 again, when the difference gives the amount of 

 metallic arsenic. The method is capable of 

 detecting as little as the one thousandth of a 

 milligramme of the metal. In organic matters 

 the experimenters have detected a millionth of 

 a gramme in urine and in an extract from beef. 

 The experiments are claimed to show that the 

 presence of organic matter in considerable 

 quantity does not interfere with the recovery 

 of the entire amount of arsenic. 



VEGETABLE ANALYSIS. Professor Henry B. 

 Parsons, of Washington, D. C., has described 

 a method for the more accurate analysis of 

 plants. His apparatus includes a worm of 

 block-tin pipe, suitably connected with a glass 

 percolator, within wnich is suspended a smaller 

 tube, having a bottom of filtering-paper and 

 fine, washed linen. The weighed sample of the 

 finely-powdered herb is placed within this tube 

 for extraction. The solvent is introduced in a 

 glass flask, tightly fitted to the outer percolator, 

 and is volatilized by the application of heat 

 through a water-bath. A tared filter, pre- 

 pared by allowing fine asbestus, held in water, 

 to settle on the perforated bottom of a plati- 

 num crucible, is also provided and connected 

 with the receiving-vessel, while this in turn is 

 connected with a Bunsen's pump. The air-dried 

 specimen of the plant to be analyzed should be 

 ground or beaten till all the particles will pass 

 through a sieve having from forty to sixty 

 meshes to the linear inch. A part of this 

 should be further pulverized till it will pass 

 through a sieve having from eighty to one 

 hundred meshes to the linear inch. The finer 

 part of the sample is employed in the immediate 

 analysis, while the coarser part is reserved for 

 the separation of those proximate principles 



