CHEMISTRY. 



precipitation of the tannin in the state of an in- 

 soluble tannate. and the separation of the tan- 

 nin. The insoluble tannate of zinc is formed in 

 the lixiviated liquid by acting with ammonia on 

 zinc sulphate. This is then decomposed with 

 dilute sulphuric acid, and tannin is set free. The 

 zinc sulphide is separated from the liquid by 

 adding barium sulphide, when the insoluble zinc 

 sulphide and barium sulphate are formed. In 

 this manner are obtained directly extracts con- 

 taining from 20 to 30 per cent, of tannin free 

 from extractive matter and almost colorless. 



Three chlorobromides of silicon are described 

 by M. Besson, all being derived from silicon tet- 

 rachloride, SiCl 4 . The first two, SiCUBr and 

 SiClBrj, had already l>een prepared by M. 

 Friedel, by the action of bromine upon silicon 

 chloroform at 100 J C. in sealed tubes. M. Bes- 

 son obtains all three compounds, including the 

 hitherto unisolated SiClBr,, by the action of hy- 

 drobromic-acid gas upon silicon tetrachloride. 

 The first-named compound is comparatively easy 

 to separate by fractional distillation, and when 

 obtained in a fairly pure state serves for the 

 preparation of the second and third chlorobro- 

 mides by passing its vapor, instead of the tetra- 

 chloride, through the hot porcelain tube used in 

 the original process. The second-named prod- 

 uct boils, according to M. Besson, at from 102 to 

 105 C. It was found impossible to separate 

 the third compound from this second one by 

 fractional distillation, but taking advantage of 

 the fact that the second chlorobromide can not 

 be solidified at 60 C.. while the third com- 

 pound solidifies at 39 C.. and afterward dis- 

 tilling the solid obtained, the third compound, 

 SiClBr. has been isolated as a liquid boiling at 

 from 126" to 128 C. All three chlorobromides 

 combine directly with gaseous ammonia to form 

 additive compounds, white amorphous solid 

 bodies decomposed by water. 



In the determination of nitrates in water Al- 

 len Hazen and H. W. Clarke have found the 

 phenosul phonic-acid process of Grand Val and 

 Lajoux, with proper precautions, giving results 

 usually too low, and often much too low, so that, 

 while "it may be useful in some cases, they have 

 not been able to obtain results of the desired 

 accuracy. In the aluminum process, while the 

 action of the caustic soda and aluminum decom- 

 poses a portion of the organic matter with for- 

 mation of ammonia, this error is not found to ex- 

 ceed from 2 to 4 per cent, of the albuminoid 

 ammonia. With almost all ground waters, and 

 with most surface waters, it is insignificant. 

 It is only in the presence of large amounts of 

 decomposing organic matter that the result be- 

 comes uncertain. With potassium-nitrite solu- 

 tions in distilled water the results are satisfac- 

 tory, and are as accurate as the strength of am- 

 monia solutions can be determined at a single 

 trial by direct Nesslerization ; and the authors 

 believe" that their results upon waters, with the 

 exception noticed, are equally accurate. 



A method for the determination of barium in 

 the presence of calcium and magnesium, de- 

 scribed by F. W. Mar as rapid and accurate, de- 

 pends upon the fact that while barium chloride is 

 soluble to an extent not exceeding 1 part in 20,000 

 in pure concentrated hydrochloric acid, the soln- 

 lility increases very rapidly as the strength of 



the acid is diminished. In concentrated hydro- 

 chloric acid containing ether it is soluble to an 

 amount not exceeding 1 part in about 120,000. 

 In the separation of barium from calcium and 

 magnesium the chlorides of the earths are dis- 

 solved in the least possible amount of boiling 

 water and are precipitated with 25 c. c. of hydro- 

 chloric acid, with the addition of 5 c. c. of abso- 

 lute ether after ccoling. After standing a few 

 minutes the precipitate is filtered, washed with 

 hydrochloric acid containing about 10 per cent, 

 of ether, and dried at a temperature of from 

 150 to 200 C. 



Prof. Ramsay recommends as the best method 

 of preparing pure nitrogen peroxide the addi- 

 tion of the blue-green liquid, supposed to be a 

 mixture of this oxide with nitrous anhydride, 

 which is obtained by condensing the products of 

 the interaction of arsenious oxide and nitric 

 acid to a solution of nitric anhydride in nitric 

 acid and phosphoric acids, prepared by adding 

 phosphoric anhydride to well-cooled nitric acid. 

 After agitating the mixture the upper layer is 

 decanted and distilled. 



For lecture experiments showing the dissocia- 

 tion of soap by water, A. A. Breneman recom- 

 mends pouring an alcoholic solution of soap into 

 a glass cylinder half filled with distilled water, 

 which also contains phenolphthelein. The line 

 of contact of the liquid is colored bright red, 

 and on carefully stirring with a long rod a pink 

 flush is diffused through the mixed liquids. As 

 both are free from color before contact, the lib- 

 eration of alkali by the water is plainly shown, 

 and the theory of the action of soap is thus illus- 

 trated. 



Silicon bromoform, SiHBr, which had been 

 observed in an impure state by Buff and Wohler. 

 has been obtained pure by M. Besson by re- 

 peated fractional distillation of the product ob- 

 tained by passing a stream of dry hydrochloric- 

 acid gas over crystals of silicon heated to a tem- 

 perature just below redness. It is a colorless 

 liquid, which fumes vigorously at the first con- 

 tact with air and in a few minutes spontaneous- 

 ly inflames. The vapor forms highly explosive 

 mixtures with air. which occasionally detonate 

 with great violence. It remains liquid at tem- 

 peratures as low as 60 C. Water at once de- 

 composes it, and with solutions of alkalies the 

 decomposition is violent. 



Trisulphide of boron. BS, was first obtained 

 by Berzelius. and is also prepared by the modi- 

 fied processes of Deville and Wohler and of 

 Fremy. Of these, the process of Deville and 

 Wohler, by massing dry sulphureted hydrogen 

 gas over red-hot amorphous boron, is regarded as 

 best. The deposit of boron trisulphide appears 

 in the cooler parts of the tube, first opaline, then 

 in a porcelainlike form, and further along in 

 brilliant acicular crystals. These are violently 

 decomposed by water, yielding a clear solution 

 of boric acid, with evolution of sulphureted hy- 

 drogen. A snbsulphide of boron is described by 

 M. Sabbatier, which is left as a more volatile 

 black substance in the porcelain boat in which 

 the boron was placed in the first experiment. 

 and is also formed when the trisulphide of boron 

 is heated in a current of hydrogen. Two sele- 

 nides of boron. B,Sej and B 4 Se. corresponding 

 with the sulphides, are described by M. Sab- 



