CHEMISTRY. 121 



, The use of the Schloesing method for determining nitric nitrogen in 

 presence of organic matter, P. LieI'hti and E. Ritter [Ztschr. AiKih/t. C'he)n.,4£ 

 {790o), Xo. 4, pp. 205-232). — The authors report tests which refute Pfeiffer and 

 Thunuanii's objections to this method and show its rehabiUty. Certain modifica- 

 tions in detail are described. 



Action of potassium permanganate on indigo, with reference to the 

 determination of nitrates by the indigo-carmine method, W. i\. Jj.wci and 

 W. M. WiLKiE {Jour. Soc. Chem. Ind., 22 {190S), No. 11, pp. 67S, «7^).— The dis- 

 cordant resnits of a series of experiments witli dihite potassiun^ nitrate, si;l])luu-ic 

 acid, and indigo titrated with tenth-normal potassium permanganate lead to the 

 conclnsion that "if this method of estimating nitrates is to be of any accuracy, an 

 absolute similarit}' of conditions, both as regards time and temperature, must be 

 observed." 



Tintometric estimation of nitrites and nitrates in -water, F. W. Richardson 

 and P. Rollings {Jour. Soc. Chem. Ind., 22 {1903), No. 10, pp. 616, ei7).— Sutton's 

 phenol-disulphonic acid method using Lovibond's tintometer is recommended. 



The preparation of ammonia-free water for water analysis, J. B. Weems, 

 C. E. Gray, and E. C. Mvers ( Conirib. Ikp)t. Agr. Chem., Iov>a State Col. Agr. and Meclr 

 Arts, No. 6, pp. 112, lis). — The use of sodium peroxid in i)reparing ammonia-free 

 water is describeil. 



A new method for the titration of free and combined sulphuric acid, W. 

 ]\ItJLLER (^(T. Dent. Chem. GeselL, 35 {1902), No. 9, pp. 1587-1589; ahs. in Bui. Soc. 

 Chim. Paris, 3. ser., 30 {1903), No. 5, p. 478). — The method proposed dejiends upon 

 the fact that when a solution containing sulphuric acid is added to a hot solution of 

 benzidine hydrochlorate suli^huric acid is precipitated and may be removed by filtra- 

 tion. The amount of sulphuric acid may be calculated by titration of a measured 

 quantity of the benzidine reagent before and after precipitation by means of soda 

 solution and phenolphthalein. The reaction which occurs is shown in the following 

 e(juation: K,S0j-(V,Iis(NH.,),.2Il('l =2RC1 K'i,H,(NIL ),.ILS(),. 



A volumetric method of estimating free and combined sulphuric acid, 

 (i. Frerichs {Arch. Pharm., 241 {1903), No. 2, pp. 159, ifiO).— The method, wiiich is 

 Ijiiefly described, depends upon the fact that free and combined sulphuric acid give 

 a silver salt insoluble in alcohol. 



Note on the determination of solids in the analysis of vinegars, W. Frear 

 and C P. Bei.stle {Pnnisijlrama Sta. Ppjl. 7902, pp. 165-168). — Comparative tests 

 were made of drying to a constant weight in a water oven at al)out 100° C, and dry- 

 ing at ordinary room temperature over sulphuric acid. The solids determined bj' 

 drying in the water oven averaged 1.39 per cent and by drying over suli)huric acid 

 2.03 per cent, making a difference by the 2 methods equivalent to 0.64 per cent of 

 the entire vinegar. To determine the nature of this loss elementary analyses were 

 made of the residues, which showed an average percentage of carbon calculated to 

 the original weight of vinegar used of 0.48 by drying in the water oven and 0.72 by 

 drying over sulphuric acid, making a difference of 0.24 per cent. The difference was 

 greater than coulil be accounted for by the excess of the acetic acid in the residues 

 obtained by <lrying over sulphuric acid. As the residue from the water oven was 

 not a(;id the destruction of the fixed acids or their neutralization by bases set free 

 from other coml)inations was indicated. "These results demonstrate In'yond cavil 

 the fact that the usual method of determining vinegar solids by evaporation at 100° C'. 

 is attended by the elimination, either by volatilization or decomposition, of con- 

 stituents other than water, alcohol, and acetic acid, and that this loss of materfals 

 properly classed among the solids is entirely too great to be overlooked in any investi- 

 gation requiring an absolute determination of the quantity of such materials. They 

 further show that, while the ordinary method is still practicable where purely relative 



