CHEMISTRY. 201 



sulpliuiie acid (about 9-4 per cent strength) a pale-colored ring forms at 

 the juncture of the two liquids. The milk or food may be distilled and 

 the distillate, to which some casein dissolved in alkali has been added, 

 can be tested as above. This test is characteristic of formic aldehyde 

 and is not given by acetic aldehyde, but when much formic aldehyde is 

 present the blue color is not produced. 



An equally sensitive and more generally applicable test for formic 

 aldehyde is made by adding one drop of dilute aciueous solution of 

 phenol to the distillate from milk, mixing, and pouring upon concen- 

 trated sulphuric acid, when a bright crimson color appears at the point 

 of contact if formic aldehyde is present. L'henol and sulphuric acid 

 give an orange-yellow color with acetic aldehyde. — b. w. kilgore. 



Note on the estimation of formic aldehyde, H. M. Smith {Ana- 

 lyst, 21 {189<i), June, p. J 18). — The method is based on the oxidation 

 of formic aldehyde to formic acid in the cold by alkaline potassium 

 permanganate, and the decomposition of this into carbon dioxid and 

 water by boiling and further ndding permanganate. — u. w. kilgore. 



Note on Hehner's test for formic aldehyde, iST. Leonard (Ana- 

 lyst, 21 [189(1), June, p. 157). — The author found that Hehner's test 

 for formic aldehyde in milk (see above) was not easily obtained when 

 l)ure sulphuric acid was used, but that the commercial acid gave the 

 coloration distinctly and readily. The difference was traced to a small 

 amount of ferric chlorid in the commercial acid, which acted as a feeble 

 oxidizing agent, which is considered necessary to the success of the 



test. — B. W. KILGORE. 



Physical methods of butter examination, JST. Wender (Ztschr. 



Nahr. Untersuvh. und Hijij.Wnannl:, li> {189(i), pp. 46-49,85-87).— The 

 melting test. — Fifty grams of the butter to be examined is placed in a 

 warm, tall 100 cc. beaker and kept in a drying oven at 60° C. for 30 min- 

 utes. The author recommends the method for preliminary work. Pure 

 butter will, as a rule, give a perfectly clear oil, while mixtures of butter 

 and oleomargarine will be more or less turbid. 



The emulsion tests. — A review of the methods of Mayer, Jalir, Katz, 



etc. — F. W. WOLL. 



Photometric method for the quantitative estimation of sul- 

 phuric acid, J. I. D. UmBa {Chem. News, 73 {1896), No. 1908, p. 285).— 

 The author found that by adding solid boriuni chlorid to sulphuric 

 acid of known strength (very dilute) and observing the height of a 

 column in a cylinder similar to a ISTessler cylinder, through which an 

 ordinary candle flame was visible (holding the candle directly under 

 the cylinder and shading the cylinder from direct light), the product 

 of the height of this column by the percentage of sulphuric acid in the 

 solution was a constant. This constant for 11^804 was found to be 

 0.0r>l»0 and fcu' SO3, 0.0482. Hence the amount of sulphuric acid in 

 dilute solutions can be estimated by adding borium chlorid, observing 



