90 Report of Schimmel § Co. 1922. 



Chemical Preparations and Drugs. 



Benzaldehyde. — In our last Bericht 1 ) we accurately described our method of 

 quantitative determination of chlorine in benzaldehyde. The apparatus then shown in 

 the picture, and supplied by the Leipzig firm of F. Hugershoff, has meanwhile been 

 slightly modified. 



Both the U-tubes serving as absorbing vessels have been provided with a short 

 pipe each which can be closed by means of a piece of rubber tubing and a pinch- 

 cock, so that the absorbing liquid can now be more easily removed. Furthermore, 

 the glass tube connection the two U-tubes has been provided with a small bulb, as 

 sometimes the liquid of the first U-tube passed over into the second. 



In addition we would mention the fact that the air in the laboratories is liable to 

 contain hydrochloric acid gas and that then even passing it through dilute silver 

 nitrate solution may not free it entirely from chlorine. We therefore connect the 

 apparatus with the fresh air outside by means of a glass tube passed through a small 

 opening in a window. 



As previously mentioned 1 ) we consider the indication of "benzaldehyde, technically 

 tree from chlorine" as a nuisance, liable to cause confusion to the detriment of the 

 honest dealer. Our opinion has since been confirmed, for its is almost incredible 

 what stuff is frequently offered under above designation. There are products of all 

 shades, from a slight to the most pronounced chlorine reaction, and it is only a 

 matter of how elastic the conscience of the supplier may be for terming the product 

 "technically" or, as it is now called, "commercially free from chlorine". 



Out of the many samples which have been examined in our analytical laboratories 

 we would only mention one, just to show what amount of cheek some 'suppliers have. 

 The constants were as follows: di 50 1.0633, « D + 0°6', n D20 o 1.54054, completely in- 

 soluble even in 10 volumes of 50 percent, alcohol, acid v. 12.5 = 2.7 percent, benzoic 

 acid, chlorine reaction: extraordinarily strong. This shows that the article was absolutely 

 unsatisfactory, not a single one of the constants coming up to the requirements for 

 benzaldehyde. It is even too bad for a crude product, as results from the defective 

 solubility and the excessive specific gravity, which latter cannot be explained by an 

 excess of benzoic acid, into which benzaldehyde may be converted by oxidation. These 

 two properties referred to induced us to examine the sample a little more closely, as 

 far as the small quantity permitted. It resulted that the product contained only 68 per cent, 

 of benzaldehyde. The quantity at our disposal was not large enough for further in- 

 vestigation regarding the admixtures, §c. 



W. von Rechenberg 2 ) prefers Beilstein's copper oxide test for chlorine in benz- 

 aldehyde to the well-known combustion method. After comparative tests, he ascribes 

 more exact results to the former. 



We have stated on previous occasions 3 ) that, in our opinion, the combustion 

 method is decidedly more accurate and reliable than the copper oxide test, and we 



i) Berkht (German) 1921, 56. — 2 ) Chem.-Ztg. 45 (1921), 627. — 3 ) Report April 1912, 151. 



