20 CHEMICAL AGENTS AND PROTOPLASM [1'n. I 



or by acting on the aldehydes, 



E\ Ex 



)c = o + H,S = ;c = s + H.,O. 



H/ H/ 



It acts rather energetically upon algse and Infusoria. In Ver- 

 tebrates, the central nervous system is attacked and the oxy- 

 haemoglobin of the blood is altered. 



Sulphurous oxide (SO 2 ) attacks members of the aldehyde 



group, 



Ev E\ /SO,K 



OH 

 H/ H/ \ H 



aldehyde. 



0.1% kills lower fungi in a few minutes, 0.01% in a few hours. 

 Selenous oxide (SeO 2 ), which acts chemically much like SO 2 

 and has a much greater molecular weight (64 : 111), acts less 

 energetically as a poison. A 0.1% solution kills Spirogyra 

 and Zygnema in 3 hours, while 0.01% is scarcely injurious. 

 Tellurous oxide (TeO 2 , mol. wt. = 157) is non-poisonous, 

 although chemically closely allied to the two preceding. 



(BOKORNY, '93.) 



Aldehydes. - - The poisonous action of these substances de- 

 rived from oxidation of alcohol is dependent upon their insta- 

 bility. So we find that an aldehyde, which, like grape sugar, 

 is fairly stable, is likewise non-poisonous ; while formaldehyde, 

 which is very unstable and active, is correspondingly poisonous. 

 Aldehydes attack especially the unstable amides, affording ni- 

 trogenous compounds ; e.g. 



C 6 H 5 NH 2 + CH 2 = C 6 H 5 NCH 2 + H 2 O. 



Now, even in passive albumens, part of the N is in the form 

 of amido-groups ; for, in treating with nitric acid, much nitro- 

 gen is set free, which would not occur were all of the N second- 

 arily or tertiarily bound up. (LoE\v, '93, p. 58.) Hence the 

 poisonousness of aldehydes for living albumens. 



Formaldehyde. - -This substance (H -- CH : O) acts upon 

 propeptones and upon albumen, affording compounds which are 

 not readily soluble. An aqueous solution of 



