§ 1] MODIFICATION OF VITAL ACTIONS 21 



0.01 % is fatal to bacteria. 



0.05% kills worms, molluscs, and isopods in 2 hours. (Loew, '88, 



p. 40.) 

 1.00% kills Spirogyra very quickly. (Cohn, '94, p. 6.) 



A weak solution seems to act ansesthetically upon Noctiluca. 

 (Massart, '93, p. 65.) 



When various radicals are substituted in H — CH : O, the 

 substance acts more like a catalytic poison. Thus, ethyl- 

 aldehyde (CHg — CHO) is anaesthetic ; and paraldehyde 

 (CH3-CHO)3 kills algffi in a solution of 0.002% in 24 

 hours and causes protoplasm to become immobile either (leuco- 

 cytes) after momentary stimulation (Demook, '94, p. 218) or 

 (Noctiluca) at once (Massart, '93, p. 66). 



Several derivatives of ethylaldehyde are poisonous. LoEW 

 ('93, p. 60) has shown that in a 0.1% solution of the neutral 

 sulphate of NH^ — CHg — CH : (OC2H5)2, amidoacetal. Infu- 

 soria, and diatoms die within 15 hours, and, somewhat later, 

 filamentous algae. 



Nitrous acid, as is well known, produces, even in great dilu- 

 tion, OH-compounds from amido-compounds (R — NHg) ; or 

 else, under certain conditions, especially with aromatic amido- 

 compounds, diazo-compounds result ; e.g. -^ 



C2H5 . NH2 + HO . NO = C2H5 . OH -h ISTs -I- H2O, 



amioe. alcohol. 



and 



CgHs . NH2 . HNO3 + HO . NO = CsHs . NsONOs -|- 2 H^O. 



anilioe nitrate. diazobenzene nitrate. 



Thus a solution of 0.001% of free nitrous acid is poisonous 

 to algiB, and more so than nitric acid. The lower fungi are 

 also very sensitive to nitrous acid. Its action as an acid is 

 weak, so that its salts are set free in the presence of even the 

 weaker organic acids. On this account, even neutral nitrates 

 kill such plants (some algse, e.g. Spirogyra) as have an acid 

 cell-sap. 



8. Sodic Fluoride. — The poisonous action of the fluorides 

 of the light metals, and especially sodium, has not hitherto 

 been explained. A 0.2% solution of NaF kills various algae 

 (Oscillaria, Cladophora, CEdogonium, diatoms) within 24 hours, 



