4 CHEMICAL AGENTS AND PROTOPLASM [Cn. I 



acids act as intense poisons, apparently by directly yielding 

 oxygen atoms to the plasma proteins. 



Sodic chr ornate (Na 2 CrO 4 ). Many anaerobic Schizophytes 

 are killed even by a 0.05% solution of this salt. Splenic fever 

 bacteria do not develop in a 0.05% solution in bouillon; in 

 an agar-agar solution, they do not cease to develop until a con- 

 centration of 0.5% is reached, although they no longer produce 

 spores in a 0.05% solution. Sodic chromate also acts strongly 

 on algae. (LoEW, '93, p. 16.) 



Potassic dichromate (K 2 Cr 2 O 7 ). A 0.1% solution kills algae 

 (Spirogyra) in a few hours. 



Potassic permanganate (KMnO 4 ) is an energetic poison for 

 algae and Infusoria. A 0.2% solution kills Infusoria (Para- 

 mecium) in one minute. 



Chlorine, bromine, and iodine, as well as hypochlorous acid 

 salts, act, even in very considerable dilution, fatally upon 

 all organisms, by splitting water, forming hydro-halogen com- 

 pounds, and leaving the oxygen to unite with the living proto- 

 plasm. The action of bromine upon glucose may be written 



C 6 H 12 6 + Br 2 + H 2 = C 6 H 12 7 + 2 HBr. 



glucose. 



(LoEW, '93, p. 15.) 



BINZ has pointed out that (on Infusoria) the poisonous 

 action of these three halogens, like their other chemical prop- 

 erties, diminishes with increase of atomic weight, in the series 

 Cl, Br, I. (Compare the osmotic effects of the halogens, p. 72.) 



Potassic chlorate (KC1O 3 ) also similar salts of I and Br 

 oxidizes in an essentially different fashion from the permanga- 

 nates. For the latter oxidize even dead organic matter, but 

 the former does not. This reagent may be considered a pas- 

 sively oxidizing one. Concerning its visible effects, we find 

 that bacteria in general are injured by a 2% solution; with 

 weaker solutions in nutrient media the bacteria reduce it to 

 KC1. The anaerobic forms are affected by a 0.5% solution; 

 the aerobic withstand up to 3%. Algae (Spirogyra) die after 

 a few days in a 0.01% solution of the salt. (LoEW, '93, p. 17.) 



Arsenious acid (H 3 AsO 3 ) and to a less degree arsenic acid 

 (H 3 AsO 4 ) are poisons which BIKZ and SCHULZ ('79) believe 



