OXYGEN CONSUMPTION IN ACIDS. 30! 



The water used is thus the ground water of the Chicago region. 

 It is high in salt content, particularly in carbonates. This water 

 has been analyzed for us by the State Water Survey Division of 

 Illinois. It seems desirable to present the analysis at this point. 



3. Behavior of Planaria in Acid. When the water is acidified 

 no alteration in the behavior of the worms is noticeable until a 

 certain degree of acidification is reached. This degree is different 

 for different acids, but is generally in the neighborhood of 

 pH 5.5 to 5.0. The animals lose the ability to glide about, 

 owing apparently to a paralysis of the ciliary mechanism. They 

 exhibit continuous writhing movements, and secrete a large 

 amount of mucus. With greater acidification, they lose ability 

 to cling to the glass and fall to the bottom of the container, 

 where they remain, often with slight writhing movements. They 

 are, when this condition is attained, extremely elongated and 

 generally more or less curved, the ventral surface being concave, 

 the dorsal convex. In short, as in the case of the marine animals, 

 a sufficient degree of acidity induces a paralysis of the motor 

 mechanism, which appears to involve the cilia first, the muscles 

 later. 



4. Experiments with Hydrochloric Acid. A large number of 

 experiments, about seventy, were performed with this acid. The 

 normal respiration in normal water (pH 8.0) for one hour was 

 first determined. The water was then acidified to the desired 

 degree and the rate of oxygen consumption in the acid water 

 immediately tested. An interval of one hour in the acidified 

 water was then passed, another determination made in freshly 

 acidified water, another hour passed, and a third determination 

 carried out. It will thus be evident that the respiration during 

 the first, third, and fifth hours in the acid was tested. This was 

 the general procedure in the earlier part of the work. The 

 acidity ranged from pH 7.5 to 4.5 at 0.5 pH intervals. It seems 

 unnecessary to present in detail the mass of data thus accumu- 

 lated as all of the experiments gave the same general result. 

 A set of typical determinations of the action of hydrochloric acid 

 at different hydrogen ion concentrations is given in Table IV. 

 The averages of all of the experiments performed with this acid 

 are summarized in Table VI. The action is graphed in Fig. I. 



