Extremely Dilute Acid and Alkali Solutions. 5 
through the side of which the condenser was brought out. Con- 
tamination from the fumes of the burner was thus completely 
avoided. In distilling, the first litre of water was thrown away, 
and the next two or three litres were collected. . 
Remarkably good water was obtained in this manner, the 
conductivity in one case being as low as 0°36 x 10~® reciprocal ohm, 
and generally being below 0°7x10-* This is probably due in 
part to the situation of the laboratory far from any large town, so 
that the air would contain relatively little carbonic acid and 
ammonia. Also the neck of the distillimg flask was very long, so 
that spray would not reach the condenser to any great extent and 
the ascending column of steam would be well washed. (Compare 
the washing of the steam as it occurs in Bourdillon’s apparatus.) 
Solutions of H,SO, and KOH of about milli-normal strength 
were prepared. Successive known quantities of these-stock solu- 
tions were added to specimens of distilled water (contained in 
a litre Jena glass flask) by means of a burette, and the resulting 
concentrations calculated. The conductivities were measured after 
each addition by pouring samples of these solutions into the con- 
ductivity cell. From these measurements the conductivities of 
the solutions in reciprocal ohms were determined and were plotted 
against the corresponding concentrations expressed in gram- 
equivalents per litre. 
Before giving the results, mention may be made of some of the 
precautions adopted to avoid contamination of the solutions during 
the experiments. As the solutions were extremely dilute, the 
possibility of contamination is naturally the first problem to be 
considered. The regularity of the results obtaimed in any one 
series, and the agreement between those of different series, were 
taken as evidence that these precautions were, on the whole, 
adequate. 
_ Contamination may arise from the solution of impurities, 
either from the air or from the glass surfaces with which the 
liquid is in contact. The experiments were carried out in a well- 
ventilated room. Whenever liquid had to be transferred from one 
vessel to another, the transference was made as quickly as possible. 
The openings to the conductivity cells were closed by small glass 
caps which effectively prevented fouling from the atmosphere. 
The flasks (of Jena glass) were of the ordinary long-necked 
measuring flask pattern, and were fitted with long glass caps to 
keep the stoppers and lips free from dust. Before use, they were 
rinsed thoroughly with warm potash and concentrated nitric acid; 
they were afterwards steamed for several hours; finally they were 
filled with distilled water and allowed to stand for several days. 
After this treatment they were inverted in distilled water with 
the stoppers loose, so that the lips and stoppers should be 
