Ans. The vessel should be of glass, glazed earthenware, or lead.
Ques. At what density is the resistance of dilute sulfuric acid at a minimum?
Ans. At 1.260.
The percentage of concentrated sulphuric acid and of water per 100 parts of the electrolyte for various specific gravities is given by the following table:
| Sulphuric acid (Per cent.). | Water (Per cent.). | Specific gravity of Mixture. |
|---|---|---|
| 50 | 50 | 1.398 |
| 47 | 53 | 1.370 |
| 44 | 56 | 1.342 |
| 41 | 59 | 1.315 |
| 38 | 62 | 1.289 |
| 35 | 65 | 1.264 |
| 32 | 68 | 1.239 |
| 29 | 71 | 1.215 |
| 26 | 74 | 1.190 |
| 23 | 77 | 1.167 |
| 20 | 80 | 1.144 |
| 17 | 83 | 1.121 |
| 14 | 86 | 1.098 |
| 10 | 90 | 1.068 |
The electrolyte of the desired specific gravity may be purchased ready for use, but in cases where it is desirable to save freight, the acid may be diluted at the point of installation.
Ques. What is the effect of a deep containing vessel?
Ans. Parts of the plate surface may do more than their share of the work due to the difference in the density of the electrolyte at the top and bottom. The containing vessel should, therefore, never be deeper than about 20 inches unless some artificial means of acid circulation be used.
Ques. What is the effect of changes in temperature on the electrolyte?
Ans. The resistance of the electrolyte is changed, being less for increase of temperature.