f
mercury there are possibilities of leakage of air from the blower
connections and hence, to note this immediately, the blower system is
immersed in a tank filled with heavy lubricating oil. The connections
are so well made, however, that leakage rarely occurs, and, when it
does, a slight tightening of the stuffing-box on the shaft makes the
apparatus tight again.

ABSORBERS FOR WATER-VAPOR.

To absorb 25 to 40 grams of water-vapor in an hour from a current of air
moving at the rate of 75 liters per minute and leaving the air
essentially dry under these conditions has been met by the apparatus
herewith described. The earlier attempts to secure this result involved
the use of enameled-iron soup-stock pots, fitted with special
enameled-iron covers and closed with rubber gaskets. For the preliminary
experimenting and for a few experiments with man these proved
satisfactory, but in spite of their resistance to the action of
sulphuric acid, it was found that they were not as desirable as they
should be for continued experimenting from year to year. Recourse was
then had to a special form of chemical pottery, glazed, and a type that
usually gives excellent satisfaction in manufacturing concerns was used.

This special form of absorbers presented many difficulties in
construction, but the mechanical difficulties were overcome by the
potter's skill and a number of such vessels were furnished by the
Charles Graham Chemical Pottery Works. Here again these vessels served
our purpose for several months, but unfortunately the glaze used did not
suffice to cover them completely and there was a slight, though
persistent, leakage of sulphuric acid through the porous walls. To
overcome this difficulty the interior of the vessels was coated with hot
paraffin after a long-continued washing to remove the acid and after
they had been allowed to dry thoroughly. The paraffin-treated absorbers
continued to give satisfaction, but it was soon seen that for permanent
use something more satisfactory must be had. After innumerable trials
with glazed vessels of different kinds of pottery and glass,
arrangements were made with the Royal Berlin Porcelain Works to mold and
make these absorbers out of their highly resistant porcelain. The result
thus far leaves nothing to be desired as a vessel for this purpose. A
number of such absorbers were made and have been constantly used for a
year and are absolutely without criticism.

Fig. 28 shows the