STORAGE OF NITRIC ACID

271

the so-called acid-resisting cements are disintegrated fairly
rapidly by nitric acid containing 50-60 per cent. HN03.

The problem has been met in America by the construction
of tanks of acid-proof bricks laid with acid-proof cement. The
most successful cement in this connection seems to be a
" Duro " cement having a sodium silicate basis, and at the
nitrate plant in Alabama tanks were successfully built having
a capacity for 500 tons of weak nitric acid.

Somewhat smaller tanks on similar lines have been built
in this country using acid-proof brick and a special sodium
silicate cement.1 These were made to hold 15-20 tons of
dilute nitric acid, and a con-
siderable amount of experience
has been gained in the construc-
tion of such tanks, which can
now be built successfully. Their
use has not as yet been exten-
sively developed in this country,
but for large-scale operations
they are undoubtedly a tremen-
dous improvement on the old type
of earthenware storage tank of
small capacity. .

It should also be mentioned
that the use of cast-iron and
steel tanks lined with tiles laid
in acid-proof cement has also

been extensively developed in recent years for nitric acid work,
particularly in Germany, not so much from the point of view
of storage as for reaction vessels, the contraction on setting, w
which is excessive with most acid-proof cements, being taken
up by slow compression of the tiles during setting.

Transport of Nitric Acid. The regulations of British
railways for the transport of nitric acid contain the following
conditions :—

1. The acid shall be packed in sealed stoneware jars pro-
tected by wickerwork. •

2. Bottles must be packed in cases or boxes, and the inter-

Fio. 126.—" Bosh " for Stor-
age of Weak Nitric Acid.

1 Brit. Pat. 119,966, 1917.