List of therms» Nitric acid

Nitric acid (C.P., APPROX. 69 PER CENT) is one of Ihe most important chemicals in the lithography workshop. It is manufactured mostly by the Ostwald process, which oxidizes ammonia through a series of conversions from nitric oxide to nitrogen dioxide, and then to nitric acid. The concentrated chemical is a colorless liquid, commercialy available in several grades. The grade listed as "C.P." is preferable for lithography, although "A.R." grades are also satisfactory.

Nitric acid by itself or in solutions of water, gum arabic, or other chemicals. It chemically prepares stones by stabilizing or altering their printing images. Mixtures of the acid and gum are called etches, and, when applied and dried on the lithograph stone, they desensitize its surface to resist additions or encroachment of grease. Concentrated mixtures of the acid in either gum arabic or water attack the stone most energetically and set free carbonic gas in violent effervescence. These strong mixtures physically attack the surface of the stone and its grease content as well and thus can alter the image quality and its tonal values by eroding the grain of the printing surface.

Nitric acid is a highly corrosive chemical which must be kept in glass- or plastic-capped bottles. It should always be handled with great caution. It should be stored along with the other acids in a specially designed acid cabinet whose wooden construction and open shelving will withstand the corrosive action of acid fumes.

For daily use the acid is funneled with a glass funnel into a 100 ml, glass-stoppered laboratory drop bottle. When this acid is being mixed with water, the water must always be poured first; the acid is added afterwards. Because of the lower specific gravity ot water, a violent splashback would occur if the acid were poured first and the water added. Painful burns can result from such a splashback. Care should be taken to prevent contact of acid solutions with the skin and clothing and to avoid excessive inhalation of the vapors. In the event of contact, the area involved should be quickly and thoroughly flushed with water. Minor skin burns can be treated by an application of household baking soda (which should always be on hand in the acid cabinet). Serious injuries should always be attended to by a physician.