US2137234A - Basic lead styphnate and process of making it - Google Patents

Description

' ducing basic lead styphnate in these forms.

Patented Nov. 22, 1938 PATENT FF1E BASIC LEAD STYPHNATE AND PROCESS OF MAKING'IT vWilli Brun, Bridgeport, Conn, assignor to Remington 'ArmsCompany, Inc., acorporation of Delaware No Drawing. Application June 2, 1933, Serial No. 674,049. Renewed February 11, '1937 5 Claims.

This invention relatesto the manufacture of styphnic-acid and certain of its salts, and, contemplates improvements and refinements in the production ofv styphnic acid,.the practice of which results in a product adapted to. be. made into salts having certain desirable properties and characteristics. a ,-,More specifically-,the invention contemplates ,the controlofthe shape and form of, the crystals of certainsalts of styphnic acid, particularly basic lead styphnate, and certain methodsin the manufacture of styphnic 'acidwhich enable the acid to form salts having novel and desirable crystal shapes. 1 a V j The manufacture of basic lead styphnate and particularlyia red crystalline form thereof is described in this applicants prior co-pending application, Serial No. 569,835, filed October 19, 1931, Patent No. 1,942,274. It may be briefly summarized as follows:

A solution of styphnic acid and sodium hydroxide, in the proportions of 12.2 grams of styphnic acid and 8 grams of sodium hydroxide in 400 c. c. of water, is dropped into a lead nitrate solution of the concentration of about 35 grams of lead nitrate in 350 c. c. of water. The temperature is maintained between and C.,

and the styphnic acid-sodium hydroxide solution is at first dropped into the lead nitrate solution very slowly. The first precipitate is a previously known yellow amorphous or partly amorphous basic lead styphnate which, if the sodium hydroxide-styphnic acid solution is at first introduced quite slowly, changes over to a heavier red crystalline basic lead styphnate which quickly settles out.

When in the practice of the process above outlined ordinary styphnic acid is used, the crystals of basic lead styphnate are rather thick hexagonal plates. They are less fragile and sensitive to friction and shock than the previously known yellow needle crystals. The present invention comprises the discovery of other crystalline forms of basic lead styphnate, and methods for pro- The novel crystal shapes result from the use of styphnic acid made in accordance with certain procedures constituting a part of the present invention. The manufacture of ordinary styphnic acid will first be briefly described:

The raw material is resorcine (CeH4(OI-I)2). By treatment with concentrated sulphuric acid resorcine is sulphonated to resorcine-di-sulphonic acid, CsH2(OH)2(SO3H)2. The resorcine-di-sulphonic acid is then nitrated with concentrated amounts of certain foreign substances.

nitric acid. The precipitated styphnic acid is separated from the residue by centrifugal action or by filtration, and subsequently washed first with a dilute mineral acid andthen with water.

If the sulphonation of the resorcine is complete,

the resulting product is pure styphnic acid of a bright yellow color and low gravimetric density,

from which crystalline salts are formed only with great difiiculty.

The present invention comprises the discovery that the character of the styphnic acid may be altered in such a Way as to control the crystal shape of thesaltswhich it forms by the addition, during the operation of sulphonating, of small 7 Such variations in the styphnic acid and in the crystal shape of its salts, particularly the basic lead salt, are produced by the use of any one of a number of different substances. Moreover, each substance has the property of producing its own I characteristic effects and crystal shape, each of these shapes differing from the others. For example, if to a batch comprising 110 grams of resorcine and 460 c. c. of 98% sulphuric acid there be added 10 c. c. of concentrated nitric acid the resulting styphnic acid is darker in color and less voluminous and its salts have different physical properties. The further addition of .1 gram of tri-oxy-methylene results in a styphnic acid which yields its basic lead salt in crystals'of a shape differing very substantially from the usual crystals of this salt. Said crystals are somewhat elongated square or rectangular prisms, as distinguished from the usual hexagonal plates, and appear to be more sensitive to shock and friction than the hexagonal plates. Two opposite faces of the rectangular prismatic crystals appear to be substantially square, while the other faces are tiallyrectangular cross section. The addition of c. c. of water produces an acid whose salt forms in crystals which are nearly cubical and exceptionally firm and dense. The addition of a small amount of aluminum produces salt crystals which are nearly cubical and unusually clean.

The use of sulphuric acid instead of 98% results in a mixture of amorphous salt and comparatively short rectangular crystals. Acetic acid produces a. striking effect in that the salt crystals are large short rectangular prisms with rounded corners, somewhat resembling the crystals of normal lead styphnate.

It should be remembered that the foreign substance is introduced in the sulphonation operation in the preparation of styphnic acid, and that the described crystal shapes are those of the salts, particularly the basic lead salt of the acid produced in the presence of the foreign substance.

No satisfactory theoretical explanation of these effects can be offered. The foreign substances which cause them do not fall within any recognized class, or appear to have any property in common other than their ability to change the crystal shape of basic lead styphnate from hexagonal to tetragonal. Among themselves their effects differ in that each produces a crystal which is easily identified and distinguished from the crystals produced by the others. Tri-oxymethylene, cathechol, glucose and aluminum, all tend to form oxides, hence should have a reducing action. On the other hand, phenol and acetic acid are not such reducing agents. Diluting the sulphuric acid and adding water tend to limit'the amount of water that can be absorbed by the sulphuric acid, hence to lower the concentration of the nitrating nitric acid and increase its oxidizing effect. Thus the general effect (production of tetragonal crystals) cannot be definitely attributed either to oxidation or reduction, nor is it limited to either organic or inorganic com-' pounds.

What is claimed is:

1. In the manufacture of salts of styphnic acid by the sulphonation and nitration of resorcine to styphnic acid and the subsequent formation of a crystalline salt therefrom, the method of controlling the shape of said salt crystals which comprises the addition during sulphonation of trioxy-methylene.

2. In the manufacture of salts of styphnic acid by the sulphonation and nitration of resorcine to styphnic acid and the subsequent formation of a crystalline salt therefrom, the method of controlling the shape of said salt crystals which comprises the addition during sulphonation of trioxy-methylene in the proportions of approximately .1 gram of tri-oxymethylene to grams of resorcine and 460 c. c. of concentrated sulphuric acid.

3. As a composition of matter, basic lead styphnate in the form of tetragonal prismatic crystals.

4. In the manufacture of basic lead styphnate by a process including the sulphonation and nitration of resorcine to styphnic acid and the subsequent formation of a crystalline salt therefrom, the method of forming said basic lead styphnate in tetragonal prismatic crystals which comprises the addition during sulphonation of tri-oxy-methylene.

5. In the manufacture of salts of styphnic acid by a process comprising the sulphonation and nitration of resorcine to styphnic acid and the subsequent formation of a crystalline salt therefrom, the method of controlling the shape of said salt crystals which comprises the addition of trioxy-methylene during the preparation of said styphnic acid.

35 WILLI BRUN.