April, 1922
THE JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
the best indication of its efficiency. If most of the particles of a lead arsenate containing a deflocculent settle immediately while there is just sufficient in suspension to obscure its real physical condition, such an arsenat#ewill not be as efficient m another with better physical properties and having
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no spreader. The practical efficiency of any deflocculent or spreader that may be added to a commercial lead arsenate can best be determined by comparison of results obtained in field practice where ordinary care only is exercised in the application of the spray.
Napht halenesulfonic Acids'" IV-Solubilities
of Some Amino Salts of Naphthalenesulfonic Acids By H,Wales3
COLORINVHSTIGATION LABORATORY, BUREAU OF CHEMISTRY, WASHINGTON. D . C.
In the following paper the solubilities of the salts a-and p-naphthylamine with some naphthalenesulfonic acids have been de(ermined between 25" and 98' C. and the results plotted. Allotropic changes are indicated for two of the salts and an interesting relation between the solubility and structure of a series of isomers is shown.
ample, a-naphthylamine naphthalene-a-sulfonate and anaphthylamine naphthalene-1,6-disulfonate showed much lower solubilities ~7hile the a-p, and a-1,5-compounds became almost twice as soluble. The nature of this change is not understood at this time. No change in this new compound could be brought about by recrystallization.
HE method of Ambler and Wherry4 for the separation and identification of the sulfonic acids of naphthalene depends upon the formation of insoluble salts with a- and pnaphthylaniine. With the exception of their solubilities, which were noted in only a general way, all properties of these salts have been thoroughly de~cribed.~Inasmuch as their complete separation depends upon the solubility, it wm thought advisable to determine this over a wide range of temperatures. .
T
h!hTEOD
An excess of the salt was placed in a thermostat with the solvent and stirred at constant temperature for one day. At the end of this period a weighed amount of solution was drawn off through a pipet having a cotton plug over the end, evaporated to dryness, and the residue weighed. No difficulty caused by crystallization in the pipet was experienced at high temperatures for the reason that all the salts used form highly supersaturated solutions. Pure water proved to be impossible for use as a solvent, because of tlhe rapid hydrolysis of the more soluble compounds. However, a 0.01 N solution of hydrochloric acid was sufficient to prevent hydrolysis except in the case *of a-naphthylamine naphthalene-l,6-disulfonate. No effect of acid of this strength on the solubility could be determined, and the solvent has the added advantage of more nearly giving the conditions under which the salts are prepared4 and used in detecting the sulfonic acids. I n the case of a-naphthylamine naphthalene-lI6-disu1fonate, the rapid hydrolysis of this salt made a slightly different method necessary. The solvent, heated to a temperature 15" to 20" higher than that desired, was placed in a Dewar bulb with more than enough salt for saturation a t this higher temperature. The liquid was then allowed to cool slowly with rapid stirring. When the desired temperature was reached, after 2 or 3 hrs., a portion was drawn off through a plugged pipet and treated as above. Freshly prepared samples were used in all these determinations since it was found that on standing for several months changes took place which seriously affected the solubility. For exNovember 28, 1921. Published as Contribution 56, from the Color Investigation Laboratory, U,S. Bureau of Chemistry, Washington, D. C. 8 Associate Chemist (Physical). 4 THIS JOURNAL, 12 (1920), 1085. 6 Ambler, I b i d . , 12 (1920), 1081, 1194. 1 Received
2
Considerable difficulty was experienced with solutions of a-naphthylamine naphthalene-2,7-disulfonate above 70" C. and with all solutions of a-1,6,since on partial evaporation on the steam bath these solutions would set to solid masfies from which the last traces of water could be removed only by prolonged heating.
RESULTS The results, calculated to grams of salt in 100 g. of solvent, are given in the accompanying table. When plotted, these results give the curves shown in the charts. An interesting relation between the structure of a series of isomers and their solubilities is apparent from these results. From the very meager information available on the solubilities of isomers it was noted that the para or most
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symmetrical isomer is the least soluble,6 and that the order of solubility of the ortho and meta compounds varies according to the solvent. I n general, the order is o-m-p for water and m-o-p for all other solvents except alcohol. For nlcohol both arrangements are found. In the case of these compounds which are salts of disulfonic acids, the order of solubility, starting with the most z5O
to the crystalline variety. The solubility measurements, however, gave no evidence of a transition point below 100" C. The curve for the ferrous salt of the naphthalene-psulfonate is also shown as this compound is the one iised to identify the p-acid. Although this salt crystallizes at ordinary temperatures with six molecules of water of crystallization, and no break was found on the solubility curve, it W
P-NAPHTHILAHI~E SILTS 1-815
1 MONO
(5 Fa a'A"rol
was thought advisable to express all values in terms of the anhydrous salt. SOLUBILITIGS O F SOME AMINO SALTS OF NAPHTHALENESULFONIC IN GRAMS PER 100 GRAMS OF SOLVENT (0.01 N HC1)
c.
2,f3 Amphi-
2,7 Pros-
show clearly that the ana- and amphi-acids are the most symmetrical. The influence of the base apparently determines which shall be the least soluble. The epi-compound, on the other hand, shows no symmetry and is found to give the most soluble salts with both a- and p-naphthylamine, The pros- compound, while showing the symmetry of neither the ana- nor amphi-isomers, has symmetry about the line of the two common carbon atoms and, as would be expected, is more soluble than either of the latter but less soluble than the epi-compound. The curve for a-naphthylamine naphthalene-p-sulfonate shows an allotropic change a t about 54" C. and that for a-naphthylamine naphthalene-a-sulfonate, one at about 66" C. These allotropic forms have not yet been isolated. The forms described by Ambler are probably represented by the lower parts of these curves. When a solution of pnaphthylamine naphthalene-a-sulfonate is saturated a t the boiling point and cooled rapidly without stirring, a stiff jelly is formed, which, if disturbed, will quickly change 8 The only exception found was that of the dinitrobenzenes with water a s a solvent.
i
i
4-6P
4.5
I
I
I
I
3aa
l,5 Ana-
I
SULFONAIiS SULFONAI i s
2 sa
soluble, is: epi- 1,6; pros-, 2,7; amphi-, 2,6; ana-, 1,5 for the a-naphthylamine salts; and epi-, 1,6; pros-, 2,7: ana-, 1,5; amphi-, 2,6 for the p-naphthylamine salts. The formulas
Vol. 14, No. 4
25 30 35 40 45 50 55 60 70 80 90 98
c. 25 30 35 40 45 50 55
60 70 80 90 98
c. 25 30 35 40 45 50 55 60 65 70 80 90 98
a-16 0,0605 0.0694 0.0883 0.0972 0.1033 0,1253 0.1563 0.1638 0.2212 0,2902 0,4010 0.4635 0-1,s 0.0727 0,0765 0,0887 0,1107 0,1233 0.1493 0 1701 0.1882 0 2562 0,3204 0.4427 0,5887 a-a
0,3125 0.4131 0.6007 0.5991 0.7340 0.8366 0.9733 1.113 1.305 1.368 1.571 2.028 2.651
a-Naphthylamine Salts a-1,6 a-2,6 2.29 3.20 4.21 7.15 9.59
...
...
... ...
ACIDS
a-2,7 0,8689 0.9805 1.162 1.364 1.599 1.931 2.405 9.386 10.3 35.2 87.7
...
8-Naphth ylamine Salts ' 8-2,6 8-1.6 8-2,7 0,1327 0.0296 0,1454 0.0386 0.1917 0.0412 0.2160 0.0422 0.2737 0.0594 0.3312 0,0614 0.4241 0.0702 0.4684 0.0806 0.6791 0,1093 0,1626 0,9735 1.433 0,2207 1.861 0,2943 Monosulfonafes @-a Fe-8 (anhyd.) a-8 8-8 0,1735 0.3022 0,0563 0.2039 0,2391 0,0599 0,2078 0.3470 0,2533 0.4233 0,0736 0.2985 0,3150 0.5135 0,0816 0.3875 0.3986 0.6174 0.1008 0.4420 0.4954 0.7711 0,1171 0.5398 0,6044 0.9171 0,1434 0.6246 0,7391 1.056 0,1656 0,6542
......
0.8493 1.283 2.132 2.951
......
0,2393 0,3395 0,4667 0.6218
.....
1.141 1.829 2.980 4.790
.....
1.393 1.985 2.882 3.764
