[A nalysis of] Rum anian industrial alcohol.
A. Zaha riaand D. Motzoc (Bui. Soc. Chim. Romania, 1926, 8, 57—91).—A critical discussion of the methods which have been proposed for the analysis and purification of alcohol leads to the following procedure. Esters are removed and determined by saponification (Girard- Cuniasse m e t h o d o f . “ Manuel pratique de l’Analyse
des Alcools,” 1899). The following improved G irard- Cuniasse method is the only one which removes acet- aldehyde completely from alcohol. The alcohol is- boiled under a reflux condenser with 4 g. of m-phenylene- diamine hydrochloride and 4 g. of aniline hydrogen phosphate per 100 g. of alcohol. The m ixture is then distilled under reduced pressure (15 cm.). Aldehyde is determined by colorimetric methods using Schiff’s re a g e n t; a solution of this reagent containing 1 • 5% of fuchsin is twice as sensitive as one containing 0-15% , and is quite stable. The total acidity is determined by direct titration with sodium hydroxide using phenol- phthalein as indicator. Furfuraldehyde is determined by Jorissen’s method (Ber., 1880,13, 2433) and higher alcohols by Komarovsky’s method (B., 1903,1259). The am ount of impurities in Rumanian industrial ethyl alcohols is, up to a concentration of 91°, independent of the concentration of the alcohol, but, except in the case of esters, depends on the raw material used. Thus, alcohol extracted from molasses has a high acidity and aldehyde c o n te n t; furfuraldehyde and higher alcohols occur in relatively large quantities in alcohol manufactured from cereals, but not from potatoes. The amount of impuri
ties varies in parallel with the amount of higher alcohols.
Most of the absolute alcohols examined contained furfur
aldehyde and especially esters and acids. The impurities are independent of the nature of the raw material. Recti
fied alcohol derived from potatoes is the purest, and th a t from a mixture of maize and molasses the least pure.
Industrial rectified alcohol is superior to th a t prepared in agricultural establishments. S. K. Tw eed y.
A n alysis of isopropyl alcohol. W. H. Simmons
(Perf. Ess. Oil Rec., 1927, 18, 168—169).—From an examination of various methods for the determination of acetone, the hydroxylamine method (cf. B e n n e tt; B., 1922, 391 a) gives the most satisfactory results in the presence of isopropyl alcohol. The method of Bennett and G arratt (B., 1925, 264) for the determination of ethyl alcohol and Durrans’ method (B., 1924, 731) for the detection of water are recommended. E. H. Sh a r p l e s.
Standardisation and stab ilisation of aconite preparations. III. E. E. Swanson and C. C. Har greaves(J. Amer. Pharm. Assoc., 1927,16, 296—301).—
Aconite tinctures and fluid extracts deteriorate rapidly within one year, and this loss in activity can be partially or totally prevented by the addition of sufficient acetic or hydrochloric acid to raise the value to 2-5—3-0.
For the standardisation of aconite preparations the bio
chemical method, in which the toxic dose for guinea-pigs or white mice is measured, is more reliable than the chemical method based on the ether-soluble alkaloid content (cf. Swanson and Walters, ibid., 1923, 12, 957 ; Swanson, ibid., 1924, 13, 1108). The guinea-pig and white mice methods agree well with standard aconite preparations, but not with deteriorated samples.
W. J. Po w e l l. A lkaloidal content of B ritish C olum bian-grow n H y d r a s t i s ca n a d en s is and A t r o p a belladon na.
R. H. Cla r k and (Miss) A. G. Win t e r (Trans. Roy.
Soc., Canada, 1926, [iii], 20, II I, 307—312).—The air-dry roots of Hydrastis canadensis grown in the Botanical Gardens of the University of British Columbia contained
B r itis h C h em ica l A b s tr a c ts —B.
Cl. X X .— Or g a n i c Pr o d u c t s ; Mé d i c i n a l Su b s t a n c e s ; Es s e n t i a l Oi l s. 5 0 5
1-5% of hydrastine and 1-7% of berberine. Atropa belladonna grown in the same place contained in the leaves 0-60% and in the roots 0-67% of total alkaloids.
R . Cu t h il l. Pharm aceutical incom p atibility of cam phor.
D. Mig lia c c i and A. Calo (Annali C'him. Appl., 1927, 17, 209—213).—The system camphor-ethylurethane shows a eutectic a t 28-1°, corresponding with 49% of
•camphor. Above this tem perature the mixtures are only pasty or liquid, whilst below it crystalline mixtures are
formed. T. H. Po p e.
Isom érisation of hydrocarbons by phenols. S.
Kondakov (Parfumerie moderne, 1926, 19, 212—223 ; from Chem. Zentr., 1927, I, 193—194).—The conversion of pinene (mixture of a- and (3-pinenes from turpentine of various origins) into camphene by heating with picric acid, 2 : 4 : 5-trinitro-m-cresol, trinitrothym ol, 2 : 4-
■dinitrophenol, 2 : 6-dinitio-p-cresol, dinitro-o-cresol, p- nitrophenol, 4-nitro-m-cresol, tribromophenol, methyl salicylate, resorcinol, o-cresol, phenol, etc., is investi
gated. When pinene (100 pts.) is heated with picric
•acid (20 pts.) a brisk reaction occurs a t 145° (water being given off), and continues for some time without further application of heat. Bornyl picrate, m.p.
■about 130—138°, contaminated with a little diterpene, is precipitated, and a colourless oil is obtained on steam distillation. Not more than 10% of monocyclic terpenes {dipentene and terpinene) and 3% of diterpene are formed- Below 140° there is no isomérisation to camphene, p a rt of the pinene remaining unchanged and the nopinene being converted into orthopinene. Bornyl picrate is hydrolysed by atmospheric moisture or by aqueous o r alcoholic alkalis, and by treatm ent with organic bases (e.g., pyridine) gives camphene. The first three fractions (b.p. 157—167°) from the steam distillate have a rather higher b.p. and lower rotatory power than the original pinene, give by oxidation with alkaline perman
ganate Wagner’s camphenecamphoric acid, m.p. 135—
136°, and no nopinic acid, and contain up to 75% of
■camphene. The fourth fraction (b.p. 167—170°) con
tains 50% of camphene and 50% of dipentene ; the fifth (b.p. 170—178°) is almost pure dipentene, and the last contains nitrogenous compounds having a musk odour and some borneol. When pinene is shaken with mercuric acetate solution in the dark there is formed a pasty, pale yellow complex compound which becomes black in the light. Mixtures of pinene and camphene react with mercuric acetate more slowly, and the presence of 75% of camphene prevents reaction. Sobrerol and unchanged camphene result from the action of mercuric acetate on the hydrocarbon mixture obtained by a single treatm ent of pinene with picric acid. A second picric acid treatm ent gives almost exclusively low-boiling hydrocarbons, and very little dipentene, diterpene, or bornyl picrate. Picric acid reacts less vigorously with the nopinene fraction (b.p. 160—163°) of French and American turpentines ; the products resemble generally those of the orthopinene fractions of the same oils, but differ in optical properties. Other tri- and di-nitrophenols give results similar to those with picric acid, but salts corresponding with bornyl picrate are not obtained with dinitrophenols. Mononitrophenols give a smaller yield of camphene, no bornyl ether, no steam bubbles, no
monocyclic terpenes, and only traces of diterpenes.
2 : 4 : 5-Trinitro-»?i-tolyl bornyl ether is formed in greater quantity than the picrate, and is hydrolysed less rapidly;
it yields camphene when heated. From halogenated phenols and pinene the yield of camphene is not more than 20%, and is independent of temperature (120—240°), time of heating (1—50 hrs.), and pressure (up to 4 a tm .);
no monocyclic terpenes, only traces of diterpenes, and no appreciable quantities of ester are formed. Phenol ethers isomerise a t most 20—25% of pinene to camphene ; below 200° no diterpene is produced, and a t 240° under high pressure only traces of dipentene, terpinene, and diterpene. The increase in rotatory power indicates th a t the orthopinene content has increased, whilst the nopinene is probably isomerised to a mixture of camphene and Z-a-pinene. The varying optical activity of pinenes from different sources is to be attributed not only to the proportions of I- and d-a-pinenes or l-a. and -(3-pinenes, but also to the proportion of orthopinene. The isomerisa- tion of pinene to camphene by means of phenols and phenol derivatives probably occurs in nature, camphene and phenols being commonly found together.
C. Ho l l in s. Saccharin drying. E. Bela n i (Chem.-Ztg. 1927, 51, 261—262).—Describes the most recent improvements in rotary dryers for saccharin. L. M. Clark.
Pinene content of Indian turpentine. II. M.
Mulanyand E. R. Watson (J. Indian Chem. Soc., 1926, 3, 258—259).—The results of various tests for pinene in the fraction (8-6—25%) of b.p. 155—160° of Indian turpentine oil, compared with those obtained with samples from other sources, show th at, contrary to the statem ent of Simonsen (B., 1920, 581 a), the pinene content of this oil is very small. I t contains a small quantity of A3-carene, detected as the nitrosate.
J. W. Baker. Function and form ation of essence of m in t by the secretive h airs of the plant. J. Rip e r t (Chim. et Ind., 1927, 17, 203—208).—From investigations on the formation of essence of m int during the growth of the plant (Mentha piperita) under various conditions, it is concluded th a t the essence is a product of de-assimilation, its formation being dependent on the balance existing between the forces of decay and growth. A. J. Hall.
E ssen tial oil content of so m e B ritish Columbian- grow n m in ts. R. H . Clark (Trans. Roy. Soc. Canada, 1926, [iii], 2 0 , III, 469—473).—Various species of mint have been grown in the Botanical Gardens of the Uni
versity of British Columbia. Mentha piperita and M.
viridis yielded a percentage of oil which was approxi
mately normal, b u t the yield per acre was very poor, largely due to a rust. M . pulegium, Tanacetuni vulgaris, and Monarda fistulosa, mollis, grew well and gave good yields of oil. Thymus vulgaris grew well, but gave a rather low yield of oil. R- Cu t h il l.
E ssen tia l oils from Greece. J. Gasopoulos (Arch.
Pharm ., 1927, 2 6 5 , 41—44).—The following data are for oils from cultivated plants. From Rosa damascena, 1922 and 1923 crops: dfs 0-8724, dft 0-8667; aD
— 2°, — 3°; nw 1-4660, n30 1-4640; setting-point, 16°, 19° ; acid value, 1-4, 1- 0; saponif. value, 16-5, 16-2 ; saponif. value, after acetylation, 255-9, 243-6 ; alcohol,
B r itis h C h em ica l A b s tr a c ts —B .
6 0 6 Cl. X X . — Or g a n i c Pr o d u c t s ; Me d i c h t a l Su b s t a n c e s ; Es s e n t i a l Oi l s.
Ci0H iSO, 87-4%, 81-9% ; ester, C]0H17-CO2Me, 5-7%>
5-67% . From Laurus nobilis, L. (three samples):
dis 0-9200, 0-9179, 0-9198; a D— 17-2°, — 16-8°,
— 18-2°; nD 1-4669, 1-4600, 1-4670; acid value, 1-5, 1-4, 1- 4; saponif. value, 34-5, 31-4, 29-4; ester value, 33, 30, 28. From Lavandula vera (three samples) :
¿0-889,0-881,0-884 ; a D — 7°, — 4°, — 8°; «D 1-4621, 1-460, 1-461 ; ester value, 86, 83, 100 ; linalyl acetate, 30%, 29%, 35% (these values are low because distillation was conducted by direct heating). From Rosmarinus ojficinalis (three samples): d 0-991, 0-908, 0-912;
<xD + 1 -5 1 °,+ 1-00°, + 1-40°; acid value, 0-3, 0- 5, 0- 3;
ester value, 3, 6, 4 ; bornyl acetate, 1-05%, 2-10%, 1 ■ 4% ; ester value after acetylation, 24, 20,18 ; saponif.
value, 3-3, 6-5, 4-3 ; borneol, 6-8% , 5-6% , 5-0% . W . A. Sil v e s t e r. E ssen tial o il content of C h a m a e c y p a r is n o o tk a - te n s is . R. H. Clark and C. C. Lucas (Trans. Roy.
Soc. Canada, 1926, [iii], 2 0 , III, 423—428).—The leaves of Chamaecyparis nootkatensis when distilled in steam yield 0-7—2-0% of their air-dry weight of a dextro
rotatory oil with d-° 0-855—0-8880, b.p. 155—280°, ftp 1-472 — 1-474, and saponif. value 10—30. Limonene, a-pinene,^-cymene, and probably (3-pinene and sabinene are present in the oil. R. Cu t h il l.
P hytopharm acological stu d y of d ig ita lis a ssa y . D. I. Macht and J. C. Krantz, j u n. (J. Amer. Pharrn.
Assoc., 1927, 16, 210—218).—Methods of biological assay of digitalis preparations employing animals are unsatisfactory owing to variations in the susceptibility of individual animals etc. I t is now proposed to employ seedlings of Lupinus albus, the inhibition of growth of the roots in a nutrient solution for plants (Shive solution) having been found to be proportional to the concentra
tion of the digitalis solution. The phytotoxic curve obtained has been calibrated in terms of “ cat units ” by careful comparison with the cat method, and a method for the examination of digitalis tinctures is described, an allowance being made for the toxic effect of the alcohol present in such tinctures by introducing equiva
lent amounts of alcohol into the control experiments.
C. O. Ha r v ey. D eterm ination of cineole in essen tial o ils. I.
Cajuput a n d eucalyptus o ils. Re p. Es se n t ia l Oil Su b-Comm. to t h e St a n d in g Comm, on Un i f o r m ity o f Analy tica l Me th o d s (Analyst, 1927, 5 2 , 276—279).—The British Pharmacopoeia method is regarded as unsatisfactory, and the o-cresol f.p. method is recommended. 3 g. of the oil and 2-1 g. of melted o-cresol are weighed successively into a test tube to an accuracy of one small drop (about 0-02 g.), a therm o
m eter graduated in fifths of a degree is inserted, the m ixture stirred, and the highest reading taken. The tube is then warmed and inserted into a wide-mouthed bottle through a cork and allowed to cool slowly until the previous reading is reached or crystallisation begins, when stirring and rubbing is begun and continued until there is no further rise of tem perature, the highest point reached being taken as the f.p. The test should be repeated until two concordant results are obtained.
If less than 50% of cineole is present pure cineole or a high-content oil may be added, or, if the mixed liquid s
do not crystallise in the first attem pt, 5 -1 g. of the pure recrystallised additive product, o-cresol-cineole, may then be added. A table of mean f.p. values for per
centages of cineole from 45-6 to 100 is given.
D. G. Hew ep..
Valuation of valerian root and valerian extract.
G. J. Ostling (Dansk. Tidsskr. Farm., 1927,1., 363—
374).—The nature of the active therapeutic principle in valerian root is uncertain, the quality of the material being usually judged on the appearance and odour of the drug and of the extract prepared from it. By boiling the drug with a mixture of alcohol and water (2 :1) for -J- hr., filtering, evaporating, and determining the weight of the dry residue, results were obtained which agreed with those obtained from extracts made in the usual way by percolation. The method of K atz is described in which 25 c.c. of the extract are evaporated to dryness with 1 c.c. of 33% sodium hydroxide solution.
The dry residue is dissolved in 100 c.c. of water, 20 c.c.
of 25% phosphoric acid are added, and the mixture is distilled. 110 c.c. of distillate are collected and titrated with 0 ■ liV-alkali, using phenolphthalein as indicator, the acid found being reckoned as valeric acid. Various specimens of the drug from different countries all give approximately equal acid values when thus examined, despite the fact th a t Japanese valerian contains 6% of ethereal oil as against 1% for the European drug.
Injection experiments on frogs were carried out, using alcoholic valerian extracts, each extract prior to employ
ment being evaporated to ensure removal of the alcohol, in order to eliminate errors due to the physiological action of this substance. The results showed th a t extracts prepared according to the method of the Finnish Pharmacopoeia using alcohol (2 pts.) and water (1 pt.) were more effective physiologically than those prepared by percolation with a mixture of water (3 pts.) and alcohol (1 pt.). Valerian extracts should be prepared by the former method, despite the fact th a t an extract of this type becomes turbid on the addition of water, whilst those prepared with weaker alcohol remain clear.
F urther experiments showed th a t extracts prepared from dried valerian root were apparently quite as effective physiologically as those made from fresh-cut valerian, although the results were not absolutely conclusive.
H . F. Harw ood. C rism er te st for essen tial o ils. A. An g e l e t t i
(Annali Chim. Appl., 1927, 17, 263—268).—The critical tem perature of solution in alcohol, suggested by Crismer (B., 1896, 300; 1897, 70; 1904, 451) as a distinctive physical constant, is applied to essential oils. The results are given for mixtures of each of a number of the oils with equal volumes of alcohol (d 0 • 8882 or 0 • 8899 a t 15°) (cf. Asboth ; B., 1897, 640) and for mixtures in various proportions with alcohol of d 0-8882 ; the critical solution tem perature rises with the percentage of the essential oil in the mixture. The test furnishes useful indications of the degree of purity of the oils.
T. H . Po p e. D ehydration of alcohol. Pe t r l ik.—See II.
Alcohol from cellulose etc. Mu t t iand Mo n t a lti.
—See V.
B r itis h C h e m ic a l A b s t r a c t s —B .
Cl. X X I.— Pk o t o o k a f u i c Ma t e r i a l s a n d Pe o o e s s e s. 5 0 7
Pa ten ts.
Preparation of arom atic carboxylic esters of alkoxy- and dialkoxy-aryldialkylam inopropyl alco
h ols. C. M annich (G.P. 437,925,23.4.24).—The alcohols are treated with benzoyl or nitrobenzoyl chloride, giving basic esters which have powerful local anaesthetic action and low toxicity. (3-Dimethylamino-(3-3 : i-methyl- enedioxyphenylisopropyl alcohol, m.p. 67—68°, prepared from Mosafrolebromohydrin and dimethylamine, when heated with benzoyl chloride for 1 hr. at 125°, yields the 0 -benzoate, m.p. 81—82° (hydrochloride, m.p. 206—
208°). The 0 -p-?litrobenzoale (hydrochloride, m.p. 216°), similarly obtained, is reduced by tin and hydrochloric acid to the p -aminobenzoate, m.p. 68°. fi-Dielhylamino-$- 3 : i-methylenedioxyphenyl\sopropyl alcohol, b.p. 170—
175°/14 mm., gives an 0 -benzoate '(hydrochloride, m.p.
205—207°), and an O-p -nilrobenzoate (hydrochloride, m.p. 220°). From $-piperidino-[3-3 : i-methylenedioxy- phenyUsopropyl alcohol, m.p. 77°, an O-benzoate (hydro
chloride, m.p. 204°), an O-p-nitrobenzoale (hydrochloride, m.p. 208°), and an O-p-aminobenzoate, m.p. 70°, are obtained. fi-Dimetkylamino-fi-anisylisop-opyl alcohol, b.p. 162°/17 mm., from anetholebromohydrin, gives an 0-j)-?iitrobenzoale (hydrochloride, m.p. 205°) and an O-p-aminobenzoate, m.p. 159°. The Q-\)-nitrobemoatc (hydrochloride, m.p. 198°) of fi-dimethylamino-fi-3: 4- dimethoxyphenyl\s,opropyl alcohol (from woeugenolbromo- hydrin) is described. C. Hollin s.
Iodising pyridine derivatives. S. G. S. Dick er. FromDEUTSCHE Go ld- & Sil b e r-Sc h e id e a n s t a l t,vorm. Ro e s s l e r (E.P. 246,501, 22.1.26).—Pyridine derivatives containing an amino- or hydroxy-group in position 2 or 4 are treated with iodine in the presence of a mild alkali (potassium carbonate, borax, etc.), caustic alkalis being avoided. The preparation of iodo-2-aminopyridine, 3-iodo-b-nilro-2-hydroxypyridine, m.p. 203°, and 5-iodo-2- hydroxypyridine, m.p. 275°, is described. The compounds have therapeutic value. C. Hollin s.
Production of 5-iodo-2-am inopyridine. C. Rath
(E.P. 246,842, 26.1.26. Cf. E.P. 251,578; 13., 1926, 608).—The method of Magidson and Menschikov (A., 1925, i, 301) is improved by the use of 10—30% alkali in place of the 3% alkali used in purifying the product of iodination of 2-aminopyridine with iodine in sodium or potassium iodide solution, and the pure 5-iodo-2- aminopyridine is crystallised from water instead of being extracted w ith ether. C. Ho llin s.
M anufacture of a sy m m e tric a lly acylated am ino-derivatives of arylarseno-com pounds.
G. New b e r y, and May & Ba k e r, Lt d. (E.P. 269,647, 19.1.26).—The reaction Ar ■ As 2 ■ Ar-j-Ar' ■ As 2 • Ar 2Ar-As2-Ar', where Ar is a diacyldiaminoaryl and Ar' a diaminoaryl group, either or both of which may contain other substituents, occurs when the two substances are dissolved in a common solvent and a precipitant for the product is added. By adding ether or excess of methyl- alcoholic hydrogen chloride to a mixture of 3 : 3 ' - diamino-5 : 5'-diacetamido-4 : 4'-dihydroxyarsenobenzene (prepared by reduction of nitrated 3-acetamido-4-hydr- oxybenzenearsinic acid with hyposulphite) and 3 : 3'- diamino-4 : 4'-dihydroxyarsenobenzene dissolved in methyl alcohol with the aid of a little methyl-alcoholic
hydrogen chloride, there is precipitated the dihydrochloride of 3 : 3'-diamino-5-acetamido-4 : 4'-dihydroxyarseno- benzene. 3-Amino-3'-acetamido-4: 4'-dihydroxyarseno- benzene is prepared by adding acetic acid to a solution of 3 : 3'-diamino-4 : 4'-dihydroxyarsenobenzene and its diacetyl derivative in dilute sodium hydroxide, and 3- am ino-3': 5-diacetamido-4 : 4'-dihydroxyarsenobenzene is similarly obtained from 3 : 3'-diamino-5 : 5'-diacet- amido-4 : 4'-dihydroxyarsenobenzene and 3 : 3'-diacet- amido-4 : 4'-dihydroxyarsenobenzene. The reduction of 3-nitro-5-acetamido-4-hydroxybenzenearsinic acid with sodium hyposulphite and magnesium chloride to the diaminodiacetamidodihydroxyarsenobenzene is de
scribed. From 3 : 3' : 5 : 5'-tetra-acetamido-4 : 4'-dihydr- oxyarsenobenzene, prepared by reduction of 3 : 5-diacet- amido-4-hydroxybenzenearsinic acid, and 3 : 3'-diamino- 4 : 4'-dihydroxyarsenobenzene there is obtained 3-amino- 3 ': 5'-diacetamido-4 : 4'-dihydroxyarsenobenzene.
C. Ho l l in s. M anufacture of asym m etrical arylarseno- com pounds. G. Ne w b e r y, F. J. Paxon, and May &
Ba k e r, Lt d. (E.P. 270,091, 7.5.26).—The processes of E.P. 11,709 and 11,901 of 1911 (B., 1912, 256), namely reduction of mixtures of two different arylarsinic acids etc., or condensation of arylarsines with a differently constituted arylarsenious oxide or dichloride, are applied to the manufacture of unsymmetrical arsenobenzcnes containing in one of the nuclei a glycinamide group.
Sodium phenylglycinamide-4-arsinate, N H 2-CO-CH2- NH-CgH j-As0(0Na)2, is reduced to the arylarsenious oxide, which is converted into the dichloride hydrochloride and allowed to react in aqueous solution with 3-amiuo-4- hydroxyphenylarsine hydrochloride to give 2>-amino-A- hydroxyarsenobenzene-i'-glycinamide. The same product results when a mixture of phenylglycinamide-4-arsinic acid and 3-amino-4-hydroxybenzenearsinic acid is reduced with sodium hyposulphite and magnesium chloride. S-Acetamido-i-hydroxyarsenobenzene-i’-glycin- amide, 3-amino-b-acetamidoA-hydroxyarsenobenzene-M- glycinamide, and 5-acetamido-2-hydroxyarsenobenzene-4:'- glycinamide aTe similarly obtained by reduction of appropriate mixtures of arylarsinic acids. The products have therapeutic value, and in the form of monosodium salts are suitable for injection. C. Ho l l in s.
Preparation of artificial m edicinal waters [from coal]. H. W. A. Branco(E.P. 269,660,4.5.25. Cf. G.P.
432,472 ; B ., 1927, 265).—The ashes from lignites, coal, or peat are extracted with water ; if desired the extracts may be further treated by the addition of salts (such as carbonates) or gases (such as carbon dioxide) or both.
R. A. A. Taylor. M anufacture of carbam ide from cyanam ide.
J. Br esla u er and C. Goudet, Assrs. to Soc. d’Etudes
Chim. p o u r l’In d. (U.S.P. 1,630,050, 24.5.27. Appl., 27.1.23. Conv., 4.2.22).—See E.P. 192,703; B ., 1923, 1152a.
XXI.— PHOTOGRAPHIC MATERIALS AND PROCESSES.
O xid isin g agen ts in the stu d y of the sensitivity of photographic em ulsions. W. Clark (Brit. J.
Phot., 1927, 74, 227—228, 243—245).—Preliminary
B ritish C hem ical A b s tra c ts— B .
608 Cl. X X I.— P h o t o g r a p h i c M a t e r i a l s a n d P r o c e s s e s .
experiments are described, based on the following con
siderations : it is assumed th a t the sensitive nuclei in the grains consist of silver sulphide, and the latent image of silver sulphide plus silver. If, then, an oxidiser can be found which will attack silver and not silver sulphide, it should not appreciably desensitise an ordinary unexposed plate, but should desensitise a pre-exposed plate. On the other hand, with an oxidiser which will attack both silver and silver sulphide, desensitisation should occur both with and without preliminary exposure of the plate, but perhaps more readily in the case of pre-exposure since silver would be more readily attacked
siderations : it is assumed th a t the sensitive nuclei in the grains consist of silver sulphide, and the latent image of silver sulphide plus silver. If, then, an oxidiser can be found which will attack silver and not silver sulphide, it should not appreciably desensitise an ordinary unexposed plate, but should desensitise a pre-exposed plate. On the other hand, with an oxidiser which will attack both silver and silver sulphide, desensitisation should occur both with and without preliminary exposure of the plate, but perhaps more readily in the case of pre-exposure since silver would be more readily attacked