THE ANALYST. 7 NOTES PROM OTHER JOURNALS. VOLUMETRIC ESTIMATION OF LEAD ACETATES. IN the courpe of a paper on ( I Volumetric Analysis,” read by Mi. Peter MacEwan at a meeting of the Edinburgh Chemists’ Assistants’ Assooiation, the tediousness of the pharmacopceial process for the above was referred to in the following words :- There is a special difficulty with lead acetates, due to the fact that they react with the oxalic acid to form insoIuble lead oxalate and acetic acid; consequently litmus and the other saturation indicators do not indicate the final reaction. The only indication is cessation of precipitation, but the oxalate subsides very slowly in the cold, and it is so bulky that one is apt to run in too much of the oxalic acid solution. By reversing the process and employing the heat of a water -bath to aggregate the precipitate, 1 find that the process can be conducted more expeditiously.The following are details : - PGz4niBi Acetm-The burette is filled with a 10-per-cent. aqueous solution of the E a l t (10 grammes in 100 o.c.), containing a little acetic acid to keep it clear ; 20 C.C. of oxalic acid solution, and about 2 02. of warm water are put into a flask, then 38 C.C. of the lead solution are run in and the flask placed on a water-bath. This quantity of lead solution contains 3-8 grammes of the salt, which is the amount allowed by the British Pharmacopaeia to combine with 20 C.C. of acid solution, if, therefore, the salt contain impurity, we shall require to pour more lead solution into the flask. It will be found that the heat of the water-bath causes the precipitate to subside more quickly than that of tho naked flame ; as soon as there is a fair amount of clear superstratum the flask is removed and a few drops of lead solution added ; if a precipitate form procccd cautiously, adding the solution, heating between each addition, until the last drop ceases to camo a precipitate.Note the number of 0.0. used and calculate the per- centitge of real acetate (B.P.) in the sample from the following formula (z=number o€ C.O. used) :- 38 x 100 X Liq. Phnrbi $tlbncetatis.-Twenty pammes of this solution should be made up to 100 C.C. with a little acetic acid and distiied water, the burette being filIed with the solution. Ten C.C. oxalic acid solution and two 02. of warm water are put into the flask, and about ten C.C.of the lead solution added ; then plaoe on the water-bath after a@;itating the contents thoroughly. After subsidence oontinue the addition of the lead solution, and proceed scc~~tdzt~tz nrtm until the find reaction is attained. Cabu 2nd ioia. 10 C.C. oxalic acid solution = 1‘37 gr. PbaO (C,H O& V = number of C.C. diluted lead solution used, &en 1’37 loo = p. c. of Pb20 (CAHsOp)a in mnple. - v Working by tho ordinary method, namely, by adding the acid to the lead solution, heating of the mixture does not appear to be advisable, because the precipitated normal lead oxalate reacts parliiaUy with the basic acetate to form basic lead oxalate, thus giving results which are slightly low. The following are percentages which I have obtahpd by both method8 .-8 THB ANALYST.A sample of liq. plumbi subacetatis estimated- I. By ordinary process. Ten grammes required 19 C.C. ox&& acid rjolution (mean of three titra- 11. By reversed method. Ten C.C. oxalic solution required 2S 0.0. of 20-per-cent. solution (mean of 111. By precipitation as chromate found 27.2 per cent. In I. and 11. the mixtures were filtered after titration ; both remained perfectly clear after cooling ; I. gave a very slight indication of lead with potassic chromate, and 11. less so. Another point worthy of observation is that in the ordinary method (using heat) the superstratum. is chaqcd with minute crystals, while in the reversed method it is perfectly clear until the final reaction is reached, after which (if more lead be added) it becomes similar to that of the ordinary method.This fact would seem to strengthen the supposition that basic oxalate is formed in presence of basic acetate.- Chemist af2d Dwggtst, Dccembes, 1883. tions) = 26.03 per cent. Pb,O (C,H,O,); three) = 27*4 per cent. Pb,O (C2H30& PREPARATION O F PURE CHLOROPHYLL. A, TSCHXRCH states that until now absolutely pure chlorophyll has nevcr yet been obtained. The assumption has always been that chlorophyll is a comparatively stable substance, whereas Tschirch finds it to be readily decomposed even by carbonic acid, with formation of chlorophyllane. He con- siders that only that substance which gives exactly the same absorption Bpectrum as is yielded by the living leaf can be oonsidered pwe cLlorophyll.He has obtained such a substance by the reduction of chlorophyllane by powdered zinc owr the water-bath. In alcoholic solution this substanoe has 8 beautiful emerald-green colour, and yields the following absorption spectrum :- Bmd. I. LI. 111. IV. End Absorption. Thin layer , . X = 68 to 63 62 to 59-5 55.3 to 55.7 54.0 to 52.5 50 Thicklayer .. X == GS.5 55.5 53.5 to 52.0 51 Two leaves , . X = 7 0 6 63 to GI 60.57 53 to 54 52 Three leaves . . X = 70-5 57 55 to 54 52 Absoyhm Spccclrum, of'.Living Zcnvcs. Band. I. II. III. IV. End Absorption. Pure chlorophyll thus prepared is a dark green liquid which has as yet resisted all attempts to crystallize it. It is easily soluble in alcohol, ether, and in fatty and essential oils, and very soluble in benzine ; it is difficultly soluble in melted paraffi, and insoluble in water.It is converted by dilute acidb into yellow chlorophyllane, and by concentrated hydrochloric acid into phyllocyanine. A solution of caustic potash decomposes it into a, fluorescent emerald-green substance, soluble in watery and resembling chlorophyll in its external appearance, and into a yellow substance soluble in ether.--BeircAtc dcr dceulschsqc c/mai.whcn #csoZZschft, November 23, 1853, translated for Ohemst and Dw,yg,st. A NEW METHOD OF OBTAINING PULP. G. ARCEDOLD macerates mood or straw, cut into suitable pieces, in dilute milk of lime : after twclvo hours introduces them into a suitable digester and saturates with sulphrous acid, the pressure amounting to four or five atmospheres. In two hours the material is so loosened up that, after washing with water and fusther treatment under pressure with three per cent. chloride of calcium and half a per cent.of aluminium sulphate dissolved in a little water, the stuff obtained without any further operation has the appearance of cotton, and can serve for the manufacture of fine qualities of paper,- h'c'Ciciztz& Amwicuii, Deoember lst, 1883. ESTINATION OF THE SULPHURIC ACID I N SULPHATE O F ALUMINA. THIS salt is taking the place of alum for many purposes : it is used considerably for paper making, and for this indu8try it is necessary that it should be free from acid, since the presence of a small pro- portion of free acid destroys ultramarine, and injures the sizing by causing transparent Hpots. Oscar Miller has reported the results of his experiments in the Bcrlaw Benchte, which show that methyl orange is the safest and best test for free acid. With pure sulphate of alumina it produces only an orange colour, but is very sensitive to free acid with which it produces a rose colour or pink, Ethyl orange is more sensitive, but tmms pink with some neutral sulphates. Tropsoline is not sensitive enough. By extracting the acid with alcohol the solution may be titrated, ming methyl orange an an indicator.-ij'&zti$c A wricnir, Docember 1 st, 1 S8 3.