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Updated: May 28, 2025
If we cut across a stalk of the garden rhubarb, we can see, with the aid of a microscope, the fine needle-shaped crystals of oxalate of potash lying among the fibres of the plant, a provision for an extra supply of the oxalic acid which is the source of the intense sourness of this vegetable.
"Then you have no prejudices as to which is the best developer, pyrogallic acid or ferrous oxalate, not to mention such recent decoctions as eikonogen, quinol, and others?" No, the boy had none. "Well, that's what I like. I like a young man whose mind is open to conviction." The boy was not a conversational success. He evidently did not enter into the spirit of the artist's remarks.
As a matter of fact, a piece of the lid, when subjected to heat, blackens, which proves the presence of an organic glue cementing the mineral matter. The solution becomes muddy if oxalate of ammonia be added and deposits a copious white precipitate. These signs indicate calcium carbonate. I look for urate of ammonia, that constantly-recurring product of the various stages of the metamorphoses.
!Method B! !Oxalate Standards! PROCEDURE. Weigh out two portions of pure sodium oxalate of 0.25-0.3 gram each into beakers of about 600 cc. capacity. Make a blank test with 20 cc. of manganous sulphate solution and a volume of distilled water equal to that of the titrated solution to determine the volume of the permanganate solution required to produce a very slight pink.
Antimony may be precipitated in its metallic state from a hydrochloric acid solution, but it does not adhere very firmly to the electrode. If potassium oxalate is added to a solution of the trichloride, the antimony may be readily reduced, but the metal adheres still less firmly to the electrode than it did in the first instance.
The Peruvian borax sometimes contains nitre. For testing the purity of refined borax the following simple tests will usually suffice. On passing sulphuretted hydrogen into the solution, no coloration or precipitate should be produced. Calcium Salts. The solution should not give a precipitate with ammonium oxalate solution. Carbonates.
Now while these proportions may be the best for the development of a negative, they are not, according to my experience, the best for gelatine bromide positive enlargements; I find, indeed, that potassic oxalate should not have more than one-eighth of the ferrous sulphate solution added to it, otherwise it will not hold in proper solution for any length of time the compound salt formed when the two are mixed.
The ammonium oxalate is added in excess to the solution, which is then heated, and four more grammes of the solid salt added. The separation of the nickel is as rapid as that of the cobalt. The nickel is precipitated as a gray, compact mass, tightly adhering to the electrode.
The binoxide of commerce, as taken from the mine, is well sampled, powdered, and dried at 100 deg.C. 0.5 gramme of this is taken and placed in a 250 c.c. flask; in analysis the binoxide on the filter, from the treatments noted under separation is thoroughly washed with warm water; it is then washed down in a flask, as above, after breaking the filter paper; sufficient water is added to one-third fill the flask, and about twice the approximate weight of the binoxide in the flask of oxalate of potassa; these are agitated together.
A drop or two of the prussiate solution then gives a brown colour, even if but traces of copper are present. Magnesia. Suppose lime and magnesia are present. You may first evaporate to a small bulk, adding a drop of hydrochloric acid if the liquid becomes muddy. Then add ammonia and ammonium oxalate, when lime alone is precipitated as the oxalate of lime.
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