October 5, 1882. ] JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 817 
interesting account of the lacquer industry of Japan. From this it 
appears that vast plantations of the Lacquer Tree (Stagmaria verni- 
ciflua) are grown for the express purpose of extracting their sap, 
which is usually done when the trees have attained the age of ten 
years. One province alone sends out no fewer than 1500 workmen, 
whose business it is to tap the trees and collect the sap which exudes 
from them ; and when it is borne in mind that this process is going 
on all over the mainland, it will at once be seen that the industry is 
very extensive. Each tree yields sufficient juice to fill a 3-oz. bottle, 
and each workman during a season of about four months is expected 
to bleed about one thousand trees, the total yield of sap amounting 
to between 120,000 and 140,000 gallons. For his services during the 
season a first-rate workman is paid the munificent sum of £13, though 
inferior men get considerably less. The wholesale trade is entirely 
in the hands of two or three large merchants, who dispose of the raw 
material to the manufacturers. These prepare it in a manner which 
they keep secret, and contrive to sell it in its manufactured state at 
the same price which they paid for it, from which the Consul not 
unnaturally concludes that it has to undergo considerable adultera¬ 
tion before it finally reaches the hands of those who use it in artistic 
work. 
WHAT IS THE MANURIAL VALUE OF PHOSPHATE 
OF MAGNESIA? 
In my last letter on this subject, page 290, I brought forward 
certain facts which appeared to me to show that the question of 
the valuation of different forms of phosphoric acid was in a very 
unsatisfactory condition ; and I concluded that letter by pointing 
out ihat, if so slight a degree of solubility as Dr. Voelcker found 
to be possessed by phosphate of lime in guano was sufficient for 
all the wants of plants, and if the solubility of precipitated phos¬ 
phate of lime was so materially increased, as he found it to be, by 
dilute solutions of ammomacal salts, we are able better to under¬ 
stand why Jamieson obtained, with finely ground mineral phos¬ 
phates, the results which have astonished the agricultural world. 
Ground coprolites are by no means insoluble in distilled water, 
and must be appreciably more so in solutions of ammoniacal salts 
or of carbonic acid. I cannot here forbear quoting the opening 
paragraph from your able review of the Report of the proceedings 
of the Sussex Association for the Improvement of Agriculture 
(i Journal of Horticulture, page 110). “Dogmatism in things 
scientific is not worth indulging in, for what is accepted as fact 
to-day is to-morrow showm to be fallacious. A year or two ago 
phosphates in manures were reckoned as of little or no value, and 
only acid-treated phosphates were considered of use for plants. 
The Aberdeenshire experiments, conducted by an able and original 
chemist, Mr. Thomas Jamieson, dealt the first blow to the old 
theory—for it never was more than a theory, though universally 
accepted as proved fact, and acted on as such.” Four years since 
a little work on artificial manures was published by Mr. Alfred 
Sibson, who was formerly an assistant in Dr. Voelcker’s private 
laboratory, and was subsequently the Assistant Professor of 
Chemistry in the Royal Agricultural College, Cirencester. At 
page 91, second edition of the work, he writes: “Nevertheless, 
as manufacturers do not appear disposed to press their rights 
on this point [the identification and estimation of precipi¬ 
tated phosphate] some modification of the foregoing scale (' in 
which precipitated phosphaie is reckoned at seven-eighths of the 
value of soluble phosphate’) is necessary to render it generally 
useful and applicable in those cases in which the precipitated 
phosphate is not shown, either from the refusal on the part of the 
analyst to recognise it, or from a simpler and less complete 
analysis only being desired.” Now if the results obtained by 
Voelcker by acting on precipitated phosphate with distilled water 
in comparison with those obtained by acting on guano, which Dr. 
Voelcker considers to be “sufficiently soluble for the wants of 
plants,” are to be relied on we shall not be disposed to quarrel 
with Sibson’s valuation. From guano one gallon of distilled water 
dissolved 2 52 grains only of phosphate of lime ; of precipitated 
phosphate, whilst the precipitate was still moist, 5'56 grains per 
gallon ; and wffien the precipitate was burnt and finely ground, 
2 20 grains. In practice, precipitated phosphate of commerce, 
though far more soluble than it would be after burning, would 
not be as soluble, undoubtedly, as wffien freshly precipitated ; but 
we might safely assume that it would be considerably more soluble 
than phosphate of lime in guano. 
At page 90 “Artificial Manures” Sibson says that precipitated 
phosphates are now determined by more chemists than formerly, 
especially on the continent, yet there is and has been great hos¬ 
tility shown towards its recognition in some quarters for reasons 
which need not be entered upon here. “At the same time, I 
should plainly state,” he adds, “ that I consider it [precipitated 
phosphate] distinct from soluble phosphate ; ” and no doubt it is 
so, for the soluble phosphate in acid superphosphates is undeniably 
injurious in soils deficient in lime to neutralise the acid, and in 
clay soils there is greater chance of loss of phosphoric acid from 
excessive rains ; whilst, on the other hand (see review of the 
Report on the Sussex proceedings, page 110 Journal of Horticul¬ 
ture), one of the ascertained benefits resulting from the use of 
dissolved phosphate over undissolved is that it gives the plants 
the advantage of a quicker start where only chemical manures are 
used ; ” but “ although this is the case, it is shown in the report 
before us that dissolved phosphate has a tendency to fail towards 
the end of the season, whilst the undissolved holds on, and in the 
end gives equal and in some instances superior results." 
The results obtained by Jamieson in Scotland led to a contro¬ 
versy between Voelcker and himself, in which, whilst Jamieson 
argued that crude pbosphatic materials finely pulverised were 
very nearly as valuable as superphosphates for the growth of 
Swedish Turnips, Voelcker, “ viewing the matter from a different 
standpoint,” after quoting numerous experiments made by himself 
and others, enunciates his opinions in the following eight propo¬ 
sitions, which I extract from the Journal of the Chemical Society, 
No. ccxxiv., page 640, vols. xxxix. and xl. Amongst these propo¬ 
sitions I beg that the reader will particularly take notice of the 
first, as it alludes to a remarkable fact, the knowledge of which is 
essential to the comprehension of the rationale of plant food. It 
appears, strange as it may seem, that the soluble phosphate of our 
manures (as well as their ammonia, potash, &c.), again becomes 
insoluble, generally speaking, before being taken up by the plant; 
and that their activity is dependant upon their thorough diffusion 
through the soil in this physically fixed condition, as Liebig 
termed it. 
1, Phosphates are not readily taken up by plants in a soluble 
form, but must be returned to an insoluble condition before they 
yield their useful properties. 
2, The efficacy of calcium phosphate corresponds with the 
minuteness of division in which it is found in a manure. 
3, The finer the particles in a phosphatic material the easier it 
is dissolved in water, and the more energetic its action in a 
manure. Coarsely ground coprolites and other minerals are less 
useful than the same materials in fine powder. 
4, Calcium phosphate in porous soft bones is more soluble and 
energetic than in hard bones, and is more available in bone meal 
than in crushed bones. 
5, Calcium phosphate in crystallised mineral phosphates—Nor¬ 
wegian, Canadian, and Spanish apatites, for example—is less 
soluble and energetic than the same amount contained in porous 
phosphatic materials, such as certain descriptions of phospho- 
guano. 
6, Treatment with acids renders the material completely soluble 
in water, and the so-formed superphosphate when put into the 
ground is precipitated in a very fine state of division. 
7, In this precipitated state the insoluble phosphate is im¬ 
measurably more finely divided than it could be obtained by 
mechanical means, and is consequently more energetic than any 
raw material mechanically ground. 
8, The author’s conclusion is that the chemical treatment with 
acid is the cheapest and best way of rendering mineral phosphates 
useful for agricultural purposes. 
With these propositions I believe few authorities on the subject 
will be found to disagree, excepting perhaps with the last. I 
would, with deference, suggest for Dr. Voelcker’s consideration 
whether to them might not be added with advantage a ninth 
proposition to the following effect :—“ If, after a phosphate has 
been dissolved by treatment with an acid, the phosphoric acid is 
precipitated in combination with a base by which the acidity 
produced may be neutralised, whilst the precipitated salt possesses 
a sufficient degree of solubility to eusure thorough distribution 
through the soil, perfect conditions are attained for rendering the 
phosphoric acid useful in plant nutrition.” 
“Precipitated phosphate,” says Sibson in “Artificial Manures,” 
page 123, “ is therefore as valuable as soluble phosphate, except 
in so far that it has lost the power of spontaneous diffusion 
possessed by the latter; and this lessens its commercial value, 
since it is this condition of solubility which it is wished to secure, 
and for which we chiefly pay in buying superphosphates.” It is 
my contention, I may here state, that in precipitated phosphate 
of magnesia we have a substance “reduced to a degree of minute¬ 
ness infinitely surpassing anything obtainable by grinding,” ac¬ 
companied by a degree of solubility such as all agricultural 
chemists, when they will take the trouble to think about it, must 
admit to be sufficient for the attainment of perfect diffusion.— 
Inquires. 
Flowers in Autumn. —Some of our plants are still attractive. 
We are gathering at this time Viola odorata and The Czar Violet 
jC 
