Vol. VIII. No. 86'. 
IMPERIAL INSTITUTE JOURNAL. 
[February. 1902.] 43 
amount of tannin present was less than that found in more modern bookbinding leather ; 
and (4) in most cases the old leathers, which had stood so well, were tanned with either 
sumach or oak-bark. 
With [reference to the first two points it needed no investigation to prove the. superiority 
of the older over the modern practice. The splitting or paring down of the skins, often to such 
an extent that only the thin grain surface remains, cannot but diminish the durability, since it 
removes the toughest part of the leather, while the custom of drying many kinds of leather in 
a tightly-stretched condition is also inimical, as it destroys the elasticity and, by displacing 
the fibres, hastens the deterioration. The other two points, viz., the influence of different 
tanning agents and the extent to which the tanning was carried, were made the subjects of 
careful investigation, especially as in nearly every case in which a modern leather had stood 
well it was found to have been tanned with sumach. Sumach and oak-bark are still used for 
the preparation of the best classes of leather, but large numbers of skins are treated with other 
materials, such as quebracho, larch bark, gambier, and mimosa bark, while thousands of 
skins tanned with turwar bark are imported from India. The latter, which are known in the 
trade as Persian morocco, Persian sheep, and East Indian calf, are usually re-tanned with 
sumach in this country, and had been found to be the least durable of all modern bookbinding 
leathers. Comparative experiments were, therefore, made by tanning different skins, calf, goaf, 
and sheep, with the tanning materials in common use, and then testing the leathers by 
exposing them for long periods to the action of light, heat, the combustion products of coal 
gas, etc., in imitation of the usual library conditions. In every case the most resistant leather 
was that tanned with sumach, followed in order of merit by myrobalans, chestnut extract, 
oakwood extract, oak bark, gambier, larch bark, quebracho, pistacia and tamarix ; while the 
worst specimens were the East Indian skins tanned with turwar bark, especially those which 
had been re-tanned here with sumach. This latter practice was shown by a further series of 
experiments to diminish the life of the leather by about half, probably owing, as will be seen 
later, to the use of sulphuric acid in the process, but at the best these skins are almost 
worthless for bookbinding purposes. It was also found that in every case the leather which 
was lightly tanned was much more resistant than the corresponding piece which had been 
more heavily tanned in accordance with the present custom. 
Another important point which demanded attention was the decay of modern calf, 
tanned with oak bark, and for the purpose of investigation several of these skins were 
obtained from librarians and bookbinders. It was found on examination that most of these 
contained free sulphuric acid, which had evidently been used to brighten the colour, in 
quantities varying from 0*2 to o*8 per cent., and consequently a number of other skins 
perfectly free from acid were also obtained for comparison. Pieces of these leathers were 
subjected to the tests already mentioned, with the result that the specimens free from acid 
proved very satisfactory, whereas those which contained acid were very adversely affected, 
changing in colour to red-brown and becoming hard, brittle and easily abraded by friction. 
The practice of using sulphuric acid for brightening the colour of oak-tanned calf is quite 
recent and only became general twenty or thirty years ago. It has a wonderful effect in 
removing stains from the skins, in rendering the colour brighter and more uniform, so that 
the leather presents a much better appearance, but its use appears to be injurious. In these 
experiments it was again observed that the more heavily tanned skins were the least 
resistant. 
The methods employed in dyeing and finishing the leather were next examined, in order 
to determine whether any of these were likely to be the cause of deterioration. It was con- 
clusively proved that if acid had not been used in the dye-bath the leather was in no way 
affected by the exposure to the test conditions and, in fact, the finishing appeared to protect 
the surface ; but, on the other hand, in those cases where an acid dye-bath was employed the 
leather showed signs of decay, becoming hard and brittle. In these last experiments five 
different kinds of skin were employed, viz., calf, sheep, goat, seal and pig, and of these the 
two first were most affected by the acid. 
The examination of a large number of samples of different kinds of leather of English 
manufacture showed that the use of sulphuric acid, either for improving the colour or in the 
dyeing process, has become almost universal. Thus, Dr. Parker found that 36 out of 38 
samples of morocco, 12 out of iS samples of skivers, and 27 out of 32 samples of calf, 
contained free sulphuric acid, while this was also present in all the samples of Persian goat, 
Persian sheep and pig skin, numbering 18, 23 and 6 respectively, which were examined. 
The same condition was found in French and German bookbinding leathers ; eight different 
samples of French Levant morocco were all found to contain a large quantity of free sulphuric 
acid, varying from cr6 to 1*3 per cent., and of twelve samples of German origin, eleven 
contained acid, the maximum amount being 0*85 per cent. The large percentage of free 
acid remaining in the leather was rather surprising in view of the thorough rinsing to which 
the skins are finally subjected in the tanyard, but experiments showed that it is practically 
impossible to completely remove the acid by simply washing in running water. A piece of 
Persian leather, containing one per cent, of sulphuric acid, was continuously washed for five 
days, and was then found to retain slightly over 0*2 per cent. It is therefore recommended 
that in those cases where it is absolutely necessary to use sulphuric acid, the skins should be 
washed with water containing sodium (or potassium) lactate or acetate, whereby the free 
acid can be completely neutralised without producing any objectionable effects. 
The quality of the leather manufactured from skins imported in a preserved condition 
was also investigated. Many of these are preserved in salt and, on tanning, were found to 
yield a leather much weaker than the dried or fresh skins, especially in those cases where 
slight decomposition had occurred. Large numbers of sheep skins, pickled in a solution of 
salt and sulphuric acid, are exported from New Zealand and Australia, and the leather 
obtained from these was also very greatly inferior to that from unpickled skins. 
The practices of the bookbinder also received attention, with the result that the methods 
employed for the production of sprinkled leathers, and the use of oxalic acid for brightening 
the colour, arc condemned, as tending to the rapid deterioration of the leather. The various 
pastes employed were usually found to lie harmless, but much damage is done to the leather 
by stretching it loo tightly over the back of the book. 
One other fact of interest was brought out by the enquiry, viz., the large extent to which 
ordinary sheep skin is got up in imitation of other leathers. Books were met with 
apparently hound in Levant morocco, hard grain morocco, straight grain morocco, pig skin, 
calf skin, crocodile and alligator leathers, and all of these on microscopic examination were 
proved to be common sheep skin which had been stamped with the special grains and 
markings of the different skins. 
These results completely justify the findings of the Committee, and it is to be hoped 
that the attention which has been devoted to the question will result in a great improvement 
in the durability of the present bookbinding leathers. 
THE MANUFACTURE OF VARNISH. 
It is well known that oil varnishes are usually made by healing fossil resins, such as the 
“kauri” of New Zealand, until they melt, and stirring into the molten mass linseed oil 
heated to a temperature sufficiently high to ensure complete miscibility of the oil and resin. 
In such a process a great loss of volatile matter from the crude resin occurs, often to the 
extent of 40 or 50 per cent, by weight ; this loss is not only uneconomical, but is a source of 
danger, since the material driven off by the heat is very inflammable. It has frequently been 
suggested that the mixture of oil and resin might be more satisfactorily made by heating the 
materials together under pressure, and a series of experiments of the kind has been made by 
/* 7 
Mr.' A. J. Smith, the results of which have been published in a recent number of the Journal 
of the Society of Chemical Industry ( November 30, 1901). In these laboratory experiments, 
the resin, in a finely powdered and dried state, was mixed with oil and heated in a Jena 
glass tube at a pressure of about two atmospheres. Solution occurred in the case of kauri 
in about twenty minutes with the formation of a pale yellow varnish, which, owing to its 
large content of resin, required more turpentine than usual to thin it down to working 
condition. The author has successfully carried this process out in melters of ten gallon 
capacity, so that it appears to be workable under manufacturing conditions, but he gives no 
information regarding the qualities of the varnish so produced, and in particular of the 
permanence or otherwise of the material when applied to wood. 
It may be mentioned here, as a point of considerable importance, that the brilliance of a 
varnish depends upon the non-crystalline character of the resins from which it is made, and 
the dull appearance which many cheap varnishes acquire after a time is due to the crystallising 
out of simple resin acids like abietic and pimaric acids, which are the chief constituents of 
such resins as colophony, but also occur to a smaller extent in the more valuable resins 
kauri and anind. When the latter are treated in open vessels, the simpler resin acids 
already referred to volatilise, leaving the really valuable constituents behind, which, when 
combined with oil, produce a satisfactory varnish. It is to be expected, therefore, that the 
pressure process as suggested by Smith will not furnish a varnish of the same high quality, as 
regards permanence, as the older process of melting in open vessels. 
In the discussion which followed the reading of this paper, Dr. Lewkowitsch remarked 
upon the unsatisfactory state of chemical knowledge on the subject of resins, and the conse- 
quent difficulty of classifying them and ascertaining the purity of commercial specimens, in 
spite of the fact that the manufacture of varnish was carried out on a very large scale, and 
was a matter of great industrial importance to this country. There is no doubt that a 
thorough investigation of many of the natural resins Would disclose new sources of material 
for the manufacture of the finer kinds of varnish, and bring to light methods of treating the 
poorer resins, so as to improve their varnishing properties ; but the subject is such a difficult 
one that it is not likely to be taken up while so many more promising fields are open to 
chemical investigators. 
MINERAL PRODUCTION IN INDIA. 
There has recently been issued from the office of the Director-General of Statistics for 
India the annual report on the production of minerals in that country, which gives some 
interesting figures showing the extent to which the mineral wealth of India is at present 
exploited. 
It appears that the average output of salt per annum is nearly 1, 000,000 tons, derived 
from the salt mines of the Punjab, the lakes and wells in Rajputana and Upper Burma, and 
from sea water in Madras, Bombay, Sind, and Lower Burma. 
In spite of the wide-spread production of salt in the country, considerable quantities 
are imported from Europe vid Liverpool and Hamburg, the average import for the last five 
years having been 398,000 tons. 
The production of saltpetre (nitre) has declined considerably since the development of 
the Stassfurt mines has enabled Germany to manufacture potassium nitrate from the Stassfurt 
minerals and Chili saltpetre (sodium nitrate), but there is still produced in India a con- 
siderable quantity, since 404,378 cwt. were exported from Calcutta annually during the 
period 1896-1901. 
The most satisfactory progress is shown by coal-mining in India, to which attention has 
already on several occasions been drawn in this Journal, the output having increased from 
3.540.000 tons in 189510 6,118,000 tons in 1900. Indian coal is now being extensively 
used for industrial purposes, excepl in Bombay, which is too remote from the coalfields, 
and is still therefore dependent upon external sources for fuel. 
The output of iron ores is still very small, and iron is so far only smelted in the 
Raniganj district of Bengal, where it occurs in close proximity to coal ; in this neighbour- 
hood 57,000 tons of iron were manufactured in 1900, the total production in India being 
63.000 tons. 
It does not appear to be possible to further develop the Indian iron industry on 
the present lines, and the smelting of this metal will probably only be successful when 
carried on with large capital on a sufficiently extensive scale to enable the smelters to 
secure advantageous transport and freight rates. 
A considerable amount of gold is produced in Mysore, the output now exceeding 
500.000 ounces per annum. Small quantities are also found in the Nizam’s dominions, and 
in the rivers of Northern India, the total production for 1900 being 513,266 oz., valued at 
over two millions sterling. 
Petroleum is worked in Burma and Assam, the former produced 37,000,000 gallons 
last year, and the latter 1,000,000 gallons. This output is, however, not sufficient to meet 
the total demand in India, and a further 72 million gallons were obtained from Russia and 
the United States. 
The foregoing include the principal minerals worked in India, but mica, corundum, 
manganese ore and tinstone are also found and exported in small quantities, whilst con- 
siderable quantities of precious stones, in particular the jade and rubies of Upper Burma, 
are sent abroad. 
THE MAGNETIC IRON SAND OF THE ST. LAWRENCE. 
The deposits of magnetic iron sand occurring on north shore of the river St. Lawrence 
have been known from very early times, and were worked from 1867 to 1S75 by the 
“ Moisic Iron Co.” This company bought large tracts of land in the vicinity of Moisic 
and built there eight bloomary furnaces. The ore was first concentrated by means of 
magnets supplied with sand from an endless table or travelling band, and reduced in the 
furnace by means of charcoal as fuel. The blooms produced were exported to the United 
States, but the increased duty imposed in 1875 caused the company to close their works, and 
since that time this ore has not been utilized. 
The most important deposits occur at Natashquan, Moisic, and St. Jean. The deposit 
of St. John river extends from its mouth, six miles to the north-east. It is 2 to 10 inches in 
thickness, the richest part occurring at Point Noire, four miles from the river St. John. The 
Natashquan deposit extends from the mouth of river so-named eastward for about 20 miles, 
and there is in sight between low water mark and the timbered ground a strip of sand from 
100 feet to 400 feet wide, with dunes ranging from 5 to 50 feet in height. The thickness of 
the deposit varies from one inch to two feet on level ground, and contains from 20 to 95 per 
cent, of iron sand, while the dunes would give from 40 to 60 per cent. 
Mr. Obalski considers that these deposits have been formed by the disintegration of 
ferruginous rocks, such as anorthosites of the Laurentian series, by the seas of past geological 
periods which brought about a concentration of the product of disintegration according to 
density. The sand, besides magnetite, contains ilmenite, garnets and quartz, from which it 
can be almost completely separated by means of magnetic concentrators. The following 
analyses show the competition of this ore : — 
Moisic. Natashquan. 
Raw. 
Concentrated, 
Concentrated. 
per cent. 
per cent. 
per cent. 
per cent, 
Metallic iron 
55 ’ 2 3 
70*01 
71 *94 
69*78 
Silica 
— ■ 
— 
0*22 
0*321 
Sulphur 
. — 
traces 
0*026 
0*011 
Phosphorus 
. - — • 
0*03 
0*030 
0*015 
Titanium - 
9-6 
nil. 
0*420 
o*S6o 
