■006 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [January 28, 1871. 
composed ; they are of a dark green colour, and measure 
about inches. The flowers resemble those of the 
orange, and emit a strong perfume ; the fruit is about 
the size of a small lemon; it is almost of the same shape 
and colour. The interior consists of a red pulpy sub¬ 
stance, containing an innumerable quantity of small 
seeds somewhat larger than those of the fig. The rind 
of the fruit is of the consistency of that of an apple. Of 
this fruit the West Indians make several kinds of pre¬ 
serves,—the guava jelly, stewed guava, quake pear, and 
marmalade; the most lucrative is the guava jelly; the 
fruit is often eaten in its raw condition. The negroes 
are so fond of it that they are very wary and diligent in 
guarding the trees from robbery when they are bearing 
fruit. 
The guava jelly is obtained by boiling the guavas 
with sugar and spices; and, after expressing the juice 
through a cloth, it is left to cool. Of course it undergoes 
minor processes, which I omit, they being inappropriate 
to the object of this paper. 
The jelly is frequently bottled, but oftener it is put 
into small cylindrical boxes made of laminated pine 
board. A great quantity of this comfit is manufactured 
in Cuba, where it is termed “ Jalea de guayaba,” which 
is exported to the United States and Europe. Notwith¬ 
standing- that a good deal is made in the smaller islands, 
they import quite a quantity of the Cuban jelly. 
After the juice has been expressed from the guava, 
there remain the skins and the pulp containing the 
seeds; the latter is stewed and bottled, and it constitutes 
the stewed guava. This is generally partaken of with 
milk. 
The skins are converted into the delicacy termed 
“ quake pear,” by a process varying slightly from the 
foregoing. 
The guava marmalade is not frequently made. It 
consists of the guava grated and prepared in a peculiar 
manner. 
Of the before-mentioned preserves, the marmalade is 
preferred by most connoisseurs. The small seeds in the 
stewed guava are very objectionable, the more so if one 
is subject to toothache, as they get into the cavities of 
decayed teeth, causing a great deal of suffering. 
The natives of the West Indies are great herbalists; 
they convert almost any plant into medicine of some 
kind or other, and they have discovered several medici¬ 
nal properties in the guava-tree and its complementary 
portions; what they are, I cannot pretend to say. 
There is no distinction made between the name of the 
tree and that of the fruit in English, both being guava; 
the French term the tree goyavier , and the fruit goyavc. 
Their respective terms in the Creole patois are gyan- 
baum and gyan. — Druggists' Circular and Chemical Ga¬ 
zette. 
CHEMICAL EXAMINATION OF CONDENSED 
MILK.* 
The British Medical Journal reports the following re¬ 
sult of an analysis of the contents of a tin of Newnham’s 
Condensed Milk:— 
Water . . . 
. . . 19-0 
Caseine . . 
. . . 10-0 
Ash .... 
Fat ) 
Milk-Sugar > 
• . . 690 
Cane-Sugar ) 
100-0 
The water was determined by drying at 212 ° F. The 
caseine was determined directly, the result being verified 
by the employment of Wanklyn, Chapman and Smith’s 
ammonia process. The ash was determined by ignition. 
There appeared to be about as much fat as caseine. 
From the analysis it follows that the degree of condensa- 
* See ante , No. 6, p. 89. 
tion of Newnham’s Condensed Milk is between three and 
four; that is to say, one pound of the condensed milk 
contains the solid constituents of from three to four 
pounds of fresh milk. 
ANALYSIS OF MILK. 
In making examinations of milk for sanitary or com¬ 
mercial purposes, it is customary to use determinations 
of specific gravity as indices of the strength of milk. It 
is, however, recognized that owing to the circumstance 
of cream being lighter than water, whilst skimmed milk 
is heavier, the indication of strength afforded by a 
determination of specific gravity is not very precise. 
Obviously, if, in addition to the specific gravity, the per¬ 
centage of cream were taken, a connection could be ap¬ 
plied so as to rectify the indication of strength derived 
from specific gravity. In the course of an examination 
of milk undertaken for the Milk Journal , the observation 
was made that there is another source of inaccuracy 
hitherto quite unsuspected. Skimmed milk consists 
mainly of water, caseine milk, sugar and a small quan¬ 
tity of mineral salts. Now, the exact molecular condi¬ 
tion of the caseine influences the specific gravity of milk. 
In other words, samples of milk of the same strength 
will vary in specific gravity according to the exact mole¬ 
cular condition of the caseine. Especially are these 
changes in condition brought out if milk be kept for a 
while. This is illustrated by the following examples. 
We do not intend on this occasion to enter fully into 
the subject of milk analysis, but we may state that plans 
commonly adopted are of little worth. We have had to 
notice the untrustworthiness of specific gravity determi¬ 
nations of milk,—that is to say, the danger of judging of 
the strength of milk by its specific gravity. To be of 
any value at all, the specific gravity determination must 
be made whilst the sample of milk is very fresh. After 
milk has been kept for two or three days, even in a closed 
vessel, its specific gravity falls in a very remarkable 
manner. The following examples exhibit this in an ex¬ 
treme form. The specimens of milk had been kept in 
corked bottles for four days:— 
Sp. gr. at Percentage of Percentage 
60° F. Solids dry, at 212° F. of Ash. 
Sample a . 1-0004 . . i 1*34 . . 0-94 
„ b . 0-9960 . . 10-48 . . 0-75 
„ c . 1-0184 . . 8-92 . . 0-66 
Showing that the highest specific gravity sometimes ac¬ 
companies the lowest percentage of solids. The reason 
of this want of correspondence between specific gravity 
and solid contents we have already explained. Mean¬ 
while, in judging of the strength of milk, it is proposed 
to adhere to the method of evaporating to drjmess in the 
water-bath, and weighing the residue.— Milk Journal. 
THE HEAT DEVELOPED IN THE COMBINATION 
OF ACIDS AND BASES.* 
BY THOMAS ANDREWS, M.D., F.R.S., HON. F.R.S.E., 
Vice-President of Queen's College , Belfast. 
In a paper communicated to the Royal Irish Academy 
in 1841, I gave an account of a large number of experi¬ 
ments on the heat disengaged when acids and bases, 
taken in the state of dilute solution, enter into combina¬ 
tion, and when bases, insoluble in water, are dissolved in 
dilute acids. The following general conclusions or laws 
were deduced from those experiments:— 
Law 1 .-—The heat developed in the union of acids and 
bases is determined by the base and not by the acid, the 
same base producing, when combined with an equivalent 
of different acids, nearly the same quantity of heat; but 
different bases, different quantities. 
* From the ‘ Transactions of the Royal Society of Edin¬ 
burgh,’ Session 1869-70. 
