REMARKS ON LEMON-JUICE AND ITS PRESERVATION. 
161 
until the mass is thoroughly melted, when it is raked out into a mould ; on cool¬ 
ing, the loaf is turned out, and forms “ black ash.” The chemical changes 
which take place when sulphate of soda is fused with chalk and coal are, first, 
the deoxidation of the “salt-cake” and its conversion into sulphide of sodium 
with evolution of carbonic oxide ; secondly, the formation of carbonate of soda 
and sulphide of calcium, the latter being rendered insoluble by the excess of 
chalk employed. The “soda-ash” is afterwards broken up and exhausted with 
warm water; it is then evaporated, and while hot is run into pans capable of 
holding a hundred and fifty gallons of liquid, and about one ton of crystallized 
carbonate of soda. The liquid cools in the course of four or five days. The 
crust of one of these pans was broken and a mass of large bright clear crystals 
exhibited to view. 
Carbonate of magnesia is manufactured here, but by a very different process 
from that usually seen in the laboratory. Dolomite, the double carbonate of 
magnesia and lime, is powdered and exposed to a red-heat for two or three 
hours, by which means the carbonate of magnesia is decomposed. It is then 
mixed with water and introduced into an iron cylinder, into which carbonic 
acid is forced under pressure, the carbonate of magnesia dissolves out as bicar¬ 
bonate, leaving the carbonate of lime behind; the clear solution when boiled 
deposits the carbonate of magnesia, which is drained and dried on stoves at a 
low temperature. 
Mr. Bell has rendered service to science by collecting and preparing a consi¬ 
derable quantity of that interesting new metal—thallium—discovered by Mr. 
Crookes, and a bar of which was exhibited at the soiree. Thallium is contained 
in the iron pyrites used in making sulphuric acid ; it sublimes as a sulphuret, and 
is collected with the fiue-dust from the tubes through which the sulphurous va¬ 
pours pass before going into the leaden chambers. 
After seeing the process for the manufacture of sulphuric acid, we passed on 
to that of oxychloride of lead ; this is made by decomposing a solution of chlo¬ 
ride of lead with lime-water, and is used largely by painters in the place of 
white-lead. 
At these works very great care is bestowed in the condensation of the gases, 
for notwithstanding the large volumes that are given off. we were particularly 
struck with the purity of the air. 
338, Oxford Street. 
REMARKS ON LEMON-JUICE AND ITS PRESERVATION. 
The fact that prescriptions, ordering alkaline mixtures to be taken effervescing 
with lemon-juice, are often accompanied by instructions that “ the lemon-juice is 
not to be sent,” is both unpleasant and unprofitable. Unpleasant, as indicating 
suspicion on the part of the prescriber that the dispenser will not faithfully dis¬ 
charge his duty, in sending exactly what is prescribed, and thus weakening the 
confidence of the patient; unprofitable, as it deprives the pharmaceutist of a 
portion of his legitimate profit. Now as there can be no effect without a cause, 
so there must be a reason why the above instructions are so frequently received, 
and it appears to be just this :—Lemon-juice will not keep for any length of time 
if simply strained and bottled. Pereira and Royle, after stating this, give for¬ 
mula} fur its artificial preparation, and there can be no doubt that a substitute so 
prepared is largely used. This, in dispensing, is about as justifiable as extempo¬ 
rizing Inf. Cinchonse by an aqueous solution of quinine and cinchonine. Yet 
who would countenance the latter? Royle also states that “druggists in this 
country preserve it (the fresh juice) by adding of spirit of wine, and filtering 
off the mucilage.” Spirit is highly objectionable in cases for which effervescing 
