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as crystal-ice. I have seen ice of this sort exposed for sale in a seaside town, and recommended to
the attention of the public as being germ free. Further, I have been informed that oysters have
been served with a piece of distilled-water-ice upon each oyster; the accompanying menu contained
an assurance that the ice was made from sterlised water; reference to the purity of the oyster was
apparently regarded as a work of supererogation.
A stimulus to the use of distilled water has been furnished by the fact that the crystal clearness
of the resulting ice renders it especially attractive. If tap water is frozen in the ordinary way
the ice is full of minute air bubbles and is quite opaque and as unsightly as, though probably far
purer than, ordinary natural " snow ice." In order to overcome this difficulty the water may be
agitated during the process of freezing, and the ice free from bubbles can be thus produced.
The opacity of ordinary artificial ice has militated greatly against its popularity in the past.
The idea has been entertained that the lack of transparency was due to chemicals, and the use of
the expression " ammonia process " appears to have led to the suggestion that ammonia was
actually introduced into the ice itself. Fishmongers have, for instance, complained that artificial
ice turned their fish black, and much misapprehension on the subject has undoubtedly existed.
Artificial ice, of course, contains no chemicals. The principle underlying the use of ammonia or
carbonic acid is simply that the gas, when allowed to expand, absorbs heat, and this power of
taking away heat is utilised to cool brine1, which circulates in pipes around the cells or receptacles
in which the water to be frozen is placed. There is, of course, a possibility that the brine may
escape from the pipes and contaminate the freezing water, but if this happens the resulting ice is,
I was assured, of necessity, so discoloured and unsightly as to make it impossible for it to be sold.
Another alleged disadvantage is that artificial does not possess the lasting power of natural
ice. In a note in " Cold Storage" for August, 1903, attention is called to the argument advanced
by the " Chicago Chronicle " to this effect. " Hygeia ice " (i.e., manufactured ice) never steams or
gives off, according to the American journal, that "live frigidity which is the essence of coolth."
" Lake ice," on the other hand, " smokes and radiates, lives, and dies," while manufactured ice
"cannot die because it is dead in the beginning." The "Chicago Chronicle" continues, "Air is
life; hygeia ice has no air in it: lake ice is full of air." It will be recollected that, according to
Dr. Prudden and other bacteriologists, "bubbly ice" is particularly impure. Moreover, one of the
great difficulties with regard to manufactured ice has been seen to be the fact that it is opaque,
owing to contained air bubbles. Indeed, there appear to be more things deserving study in connection
with the " essence of coolth" than are dreamt of in the philosophy of the " Chicago
Chronicle." One very important consideration which muBt not be lost sight of is the size of the
blocks compared. Ordinary Norway ice averages from twenty to twenty-four inches in thickness,
and a block cut from such ice presents less surface in proportion to its bulk than does the average
block of artificial ice which, as a rule, is only about half that thickness. The reason lies, of
course, in the fact that increase in thickness means increased time in freezing. I was informed at
an ice factory that the first four inches frozen became congealed in twenty-four hours, but after
that the average time occupied in freezing the rest of the slab was twenty-four hours per inch, and with
further increase in thickness of the slab increasing intervals of time would, of course, be required.
That the staying power of ice depends upon the size of the ice-blocks will be appreciated by
considering that if a block of ice one foot cube be divided into pieces of one inch cube, the total
superficial area exposed in the small cubes taken altogether is twelve times as great as in the case
of the large cube. Such a consideration makes it clear that it is not worth the while of the ice
merchant to store ice which is only a few inches thick, and indeed, since 1881, canal and river ice
have not, I am informed, been stored in London on any considerable scale. Hence, again, blocks
of artificial ice, twelve inches or less in the smallest dimension, and Norway ice when the winter
has been mild and the ice is, only it may be, fourteen inches thick, do not keep as well as blocks
which are, say, two feet at least in the smallest dimension.
There are three different systems of making artificial ice which are practised at the present
time.2 In the "can system" tapered blocks from six to eight inches thick are frozen in cans suspended
in a tank containing refrigerated brine kept at a temperature of about 14° F. In the
" plate system " large plates of ice, ten or eleven inches thick are produced. A tank is divided by
vertical partitions within which cold brine circulates, the interspaces left between these partitions
are some 8 to 12 ft. long, 6ft. deep, and from 29 to 27 in. wide. The ice forms on each side of the
partitions in which the brine circulates, and freezing is allowed to go on until the ice is from 6 to
10 in. thick. Sometimes the partitions are 10 or 12 in. apart, and freezing is continued until the
ice, forming on one side of a partition, meets the ice advancing from the next partition and makes
with it a coherent mass. In this case, however, air bubbles and impurities are apt to be frozen in ;
in other words, the ice has a "core." In the " cell system" blocks of approximately cubical shape
are produced.
Artificial ice may be of three kinds—ordinary opaque ice, agitated ice (the water being
deprived of most of its air by agitation), and distilled water ice (the water frozen being distilled
water, and the ice formed consequently free from air bubbles, and clear as crystal.)
It remains to say a few words with regard to cold storage as carried on in London at the
present time, and of course the hygienic aspect of this subject alone will be here referred to, and it
may be premised that very little appears to be known with regard to the question, the ground
being at the present time practically unbroken.
1 The circulating brine is capable of carrying a lower temperature than 32 deg. F. Chloride of calcium is the
salt usually employed in the brine of refrigerating works ; it produces a greater refrigerating effect, and is less apt
to clog the pipes than sodium-chloride brine.
2 Further details with regard to these systems will be found in " Mechanical Refrigeration," by Hal Williams,
Whittaker & Co., 1903.