that family No. 1 purchased their bread at the bakery at a cost of $
1.00, while the bread of family No. 2 was home-made, skim milk being
used in its preparation, the flour, milk, yeast, and shortening costing
about 55 cents. Family No. 1 consumed 10 pounds of expensive steaks,
family No. 2 consumed the same number of pounds, a portion being cheaper
cuts. Instead of the 20 pounds of roast or similar beef used by family
No. 1, only one half as much and cheaper cuts as boiling pieces, stew,
rump roast, etc., were used by family No. 2; 5 pounds of beans and 5
pounds of cheese taking the place of some of the meat. Family No. 1
consumed 4 pounds of high-priced cereal breakfast foods, supposing they
contained a larger amount of nutrients than were actually present. In
place of the 4 pounds of high-priced cereal breakfast foods of family
No. 1, family No. 2 used 5 pounds of oatmeal purchased in bulk. Family
No. 1 bought their cake and pastry for $3.00, while those of family No.
2 were home made and cost $1.00. Family No. 2 used 2 pounds less butter
per week because of the preparation and use of home-made shortening from
beef suet and milk. They also purchased a smaller amount of tea, coffee,
and spices than family No. 1. Family No. 2 consumed a larger quantity of
less expensive fruits and vegetables than family No. 1, who ate 75
cents' worth of mushrooms with the idea that they contained as much
protein as meat, but analyses show that mushrooms contain no more
nutrients than potatoes and similar vegetables. In place of the celery
and oranges, apples and prunes were used by family No. 2. The same
amount of potatoes was used by each. Fifty cents was spent for milk by
family No. 1 and $1.00 by family No. 2. The total amount expended for
food by family No. 1 was $23.45, while family No. 2 purchased a greater
variety of foods for $11.30, as well as foods containing more nutrients.
The approximate amounts of nutrients in the foods purchased by the two
families are given in the following table, from which it will be
observed that family No. 2 obtained a much larger amount of total
nutrients and was better fed at considerably less expense than family
No. 1.
NUTRIENTS IN FOODS CONSUMED.--FAMILY NO. 1
=============================================
|PROTEIN| FAT |CARBOHYDRATES
| LB. | LB. | LB.
-------------------------|-----|-------------
20 lb. bread | 1.98 | 0.28| 11.42
10 lb. loin steak| 1.59 | 1.76| --
20 lb. rib roast | 2.68 | 4.26| --
4 lb. cereals | 0.42 | 0.06| 2.75
8 lb. butter | 0.04 | 6.80| --
25 lb. potatoes | 0.45 | 0.03| 3.83
20 lb. milk | 0.70 | 0.80| 1.00
|-------|-----|-------------
| 7.86 |13.99| 19.00
=============================================
FAMILY NO. 2
=====================================================
|PROTEIN| FAT |CARBOHYDRATES
| LB. | LB. | LB.
-------------------------|-------|-----|-------------
15 lb. flour | 1.89 | 0.12| 11.15
5 lb. skim milk | 0.16 | 0.01| 0.26
10 lb. round steak | 1.81 | 1.26| --
10 lb. beef | 1.32 | 2.02| --
5 lb. cheese | 1.40 | 1.75| --
5 lb. oatmeal | 0.78 | 0.36| 3.40
6 lb. butter | 0.03 | 5.10| --
3 lb. shortening | -- | 2.55| --
3 lb. prunes | 0.03 | -- | 0.60
25 lb. apples | 0.12 | -- | 2.50
25 lb. potatoes | 0.45 | 0.03| 3.83
40 lb. milk | 1.44 | 1.60| 1.90
5 lb. beans | 1.12 | -- | 3.00
-------------------------|-------|-----|------------------
| 10.55 |14.80| 26.64
-------------------------|-------|-----|------------------
Difference in nutrients |
in favor of family No. 2,|
consuming the cheaper |2.69 0.81 7.64
combination of foods |
=====================================================
255. Food in its Relation to Mental and Physical Vigor.--When the body
is not properly supplied with food, the best results in the form of
productive work cannot be secured. There is a close relationship between
the nature of the food consumed and mental activity, also ability to
satisfactorily perform physical labor. "The productive power of the
individual as well as of the nation depends doubtless upon many factors
other than food, such as race, climate, habit, etc., but there is no
gainsaying the fact that diet has also a profound and direct influence
upon it."[83]
If the body is diseased, it cannot make the right uses of the food, and
often the food is blamed when the trouble is due primarily to other
causes. The fact that a diseased digestive tract is unable to utilize
some foods is no valid reason why these foods should be discarded in the
dietary of persons in normal health, particularly when the food is in no
way responsible for the disease.
Some diseases are most prevalent in the case of a restricted diet. A
change in the dietary of the Japanese navy greatly improved the health
of the sailors.
"The prevalence of kakke or beriberi in the navy turned the
attention of many medical specialists toward the problem of
nutrition.... It was generally believed that there was some very
close connection between the disease and the rice diet.... One
outcome of these investigations was the passage of the food supply
act of the navy in 1884. The ration provided in accordance with
this act was sufficient to furnish an abundance of protein and
energy.... Following the change of ration in 1884, the prevalence
of the disease was very materially diminished, and at the end of
three years cases of kakke were practically unknown among the
marines."[83]
256. Dietary Studies in Public Institutions.--Dietary studies in
public institutions, as prisons, and asylums for the insane, show that
it is possible to secure greater variety of food containing a larger
amount of nutrients, and even at a reduction in cost.[84] In such
institutions it is important that the food should be not only ample in
amount, but wholesome and nutritious, as many of the inmates respond
both physically and mentally to an improved diet. For humanitarian as
well as economic reasons institutional dietetics should more generally
be placed under the supervision of skilled dietists.
CHAPTER XVIII
RATIONAL FEEDING OF MAN
257. Object.--Rational feeding of man has for its object the
regulation of the food supply in accord with the demands of the body. It
is based upon the same principles as the rational feeding of animals; in
each, the best results in the way of health, amount of labor performed,
and economy are secured when the body receives nutrients sufficient for
the production of heat and energy and for the repair of worn-out
tissues. Rational feeding is simply regulation of the food, both as to
kind and amount, to meet the needs of the body.[72]
258. Standard Rations.--In human feeding, as in animal feeding, it is
not possible to lay down hard and fast rules as to the quantity of
nutrients required for a standard ration.[85] As stated in the chapter
on Dietary Studies, such standards have been proposed, but they are to
be considered as tentative rather than absolute, for the amount of food
required by different persons must necessarily vary with the
individuality. While it is impossible to establish absolute standards,
any large variation from the provisional standards usually results in
lessened ability to accomplish work, ill health, or increased expense.
259. Amounts of Food Consumed.--The approximate amounts of some food
articles consumed per day are as follows:
===================================
| RANGE | APPROXIMATE
| |AMOUNT IN LBS.
--------|--------------------------
Bread |6 to 14 oz.| 0.50
Butter |2 to 5 oz.| 0.12
Potatoes|8 to 16 oz.| 0.75
Cheese |1 to 4 oz.| 0.12
Beans |1 to 4 oz.| 0.12
Milk |8 to 32 oz.| --
Sugar |2 to 5 oz.| 0.20
Meats |4 to 12 oz.| 0.25
Oatmeal |1 to 4 oz.| 0.12
===================================
In the calculation of rations it is desirable that the amount of any
food article should not exceed that designated, unless for some special
reason it has been found the food can consistently be increased. The
amount of nutrients given in dietary standards is for one day, and the
nutrients may be divided among the three meals as desired. It is to be
noted that, ordinarily, the foods which supply carbohydrates are flour,
corn meal, cereal products, potatoes, beans, sugar, and milk; those
which supply fat are milk, butter, lard, and meats; and those which
supply protein in liberal amounts are beans, cheese, meats, oatmeal,
cereals, bread, and milk.
260. Average Composition of Foods.--The amounts of nutrients in foods
are determined from the average composition of the foods. These figures
for average composition are based upon analyses of a large number of
samples of food materials.[7] In individual cases it will be found that
foods may vary from the standards given; as for example, milk may
contain from 2.5 to 5 per cent of fat, while the protein and fat of
meats vary appreciably from the figures given for average composition.
With the cereals and vegetable foods, variations from the standards are
small. In the table, the composition of the food as purchased represents
all of the nutrients in the food, including those in the refuse,
trimmings, or waste, while the figures for the edible portion represent
the nutrients in the food after deducting what is lost as refuse. In
making calculations, the student should use the figures given for the
foods as purchased, unless the weights are of the edible portion only.
The figures in the table are on the basis of percentage amounts, or
nutrients in 100 pounds of food. By moving the decimal point two places
to the left, the figures will represent the nutrients in one pound, and
if this is multiplied by the number of pounds or fraction of a pound
used, the quantity of nutrients is secured. For example, suppose bread
contains 9.5 per cent of protein and 56 per cent of carbohydrates, 1
pound would contain 0.095 pound of protein, 0.56 pound of
carbohydrates; and 0.5 of a pound would contain approximately 0.05 pound
of protein and 0.28 pound of carbohydrates. In calculating rations, it
is not necessary to carry the figures to the third decimal place.
[Illustration: FIG. 60.--FOOD ARTICLES FOR A HUMAN RATION.]
261. Example of a Ration.--Suppose it is desired to calculate a ration
for a man at light muscular work. First, note the requirements in the
way of nutrients in the table "Dietary Standards," Section 246. Such a
ration should supply approximately 0.22 pound each of protein and fat,
and 0.77 pound of carbohydrates, and should yield 2800 calories. A trial
ration is made by combining the following:
==========================================================
| Pound
Bread | 0.50
Butter | 0.12
Potatoes | 0.75
Milk | 1.00
Sugar | 0.12
Beef | 0.25
Ham | 0.20
Oatmeal | 0.12
Eggs | 0.25
==========================================================
The quantities of nutrients in these food materials are approximately as
follows:
RATION FOR MAN AT MODERATE WORK
===================================================================
| | PROTEIN | FAT | C.H. |
| LB. | LB. | LB. | LB. | CALORIES
-------------------------+------+---------+------+------+----------
Bread | 0.50 | 0.05 | 0.01 | 0.29 | 653
Butter | 0.12 | -- | 0.10 | -- | 432
Potato | 0.75 | 0.01 | -- | 0.12 | 244
Milk | 1.00 | 0.04 | 0.04 | 0.05 | 323
Sugar | 0.12 | -- | -- | 0.12 | 192
Beef (round) | 0.25 | 0.05 | 0.03 | -- | 218
Ham | 0.20 | 0.03 | 0.07 | -- | 331
Oatmeal | 0.12 | 0.02 | 0.01 | 0.08 | 223
Eggs | 0.25 | 0.03 | 0.03 | -- | 164
Squash | 0.20 | -- | -- | 0.01 | 25
|------+---------+------+------+----------
| | 0.23 | 0.29 | 0.67 | 2805
===================================================================
It is to be noted that this ration contains approximately the amount of
protein called for in the standard ration, while the fat is slightly
more and the carbohydrates are less. The food value of the ration is
practically that called for in the standard. This ration is sufficiently
near the standard to supply the nutrient requirements of a man at light
muscular work. To supply palatability, some fruit and vegetables should
be added to the ration. These will contribute but little to the nutrient
content, but are necessary in order to secure health and the best
returns from the other foods, and as previously stated, they are not to
be estimated entirely upon the basis of nutrient content. A number of
food articles could be substituted in this ration, if desired, either in
the interests of economy, palatability, or personal preference.
262. Requisites of a Balanced Ration.--Reasonable combinations of
foods should be made to form balanced rations.[2] A number of foods slow
of digestion, or which require a large amount of intestinal work, should
not be combined; neither should foods which are easily digested and
which leave but little indigestible residue. After a ration has been
calculated and found to contain the requisite amount of nutrients, it
should be critically examined to see whether or not it fulfills the
following requirements:
1. Economy and adaptability to the work required.
2. Necessary bulk or volume.
3. Desired physiological influence of the foods upon the digestive
tract, whether constipating or laxative in character.
4. Ease of digestion.
5. Effect upon health. It is recognized that there are foods
wholesome and nutritious, that cannot be used by some persons,
while with others the same foods can be consumed with impunity.
As explained in the chapter on Dietary Studies, the nutrients should be
supplied from a number of foods rather than from a few, because it is
believed the various nutrients, particularly the proteins, are not
absolutely identical from all sources, or equal in nutritive value.
EXAMPLES
1. Calculate a ration for a man with little physical exercise.
2. Calculate a ration for a man at hard muscular labor, and give the
approximate cost of the ration.
3. Calculate the amounts of food and the nutrient requirements for a
family of seven for 10 days; five of the family to consume 0.8 as much
as an adult. Calculate the cost of the food; then calculate on the same
basis the probable cost of food for one year, adding 20 per cent for
fluctuation in market price and additional foods not included in the
list.
4. Weigh out the food articles used in problem No. 2, and apportion them
among three meals.
CHAPTER XIX
WATER
263. Importance.--Water is one of the most essential food materials.
It enters into the composition of the body, and without it the nutrients
of foods would be unavailable, and life could not be sustained. Water
unites chemically with various elements to form plant tissue and
supplies hydrogen and oxygen for the production of organic compounds
within the leaves of plants. In the animal economy it is not definitely
known whether or not water furnishes any of the elements of which the
tissues are composed, as the food contains liberal amounts of hydrogen
and oxygen; it is necessary mainly as the vehicle for distributing
nutrients in suspension and solution, and as a medium in which chemical,
physical, and physiological changes essential to life processes take
place. From a sanitary point of view, the condition of the water supply
is of great importance, as impure water seriously affects the health of
the consumer.[87]
264. Impurities in Water.--Waters are impure because of: (1) excessive
amounts of alkaline salts and other mineral compounds; (2) decaying
animal and vegetable matters which act chemically as poisons and
irritants, and which may serve as food for the development of
objectionable bacterial bodies; and (3) injurious bacteria. The most
common forms of impurities are excess of organic matter and bacterial
contamination. The sanitary condition of water is greatly influenced by
the character of the soil through which it flows and the extent to which
it has been polluted by surface drainage.[88]
[Illustration: FIG. 61.--DIRT AND IMPURITIES IN A SURFACE WELL WATER.]
265. Mineral Impurities.--- The mineral impurities of water are mainly
soluble alkaline and similar compounds dissolved by the water in passing
through various layers of soil and rock. When water contains a large
amount of sodium chloride, sodium sulphate or carbonate, or other
alkaline salts, it is termed an "alkali water." Where water passes
through soil that has been largely formed from the decay of rocks
containing alkaline minerals, the water dissolves some of these minerals
and becomes alkaline. The kind of alkali determines the character of the
water; in some cases it is sodium carbonate, which is particularly
objectionable. The continued use of strong alkali water causes digestion
disorders, because of the irritating action upon the digestive tract.
Hard waters are due to the presence of lime compounds. In regions where
limestone predominates, the carbon dioxid in water acts as a solvent,
producing hard waters. Waters that are hard on account of the presence
of calcium carbonate give a deposit when boiled, due to liberation of
the carbon dioxid which is the material that renders the lime soluble.
Calcium sulphate, or gypsum, on the other hand, imparts permanent
hardness. There is no deposit when such waters are boiled. A large
number of minerals are found in various waters, often sufficient in
amount to impart physiological properties. Water that is highly charged
with mineral matter is difficult to improve sufficiently for household
purposes. About the only way is by distillation.[89]
266. Organic Impurities.--Water that flows over the surface of the
ground comes in contact with animal and vegetable material in various
stages of decay, and as a result some is dissolved and some is
mechanically carried along by the water. After becoming soluble, the
organic matter undergoes further chemical changes, as oxidation and
nitrification caused by bacteria. If the organic matter contain a large
amount of nitrogenous material, particularly of proteid origin, a series
of chemical changes induced by bacterial action takes place, resulting
in the production of nitrites. The nitrifying organisms first produce
nitrous acid products (nitrites), and in the further development of the
nitrifying process these are changed to nitrates. The ammonia formed as
the result of the decomposition of nitrogenous organic matter readily
undergoes nitrification changes. Nitrates and nitrites alone are not
injurious in water, but they are usually associated with objectionable
bacteria and generally indicate previous contamination.[90]
267. Interpretation of a Water Analysis.--"Total solid matter"
represents all the mineral, vegetable, and animal matter which a water
contains. It is the residue obtained by evaporating the water to dryness
at a temperature of 212° F. Average drinking water contains from 20 to
90 grains per gallon of solid matter. "Free ammonia" is that formed as a
result of the decomposition of animal or vegetable matter containing
nitrogen. Water of high purity usually contains less than 0.07 parts
per million of free ammonia. "Albuminoid ammonia" is derived from the
partially decomposed animal or vegetable material in water. The greater
the amount of nitrogenous organic impurities, the higher the albuminoid
ammonia. A good drinking water ought not to contain more than 0.10 part
per million of albuminoid ammonia. An abnormal quantity of chlorine
indicates surface drainage or sewage contamination, or an excess of
alkaline matter, as common salt. Nitrites should not be present, as they
are generally associated with matter not completely oxidized. Nitrites
are usually considered more objectionable than nitrates; both are
innocuous unless associated with disease-producing nitroörganisms.
268. Natural Purification of Water.--River waters are sometimes dark
colored because of large amounts of dissolved organic matter, but in
contact with the sun and air they gradually undergo natural purification
and the organic matter is oxidized. However, absolute reliance cannot be
placed upon natural purification of a bad water, as the objectionable
organisms often have great resistive power. There is no perfectly pure
water except that prepared in the chemical laboratory by distillation.
All natural waters come in contact with the soil and air, and
necessarily contain impurities proportional to the extent of their
contamination.
269. Water in Relation to Health.--There are many diseases, of which
typhoid fever is a type, that are distinctly water-born. The typhoid
bacilli, present in countless numbers in the feces of persons suffering
or convalescent from typhoid fever, find their way into streams, lakes,
and wells.[91] They retain their vitality, and when they enter the
digestive tract of an individual, rapidly increase in numbers. Numerous
disastrous outbreaks of typhoid fever have been traced to contamination
of water. Coupled with the sanitary improvement of a city's water
supply, there is diminution of typhoid fever cases, and a noticeable
lowering of the death rate. Many cities and villages are dependent for
their water upon rivers and lakes into which surface drainage finds its
way, with all contaminating substances. Mechanical sedimentation and
filtration greatly improve waters of this class, but do not necessarily
render them entirely pure. Compounds of iron and aluminium are sometimes
added in small amounts, under chemical supervision, to such waters to
precipitate the organic impurities. Spring waters are not entirely above
suspicion, as oftentimes the soil through which they flow is highly
polluted. All water of doubtful purity should be boiled, and there are
but few natural waters of undoubted purity. There is no such thing as
absolutely pure water in a state of nature. The mountain streams perhaps
approach nearest to it where there are no humans to pollute the banks;
but then there are always the beasts and birds, and they, too, are
subject to disease. There are very few waters that at some time of the
year and under some conditions are not contaminated with
disease-producing organisms. No matter how carefully guarded are the
banks of lakes furnishing the water supply of cities, more or less
objectionable matter will get in. In seasons of heavy rains, large
amounts of surface water enter the lakes, carrying along the filth
gathered from many acres of land drained by the streams entering the
lakes. Some of the most serious outbreaks of typhoid fever have come
from temporary contamination of ordinarily fairly good drinking water.
In general, too little attention is given to the purity of drinking
water. It is just as important that water should be boiled as that food
should be cooked. One of the objects of cooking is to destroy the
injurious bacteria, and they are frequently more numerous in the
drinking water than in the food.
The argument is sometimes advanced that the mineral matter present in
water is needed for the construction of the bone and other tissues of
the body, and that distilled water fails to supply the necessary mineral
matter. This is an erroneous assumption, as the mineral matter in the
food is more than sufficient for this purpose. When water is highly
charged with mineral salts, additional work for their elimination is
called for on the part of the organs of excretion, particularly the
kidneys; and furthermore, water nearly saturated with minerals cannot
exert its full solvent action.
In discussing the immediate benefits resulting from improvement of
water, Fuertes says:[92]
"Immediately after the change to the 'four mile intake' at Chicago
in 1893, there was a great reduction in typhoid. Lawrence, Mass.,
showed a great improvement with the setting of the filters in
operation in September, 1893; fully half of the deaths in 1894 were
among persons known to have used the unfiltered canal water. The
conclusion is warranted that for the efficient control of the death
rate from typhoid fever it is necessary to have efficient sewerage
and drainage, proper methods of living, and pure water. The reason
why our large cities, which are all provided with sewerage, have
such high death rates is therefore without doubt their continuance
of the filthy practice of supplying drinking water which carries in
solution and suspension the washings from farms, from the streets,
from privies, from pigpens, and the sewage of cities.... And also
we should recognize the importance of flies and other winged
insects and birds which feed on offal as carriers of bacteria of
specific diseases from points of infection to the watersheds, and
the consequent washing of newly infected matter into our drinking
water by rains."
There is a very close relationship between the surface water and that of
shallow wells. A shallow well is simply a reservoir for surface water
accumulations. It is stated that, when an improved system of drainage
was introduced into a part of London, many of the shallow wells became
dry, indicating the source from which they received their supply. Direct
subterranean connection between cesspools and wells is often traced in
the following way: A small amount of lithium, which gives a distinct
flame reaction, and a minute trace of which can be detected with the
spectroscope, is placed in the cesspool, and after a short time a
lithium reaction is secured from the well water.
Rain water is relied upon in some localities for drinking purposes. That
collected in cities and in the vicinity of barns and dwellings contains
appreciable amounts of organic impurities. The brown color is due to the
impurities, ammonium carbonate being one of these. There are also traces
of nitrates and nitrites obtained from the air. When used for drinking,
rain water should be boiled.
270. Improvement of Waters.--Waters are improved by: (1) boiling,
which destroys the disease-producing organisms; (2) filtration, which
removes the materials mechanically suspended in the water; and (3)
distillation, which eliminates the impurities in suspension and
solution, as well as destroys all germ life.
271. Boiling Water.--In order to destroy the bacteria that may be in
drinking water, it is not sufficient to heat the water or merely let it
come to a boil. It has been found that if water is only partially
sterilized and then cooled in the open air, the bacteria develop more
rapidly than if the water had not been heated at all. It should boil
vigorously five to ten minutes; cholera and typhoid bacteria succumb in
five minutes or less. Care should be taken in cooling that the water is
not exposed to dust particles from the air nor placed in open vessels in
a dirty refrigerator. It should be kept in perfectly clean,
tight-stoppered bottles. These bottles should be frequently scalded.
Great reliance may be placed upon this method of water purification when
properly carried out.
272. Filtration.--Among the most efficient forms of water filters are
the Berkefeld and Pasteur. The Pasteur filter is made of unglazed
porcelain, and the Berkefeld of fine infusorial earth (finely divided
SiO_{2}). Both are porous and allow a moderately rapid flow of water.
The flow from the Berkefeld filter is more rapid than from the Pasteur.
The mechanical impurities of the water are deposited upon the filtering
surface, due to the attraction which the material has for particles in
suspension. These particles usually are the sources of contamination and
carry bacteria. When first used, filters are satisfactory, but unless
carefully looked after they soon lose their ability to remove germs from
the water and may increase the impurity by accumulation. Small faucet
filters are made of porous stone, asbestos, charcoal, etc. Many of them
are of no value whatever or are even worse than valueless. Filters
should be frequently cleansed in boiling water or in steam under
pressure. Unless this is done, the filters may become incubators for
bacteria.
[Illustration: FIG. 62.--PASTEUR WATER FILTERS.]
273. Distillation.--When an unquestionably pure water supply is
desired, distillation should be resorted to. There are many forms of
stills for domestic use which are easily manipulated and produce
distilled water economically.[93] The mineral matter of water is in no
way essential for any functional purpose, and hence its removal through
distillation is not detrimental.
[Illustration: FIG. 63.--WATER STILL.]
274. Chemical Purification.--Purification of water by the use of
chemicals should not be attempted in the household or by inexperienced
persons. When done under supervision of a chemist or bacteriologist, it
may be of great value to a community. Turneaure and Russell,[94] in
discussing the purification of water by addition of chemicals, state:
"There are a considerable number of chemical substances that may be
added to water in order to purify it by carrying down the suspended
matter as well as bacteria, by sedimentation. Such a process of
purification is to be seen in the addition of alum, sulphate of
iron, and calcium hydrate to water. Methods of this character are
directly dependent upon the flocculating action of the chemical
added, and the removal of the bacteria is accomplished by
subsidence."
275. Ice.--The purity of the ice supply is also of much importance.
While freezing reduces the number of organisms and lessens their
vitality, it does not make an impure water absolutely wholesome. The
way, too, in which ice is often handled and stored subjects it to
contamination, and foods which are placed in direct contact with it
mechanically absorb the impurities which it contains. For cooling water,
ice should be placed around rather than in it. Diseases have frequently
been traced to impure ice. The only absolutely pure ice is that made
from distilled water.
276. Mineral Waters.--When water is charged with carbonic acid gas
under pressure, carbonated water results, and when minerals, as salts of
sodium, potassium, or lithium, are added, artificial mineral waters are
produced. Natural mineral waters are placed on the market to some
extent, but most mineral waters are artificial products and they are
sometimes prepared from water of low sanitary character. Mineral waters
should not be used extensively except under medical direction, as many
have pronounced medicinal properties. Some of the constituents are
bicarbonates of sodium, potassium, and lithium; sulphates of magnesium
(Epsom salts) and calcium; and chloride of sodium. The sweetened mineral
waters, as lemonade, orangeade, ginger ale, and beer, contain sugar and
organic acids, as citric and tartaric, and are flavored with natural or
artificial products. Most of them are prepared without either fruit or
ginger. Natural mineral waters used under the direction of a physician
are often beneficial in cases of chronic digestion disorders or other
diseases.
277. Materials for Softening Water.--The materials most commonly used
for softening water are sodium carbonate (washing soda), borax, ammonia,
ammonium carbonate, potash, and soda lye. Waters that are very hard with
limestone should have a small amount of washing soda added to them. Two
ounces for a large tub of water is the most that should be used, and it
should first be dissolved in a little water. If too much soda is used,
it is injurious, as only a certain amount can be utilized for softening
the water, and the excess simply injures the hands and fabric. When hard
limewater is boiled and a very little soda lye added, a precipitate of
carbonate of lime is formed, and then if the water is strained, it is
greatly improved for washing purposes. Borax is valuable for making some
hard waters soft. It is not as strong in its action as is sodium
carbonate. For the hardest water 1/4 pound of borax to a large tubful
may be used; most waters, however, do not need so much. Ammonia is one
of the most useful reagents for softening water. It is better than
washing soda and borax, because the ammonia is volatile and does not
leave any residue to act on the clothes, thus causing injury. For
bathing purposes, the water should be softened with ammonia, in
preference to any other material. Ammonia should not be poured directly
into hot water; it should be added to the water while cold, or to a
small quantity of cold water, and then to the warm water, as this
prevents the ammonia from vaporizing too readily. Ammonia produces the
same effect as potash or soda lye, without leaving a residue in the
garments washed. It is especially valuable in washing woolen goods or
materials liable to shrink. Waters which are hard with alum salts are
greatly benefited by the addition of ammonia. A little in such a water
will cause a precipitate to form, and when the water is strained it is
in good condition for cleaning purposes. Ammonium carbonate is used to
some extent as a softening and cleaning agent, and is valuable, as there
is no injurious effect upon clothing, because it readily volatilizes.
Caustic potash and caustic soda are sometimes employed for softening
water, but they are very active and are not adapted to washing colored
or delicate fabrics. They may be used for very heavy and coarse articles
that are greasy,--not more than a gram in a gallon of water. Bleaching
powder is not generally a safe material for cleansing purposes, as it
weakens the texture of clothing. After a contagious disease, articles
may be soaked in water containing a little bleaching powder and a few
drops of carbolic acid, followed by thorough rinsing and bleaching in
the sun. But as a rule formaline is preferable for disinfecting
clothing. It can be used at the rate of about one pound to 100 gallons
of water. Bleaching powder, caustic potash or soda, and strong soap are
not suitable for cleaning woodwork, because of the action of the alkali
on paint and wood; they roughen the surface and discolor the paint.
Waters vary so in composition, that a material suitable for softening
one may not prove to be the best for softening another. The special kind
must be determined largely by trial, and it should be the aim to use as
little as possible. When carbolic acid, formaline, bleaching powder, and
caustic soda are used, the hands should be protected and the clothes
should be well rinsed.
[Illustration: FIG. 64.--TYPHOID BACILLI.]
278. Economic Value of a Pure Water Supply.--From a financial point of
view, the money spent in securing pure water is one of the best
investments a community can make. Statisticians estimate the death of an
adult results in a loss to the state of from $1000 to $5000; and to the
losses sustained by death must be added those incurred by sickness and
by lessened quality and quantity of work through impaired
vitality,--all caused by using poor drinking water. Wherever plants have
been installed for improving the sanitary condition of the water supply,
the death rate has been lowered and the returns to the community have
been far greater than the cost of the plant. Impure water is the most
expensive food that can be consumed.
CHAPTER XX
FOOD AS AFFECTED BY HOUSEHOLD SANITATION AND STORAGE
279. Injurious Compounds in Foods.--An ordinary chemical analysis of a
food determines only the nutrients, as protein, carbohydrates, and fats;
and unless there is reason to believe the food contains injurious
substances no special tests for these are made. There are a number of
poisonous compounds that foods may contain, and many of them can but
imperfectly be determined by chemical analysis. Numerous organic
compounds are produced in foods as the result of the workings of
microörganisms; some of these are poisonous, while others impart only
special characteristics, as taste and odor. The poisonous bacteria
finding their way into food produce organic compounds of a toxic
character; and hence it is that the sanitary condition of a food, as
influenced by preparation and storage, is often of more vital importance
than the nutrient content.[95]
[Illustration: FIG. 65.--TUBERCULOSIS BACILLI. (After CONN.)
Often present in dust particles and contaminated foods.]
280. Sources of Contamination of Food.--As a rule, too little
attention is given to the sanitary handling and preparation of foods.
They are often exposed to impure air and to the dust and filth from
unclean streets and surroundings, and as a result they become inoculated
with bacteria, which are often the disease-producing kind. Gelatine
plates exposed by bacteriologists under the same conditions as foods
develop large numbers of injurious microörganisms. In order to avoid
contamination in the handling of food, there must be: (1) protection
from impure air and dust; (2) storage in clean, sanitary, and ventilated
storerooms and warehouses; (3) storage of perishable foods at a low
temperature so as to retard fermentation changes; and (4) workmen free
from contagious diseases in all occupations pertaining to the
preparation of foods. Ordinarily, foods should not be stored in the
paper wrappers in which they are purchased, as unclean paper is often a
source of contamination.
281. Sanitary Inspection of Food.--During recent years some state and
city boards of health have introduced sanitary inspection of foods, with
a view of preventing contamination during manufacture and
transportation, and this has done much to improve the quality and
wholesomeness. Putrid meats, fish, and vegetables are not allowed to be
sold, and foods are required to be handled and stored in a sanitary way.
Next to a pure water supply, there is no factor that so greatly
influences for good the health of a community as the sanitary condition
of the food. While the cooking of foods destroys many organisms, it
often fails to render innocuous the poisons which they produce, and
furthermore the unsound foods when cooked are not entirely wholesome,
and they have poor keeping qualities.
Often meats, vegetables, and other foods eaten uncooked, as well as the
numerous cooked foods, are exposed in dirty market places, and
accumulate large amounts of filth, and are inoculated with disease germs
by flies. Protection of food from flies is a matter of vital importance,
as they are carriers of many diseases. In the case of typhoid fever,
next to impure drinking water flies are credited with being the greatest
distributors of the disease germs.[96]
[Illustration: FIG. 66.--DIPHTHERIA BACILLI. (After CONN.)
Often present in dust particles and in food unprotected from dust.]
282. Infection from Impure Air.--The dust particles of the air contain
decayed animal and vegetable matter in which bacteria are present; these
find their way into the food when it is not carefully protected, into
the water supply, and also into the lungs and other organs of the body.
When foods are protected from the mechanical impurities which gain
access through the air, and fermentation is delayed by storage at a low
temperature, digestion disorders are greatly lessened. From a sanitary
point of view, the air of food storerooms and of living rooms should be
of equally high purity. When foods are kept in unventilated living
rooms, they become contaminated with the impurities thrown off from the
lungs in respiration, which include not only carbon dioxid, but the more
objectionable toxic organic materials.
Vegetable foods need to be stored in well-ventilated places, as the
plant cells are still alive and carrying on life functions, as the
giving off of carbon dioxid, which is akin to animal respiration; in
fact, it is plant-cell respiration. Provision should be made for the
removal of the carbon dioxid and other products, as they contaminate the
air. When vegetable tissue ceases to produce carbon dioxid, death and
decay set in, accompanied by fermentation changes.
283. Storage of Food in Cellars.--Cellars are often in a very
unsanitary condition, damp, poorly lighted, unventilated, and the air
filled with floating particles from decaying vegetables. The walls and
shelves absorb the dust and germs from the foul air and are bacterially
contaminated, and whenever a sound food is stored in such a cellar, it
readily becomes inoculated with bacteria. There is a much closer
relationship existing between the atmosphere of the cellar and that of
the house than is generally realized. An unclean cellar means
contaminated air throughout the house. When careful attention is given
to the sanitary condition of the cellar, many of the more common
diseases are greatly reduced. Cases of rheumatism have often been traced
to a damp cellar. In some localities where the cellars are unusually
unsanitary, there is in the season of spring rains, when they are
especially damp and contain the maximum of decayed vegetation, a
prevalence of what might be called "cellaritis." The symptoms differ and
the trouble is variously attributed, but the real cause is the same,
although overlooked, for, unfortunately, doctors do not visit the
cellar.
Cellars should be frequently cleaned and disinfected, using for the
purpose some of the well-known disinfectants, as formaline, bleaching
powder, or a dilute solution of carbolic acid. It has been found in
large cities, when the spread of such diseases as yellow fever was
imminent, that a general and thorough cleaning up of streets and cellars
with the improved sanitary conditions resulting greatly lowered the
usual death rate.
[Illustration: Fig. 67.--DUNG FUNGUS. (After BUTTERS.)
Often present on surface of unclean vegetables.]
284. Sunlight, Pure Water, and Pure Air as Disinfectants.--The most
effectual and valuable disinfectants are sunlight, pure water, and pure
air. Many kinds of microörganisms, particularly those that are
disease-producing, are destroyed when exposed for a time to sunlight.
The chemical action of the sun's rays is destructive to the organic
material which makes up the composition of many of these organisms,
while higher forms of organic life are stirred into activity by it. The
disinfecting power of sunlight should be made use of to the fullest
extent, not only in the house, but plenty of sunlight should also be
planned for in constructing barns and other buildings where milk-and
meat-producing animals are kept. Pure water is also a disinfectant, but
when water becomes polluted it loses this power. Many disease-producing
organisms are rendered inactive when placed in pure water. Water
contains more dissolved oxygen than air, and apparently a portion of the
oxygen in water is in a more active condition than that in air. Pure
air, too, is a disinfectant; the ozone and hydrogen peroxide and oxides
of nitrogen, which are present in traces, exert a beneficial influence
in oxidizing organic matter. Fresh air and sunlight, acting jointly, are
nature's most effectual disinfectants. Sunshine, fresh air, and pure
water are a health-producing trinity. In discussing the importance of
pure air, water, and sunlight, Ellen H. Richards[97] says:
"The country dweller surrounds his house with evergreens or shade
trees, the city dweller is surrounded with high brick walls.
Blinds, shades, or thick draperies shut out still more, and prevent
the beneficial sunlight from acting its role of germ prevention and
germ destruction. Bright-colored carpets and pale-faced children
are the opposite results which follow. Sunlight, pure air, and pure
water are our common birthright which we often bargain away for
so-called comforts."
And Dr. Woods Hutchinson says of sunlight:
"It is a splendid and matchless servant in the promoting of
healthfulness of the house, for which no substitute has yet been
discovered. It is the foe alike of bacilli and the blues; the best
tonic ever yet invented for the liver and for the scalp, and for
everything between, the only real complexion restorer, and the
deadliest foe of dirt and disease."
[Illustration: FIG. 68.--DIRT AND MANURE EMBEDDED IN SURFACE OF CELERY.]
285. Utensils for Storage of Food.--In order that dishes and household
utensils may be kept in the best sanitary condition, they should be free
from seams, cracks, and crevices where dust and dirt particles can find
lodgment. From the seams of a milk pail that has not been well washed,
decaying milk solids can be removed with the aid of a pin or a
toothpick. This material acts as a "starter" or culture when pure, fresh
milk is placed in the pail, contaminating it and causing it to become
sour. Not only is this true of milk, but also of other foods. Wooden
utensils are not satisfactory for the handling, storage, or preparation
of foods, as it is difficult to keep wood in a sanitary condition.
Uncleanliness of dishes in which foods are placed is too often caused by
the use of foul dishcloths and failure to thoroughly wash and rinse the
dishes. It is always well to rinse dishes with scalding water, as colds
and skin diseases may be communicated from the edges of drinking
glasses, and from forks and spoons, and, unless the dish towels are kept
scrupulously clean, it is more sanitary to drain the dishes than to wipe
them.
286. Contamination from Unclean Dishcloths.--When the dishcloth is
foul, the fat absorbed by the fibers becomes rancid, the proteids
undergo putrefaction changes with formation of ill-smelling gases
containing nitrogen, the carbohydrates ferment and are particularly
attractive to flies, and all the various disease germs collected on the
surface of the dishcloth are, along with the rancid fat and other
putrifying materials, distributed over the surface of the dishes with
which the cloth comes in contact.
[Illustration: FIG. 69.--CONTAMINATION OF WELL WATER FROM SURFACE DRAINAGE.
(After Farmers' Bulletin, U. S. Dept. Agr.)]
287. Refrigeration.--At a low temperature the insoluble or unorganized
ferments become inactive, but the chemical ferments or enzymes are still
capable of carrying on fermentation. Thus it is that a food, when placed
in a refrigerator or in cold storage, continues to undergo chemical
change. An example of such enzymic action is the curing of beef and
cheese in cold storage. A small amount of ventilation is required when
foods are refrigerated, just sufficient to keep up a slight circulation
of air. It seems not to be generally understood that all fermentation
changes do not cease when food is placed in refrigerators, and this
often leads to neglect in their care. Cleanliness is equally as
essential, or more so, in the refrigeration of food as in its handling
in other ways. Too often the refrigerator is neglected, milk and other
food is spilt, filling the cracks, and slow decomposition sets in. A
well-cared-for refrigerator is an important factor in the preservation
of food, but when it is neglected, it becomes a source of contamination.
Unclean vegetables and food receptacles, impure ice and foul air, are
the most common forms of contamination. The chemical changes which
foods undergo during refrigeration are such as result in softening of
the tissues.
288. Soil.--The soil about dwellings and places where foods are stored
frequently becomes polluted with decaying animal and vegetable matter,
and in such soils disease-producing organisms readily find lodgment.
Poorly drained soils containing an excess of vegetable matter furnish a
medium in which the tapeworm and the germs of typhoid fever, lockjaw,
and various diseases affecting the digestive tract, may propagate. The
wind carries the dust particles from these contaminated places into
unprotected food, where they cause fermentation changes and the disease
germs multiply. In considering the sanitary condition of a locality, the
character of the soil is an important factor. Whenever there is reason
to suspect that a soil is unsanitary, it should be disinfected with lime
or formaldehyde. Soils about dwellings need care and frequent
disinfecting to keep them in a sanitary condition, equally as much as do
the rooms in the dwellings.[99] In the growing of garden vegetables,
frequently large quantities of fertilizers of unsanitary character are
used, and vegetables often retain mechanically on their surfaces
particles of these. To this dirt clinging to the vegetables have been
traced diseases, as typhoid fever and various digestion disorders.
289. Disposal of Kitchen Refuse.--Refuse, as vegetable parings, bones,
and meat scraps, unless they are used for food for animals or collected
as garbage, should preferably be burned; then there is no danger of
their furnishing propagating media for disease germs. Garbage cans
should be kept clean, and well covered to protect the contents from
flies. Where the refuse cannot be burned, it should be composted. For
this, a well-drained place should be selected, and the refuse should be
kept covered with earth to keep off the flies and absorb the odors that
arise from the fermenting material, and to prevent its being carried
away by the wind. Lime should be sprinkled about the compost heap, and
from time to time it should be drawn away and the place covered with
clean earth. It is very unsanitary to throw all of the kitchen refuse in
the same place year after year without resorting to any means for
keeping the soil in a sanitary condition. Although composting refuse is
not as sanitary as burning, it is far more sanitary than neglecting to
care for it at all, as is too frequently the case.
Ground polluted with kitchen refuse containing large amounts of fatty
material and soap becomes diseased, so that the natural fermentation
changes fail to take place, and the soil becomes "sewage sick" and gets
in such a condition that vegetation will not grow. Failure to properly
dispose of kitchen refuse is frequently the cause of the spread of germ
diseases, through the dust and flies that are attracted by the material
and carry the germs from the refuse pile to food.
[Illustration: FIG. 70.--PLUMBING OF SINK.
1, 1, house side of trap, filled with water; 2, vent pipe; 3, drain pipe
connecting with sewer.]
Where there is no drainage system, disposal of the liquid refuse is a
serious problem. Drain basins and cesspools are often resorted to, and
these may become additional sources of contamination. As stated in the
chapter on well water, direct communication is frequently established
between such places and shallow wells. Where the only place for the
disposal of waste water is the surface of the ground, it should be
thrown some distance from the house and where it will drain from and not
toward the well. The land should be well drained and open to the
sunlight. Coarse sand and lime should be sprinkled over it frequently,
and occasionally the soil should be removed and replaced with fresh.
Sunlight, aëration, and disinfection of the soil and good drainage are
necessary, in order to keep in a sanitary condition the place where the
dish water is thrown.
Poor plumbing is often the cause of contaminated food. The gases which
escape from unclean traps may carry with them solid particles of organic
matter in various stages of decay. The "house side" of traps always
ventilates into the rooms, and hence it is important that they be kept
scrupulously clean. Where the drip pipe from the refrigerator drains
directly into the sewerage system, there is always danger. Special
attention should be given to the care of plumbing near places where
foods are stored. Frequently there are leaky joints due to settling of
the dwellings or to extreme changes in temperature, and the plumbing
should be occasionally inspected by one familiar with the subject.[100]
290. General Considerations.--In order to keep food in the most
wholesome condition, special care should be taken that all of its
surroundings are sanitary. The air, the dishes in which the food is
placed, the refrigerator, cellar or closet where stored, and the other
food with which it comes in contact, all influence the wholesomeness or
cause contamination. A food may contain sufficient nutrients to give it
high value, and yet, on account of products formed during fermentation,
be poisonous. Foods are particularly susceptible to putrefaction
changes, and chemicals and preservatives added as preventives, with a
view of retarding these changes, are objectionable, besides failing to
prevent all fermentation from taking place. Intelligent thought should
be exercised in the care of food, for the health of the consumer is
largely dependent upon the purity and wholesomeness of the food supply.
[Illustration: FIG. 71.--A PETRI DISH, SHOWING COLONIES OF
BACTERIA PRODUCED BY ALLOWING A HOUSE FLY TO CRAWL OVER SURFACE.
(From Minnesota Experiment Station Bulletin No. 93.)]
CHAPTER XXI
LABORATORY PRACTICE
Object of Laboratory Practice, Laboratory Note-book, and Suggestions
for Laboratory Practice.--The aim of the laboratory practice is to give
the students an idea of the composition, uses, and values of food
materials, and the part which chemistry takes in sanitation and
household affairs; also to enable them by simple tests to detect some of
the more common adulterants in foods.
Before performing an experiment, the student is advised to review those
topics presented in the text which have a bearing upon the experiment,
so that a clear conception may be gained of the relationship between the
laboratory work and that of the class room. The student should endeavor
to cultivate the power of observation and to grasp the principle
involved in the work, rather than do it in a merely mechanical and
perfunctory way. Neatness is one of the essentials for success in
laboratory practice, and too much emphasis cannot be laid upon this
requisite to good work. The student should learn to use his time in the
laboratory profitably and economically. He should obtain a clear idea of
what he is to do, and then do it to the best of his ability. If the
experiment is not a success, repeat it. While the work is in progress it
should be given undivided attention. Care should be exercised to prevent
anything getting into the sinks that will clog the plumbing; soil,
matches, broken glass, and paper should be deposited in the waste jars.
[Illustration: FIG. 72.--APPARATUS USED IN LABORATORY WORK.
See page 301 for names.]
A careful record of the experiments should be kept by each student in a
suitable note-book. It is suggested that those students desiring more
time in writing out the experiments than the laboratory period affords,
take notes as they make the various tests, and then amplify and
rearrange them in the evening study time. The final writing up of the
notes should, however, be done before the next laboratory period.
Careful attention should be given to the spelling, language, and
punctuation, and the note-book should represent the student's individual
work. He who attempts to cheat by copying the results of others, only
cheats himself. In recording the results of an experiment, the student
should state briefly and clearly the following:
1. Number and title of experiment.
2. How the experiment is performed.
3. What was observed.
4. What the experiment proves.
[Illustration: FIG. 73.--BALANCE AND WEIGHTS.]
LIST OF APPARATUS USED IN EXPERIMENTS
1 Crucible Tongs
2 Evaporating Dishes
1 Casserole
6 Beakers
12 Test Tubes
1 Wooden Stand
1 Test Tube Stand
1 Sand Bath
2 Funnels
1 Tripod
1 Stoddart Test Tube Clamp
1 Test Tube Brush
1 Burner and Tubing
2 Stirring Rods
6 Watch Glasses
2 Erlenmeyer Flasks
1 Package Filter Paper
1 Box Matches
1 Wire Gauze
2 Burettes
1 Porcelain Crucible
1 Aluminum Dish
Directions for Weighing.--Place the dish or material to be weighed in
the left-hand pan of the balance. With the forceps lay a weight from the
weight box on the right-hand pan. Do not touch the weights with the
hands. If the weight selected is too heavy, replace it with a lighter
weight. Add weights until the pans are counterpoised; this will be
indicated by the needle swinging nearly as many divisions on one side of
the scale as on the other. The brass weights are the gram weights. The
other weights are fractions of a gm. The 500, 200, 100 mg. (milligram)
weights are recorded as 0.5, 0.2, and 0.1 gm. The 50, 20, and 10 mg.
weights as 0.05, 0.02, and 0.01 gm. If the 10, and 2 gm., and the 200,
the 100, and the 50 mg. weights are used, the resulting weight is 12.35
gms. No moist substances should ever come in contact with the scale
pans. The weights and forceps should always be replaced in the weight
box. Too much care and neatness cannot be exercised in weighing.
[Illustration: FIG. 74.]
[Illustration: FIG. 75.--Pouring Reagent from Bottle.]
Directions for Measuring.--Reagents are measured in graduated
cylinders (see Fig. 74). When the directions call for the addition of 5
or 10 cc. of a reagent, unless so directed it is not absolutely
necessary to measure the reagent in a measuring cylinder. A large test
tube holds about 30 cc. of water. Measure out 5 cc. of water and
transfer it to a large test tube. Note its volume. Add approximately 5
cc. of water directly to the test tube. Measure it. Repeat this
operation until you can judge with a fair degree of accuracy the part of
a test tube filled by 5 cc. In the experiments where a burette is used
for measuring reagents, the burette is first filled with the reagent by
means of a funnel. The tip of the burette is allowed to fill before the
readings are made, which are from the lowest point or meniscus. When
reagents are removed from bottles, the stopper should be held between
the first and second fingers of the right hand (see Fig. 75). Hold the
test tube or receptacle that is to receive the reagent in the left hand.
Pour the liquid slowly until the desired amount is secured. Before
inserting the stopper, touch it to the neck of the bottle to catch the
few drops on the edge, thus preventing their streaking down the sides of
the bottle on to the shelf. Replace the bottle in its proper place.
Every precaution should be taken to prevent contamination of reagents.
[Illustration: FIG. 76.--MICROSCOPE AND ACCESSORIES.
1, eye-piece or ocular; 2, objective; 3, stage; 4, cover glass; 5,
slide; 6, mirror.]
Use of the Microscope.--Special directions in the use of the
microscope will be given by the instructor. The object or material to be
examined is placed on a microscopical slide. Care should be exercised to
secure a representative sample, and to properly distribute the substance
on the slide. If a pulverized material is to be examined, use but little
and spread it in as thin a layer as possible. If a liquid, one or two
drops placed on the slide will suffice. The material on the slide is
covered with a cover glass, before it is placed on the stage of the
microscope. In focusing, do not allow the object glass of the microscope
to come in contact with the cover glass. Focus upward, not downward.
Special care should be exercised in focusing and in handling the
eye-piece and objective. A camel's-hair brush, clean dry chamois skin,
or clean silk only should be used in polishing the lenses. Always put
the microscope back in its case after using.
Experiment No. 1
Water in Flour
Carefully weigh a porcelain or aluminum dish. (Porcelain must be used if
the ash is to be determined on the same sample.) Place in it about 2 gm.
of flour; record the weight; then place the dish in the water oven for
at least 6 hours. After drying, weigh again, and from the loss of weight
calculate the per cent of water in the flour. (Weight of flour and dish
before drying minus weight of flour and dish after drying equals weight
of water lost. Weight of water divided by weight of flour taken,
multiplied by 100, equals the per cent of water in the flour.)
How does the amount of water you obtained compare with the amount given
in the tables of analysis?
Experiment No. 2
Water in Butter
Carefully weigh a clean, dry aluminum dish, place in it about 2 gms. of
butter, and weigh again. Record the weights. Place the dish containing
butter in the water oven for 5 or 6 hours and then weigh. The loss in
weight represents the water in the butter. Calculate the per cent of
water. Care must be taken to get a representative sample of the butter
to be tested; preferably small amounts should be taken with the butter
trier from various parts of the package.
Experiment No. 3
Ash in Flour
Place the porcelain dish containing flour from the preceding experiment
in a muffle furnace and let it remain until the organic matter is
completely volatilized. Cool, weigh, and determine the per cent of ash.
The flour should be burned at the lowest temperature necessary for
complete combustion.
Experiment No. 4
Nitric Acid Test for Nitrogenous Organic Matter
To 3 cc. of egg albumin in a test tube add 2 cc. of HNO_{3} (conc.) and
heat. When cool add NH_{4}OH. The nitric acid chemically reacts upon the
albumin, forming yellow xanthoprotein. What change occurs in the
appearance of the egg albumin when the HNO_{3} is added? Is this a
physical or chemical change? What is the name of the compound formed?
What change occurs on adding NH_{4}OH?
Experiment No. 5
Acidity of Lemons
With a pipette measure into a small beaker 2 cc. of lemon juice. Add 25
cc. of water and a few drops of phenolphthalein indicator. From the
burette run in N/10 KOH solution until a faint pink tinge remains
permanently. Note the number of cubic centimeters of KOH solution
required to neutralize the citric acid in the lemon juice. Calculate the
per cent of citric acid.
(1 cc. of N/10 KOH solution equals 0.00642 gm. citric acid. 1 cc. of
H_{2}O weighs 1 gm. Because of sugar and other matter in solution 1 cc.
of lemon juice weighs approximately 1.03 gm.)
1. What is the characteristic acid of lemons? 2. What is the salt formed
when the lemon juice is neutralized by the KOH solution? 3. Describe
briefly the process for determining the acidity of lemon juice. 4. What
per cent of acidity did you obtain? 5. How does this compare with the
acidity of vinegar?
Experiment No. 6
Influence of Heat on Potato Starch Grains
With the point of a knife scrape slightly the surface of a raw potato
and place a drop of the starchy juice upon the microscopical slide.
Cover with cover glass and examine under the microscope.
In the evaporating dish cook a small piece of potato, then place a very
small portion upon the slide, and examine with the microscope.
Make drawings of the starch grains in raw and in cooked potatoes.
Experiment No. 7
Influence of Yeast on Starch Grains
Moisten a small portion of the dough prepared with yeast and with the
stirring rod place a drop of the starchy water upon the slide. Cover
with cover glass and examine under the microscope.
Repeat, examining a drop of starchy water washed from flour.
Make drawing of wheat starch grain in flour and in dough prepared with
yeast.
Experiment No. 8
Mechanical Composition of Potatoes
Wash one potato. Weigh, then peel, making the peeling as thin as
possible. Weigh the peeled potato and weigh the peeling or refuse.
Calculate the per cent of potato that is edible and the per cent that is
refuse.
Experiment No. 9
Pectose from Apples
Reduce a small peeled apple to a pulp. Squeeze the pulp through a clean
cloth into a beaker. Add 10 cc. H_{2}O and heat on a sand bath to
coagulate the albumin. Filter, adding a little hot water if necessary.
To the filtrate add 5 cc. alcohol. The precipitate is the pectose
material.
1. Is the pectose from the apple soluble? 2. Is it coagulated by heat?
3. Is it soluble in alcohol?
Experiment No. 10
Lemon Extract
To 5 cc. of the extract in a test tube add an equal volume of water. A
cloudy appearance indicates the presence of lemon oil. If the solution
remains clear after adding the water, the extract does not contain lemon
oil.
Why does the extract containing lemon oil become cloudy on adding water?
Experiment No. 11
Vanilla Extract
Pour into a test tube 5 cc. of the extract to be tested. Evaporate to
one third. Then add sufficient water to restore the original volume. If
a brown, flocculent precipitate is formed, the sample contains pure
vanilla extract. Resin is present in vanilla beans and is extracted in
the essence. The resin is readily soluble in 50 per cent alcohol. If
the alcohol is removed from the extract, the excess of resin is
precipitated, or if free from alkali, it may be precipitated by diluting
the original solution with twice its volume of water. Test the two
samples and compare.
(Adapted from Leach, "Food Inspection and Analysis.")
1. Describe the appearance of each sample after evaporating and adding
water. 2. Which sample contains pure vanilla extract? 3. State the
principle underlying this test.
Experiment No. 12
Testing Olive Oil for Cotton Seed Oil
Pour into a test tube 5 cc. of the oil to be tested and 5 cc. of
Halphen's Reagent. Mix thoroughly. Plug the test tube loosely with
cotton, and heat in a bath of boiling saturated brine for 15 minutes. If
cotton seed oil is present, a deep red or orange color is produced. Test
two samples and compare.
Halphen's Reagent.--Mix equal volumes of amyl alcohol and carbon
disulphid containing about one per cent of sulphur in solution.
(Adapted from Leach, "Food Inspection and Analysis.")
Experiment No. 13
Testing for Coal Tar Dyes
Dilute 20 to 30 cc. of the material to 100 cc.; boil for 10 minutes with
10 cc. of a 10 per cent solution of potassium bisulphate and a piece of
white woolen cloth which has previously been boiled in a 0.1 per cent
solution of NaOH and thoroughly washed in water. Remove the cloth from
the solution, wash in boiling water, and dry between pieces of filter
paper. A bright red indicates coal tar dye. If the coloring matter is
entirely from fruit, the woolen cloth will be either uncolored or will
have a faint pink or brown color which is changed to green or yellow by
ammonia and is not restored by washing. This is the Arata test.
(Adapted, Winston, Conn. Experiment Station Report.)
1. Describe Arata's wool test for coal tar dyes. 2. What is the
appearance of the woolen cloth when the coloring matter is entirely from
fruit? 3. What effect has NH_{4}OH upon the color? 4. Why is NaOH used?
5. Why may not cotton cloth be used instead of woolen? 6. What can you
say of the use of coal tar dyes in foods?
Experiment No. 14
Determining the Per Cent of Skin in Beans
Place in an evaporating dish 10 gm. of beans, 50 cc. of water, and 1/2
gm. of baking soda. Boil 10 minutes or until the skins are loosened,
then drain off the water. Add cold water and rub the beans together till
the skins slip off. Collect the skins, place on a watch glass and dry in
the water oven for 1/2 hour. Weigh the dried skins and calculate the per
cent of "skin."
1. What does the soda do? 2. What effect would hard limewater have upon
the skins? 3. How does removal of skins affect food value of beans and
digestibility?
Experiment No. 15
Extraction of Fat from Peanuts
Shell three or four peanuts and with the mortar and pestle break them
into small pieces. Place in a test tube and pour over them about 10 cc.
of ether. Cork the test tube and allow it to stand 30 minutes, shaking
occasionally. Filter on to a watch glass and let stand until the ether
evaporates, and then observe the fat.
1. What is the appearance of the peanut fat? 2. What is the solvent of
the fat? 3. What becomes of the ether? 4. Why should the peanuts be
broken into small pieces?
Experiment No. 16
Microscopic Examination of Milk
Place a drop of milk on a microscopical slide and cover with cover
glass. Examine the milk to detect impurities, as dust, hair, refuse,
etc. Make drawings of any foreign matter present.
Experiment No. 17
Formaldehyde in Cream or Milk
To 10 cc. of milk in a casserole add 10 cc. of the acid reagent. Heat
slowly over the flame nearly to boiling, holding the casserole in the
hand and giving it a slight rotary movement while heating. The presence
of formaldehyde is indicated by a violet coloration varying in depth
with the amount present. In the absence of formaldehyde the solution
slowly turns brown.
Acid Reagent.--Commercial hydrochloric acid (sp. gr. 1.2) containing 2
cc. per liter of 10 per cent ferric chlorid.
(Adapted from Leach, "Food Inspection and Analysis.")
1. How may the presence of formaldehyde in milk be detected? 2. Why in
this test is it necessary to use acid containing ferric chlorid? 3.
Describe the appearance of the two samples of milk after adding the acid
reagent and heating. 4. Which sample showed the presence of
formaldehyde?
Experiment No. 18
Gelatine in Cream or Milk
To 20 cc. of milk or cream in a beaker add 20 cc. of acid mercuric
nitrate and about 40 cc. of H_{2}O. Let stand for a few minutes and
filter. Filtrate will be cloudy if gelatine is present.
Add 1/2 cc. of a dilute solution of picric acid--a heavy yellow
precipitate indicates gelatine.
Acid Mercuric Nitrate.--1 part by weight of Hg, 2 parts HNO_{3} (sp.
gr. 1.42). Dilute 25 times with water.
Experiment No. 19
Testing for Oleomargarine
Apply the following tests to two samples of the material:
Boiling or Spoon Test.--Melt the sample to be tested--a piece about
the size of a chestnut--in a large spoon, hastening the process by
stirring with a splinter. Then, increasing the heat, bring to as brisk a
boil as possible and stir thoroughly, not neglecting the outer edges.
Oleomargarine and renovated butter boil noisily, sputtering like a
mixture of grease and water, and produce no foam, or but very little.
Genuine butter boils with less noise and produces an abundance of foam.
Waterhouse Test.--Into a small beaker pour 50 cc. of sweet milk. Heat
nearly to boiling and add from 5 to 10 gms. of butter or oleomargarine.
Stir with a glass rod until fat is melted. Then place the beaker in cold
water and stir the milk until the temperature falls sufficiently for the
fat to congeal. At this point the fat, if oleomargarine, can easily be
collected into one lump by means of the rod; while if butter, it will
granulate and cannot be collected.
(From Farmers' Bul. 131, U. S. Dept. of Agriculture.)
1. Name two simple tests for distinguishing butter and oleomargarine. 2.
Describe these tests. 3. Why do butter and oleomargarine respond
differently to these tests? 4. Are these tests based upon chemical or
physical properties of the fats?
Experiment No. 20
Testing for Watering or Skimming of Milk
_a._ Fat Content of Milk by Means of Babcock Test.--Measure with
pipette into test bottle 17.6 cc. of milk. Sample should be carefully
taken and well mixed. Measure with cylinder 17.5 cc. commercial
H_{2}SO_{4} and add to milk in test bottle. (See Fig. 25.) Mix acid and
milk by rotating the bottle. Then place test bottles in centrifugal
machine and whirl 5 minutes. Add sufficient hot water to test bottles to
bring contents up to about the 8th mark on stem. Then whirl bottles 2
minutes longer and read fat. Read from extreme lowest to highest point.
Each large division as 1 to 2 represents a whole per cent, each small
division 0.2 of a per cent.
_b._ Determining Specific Gravity by Means of Lactometer.--Pour 150
cc. of milk into 200 cc. cylinder. Place lactometer in milk and note
depth to which it sinks as indicated on stem. Note also temperature of
milk. For each 10° above 60° F. add 1 to the lactometer number, in order
to make the necessary correction for temperature. For example, if milk
has sp. gr. of 1.032 at temperature of 70°, it will be equivalent to sp.
gr. of 1.033 at 60°. Ordinarily milk has a sp. gr. of 1.029 to 1.034. If
milk has sp. gr. less than 1.029, or contains less than 3 per cent fat,
it may be considered watered milk. If the milk has a high sp. gr. (above
1.035) and a low content of fat, some of the fat has been removed.
(For extended direction for milk testing see Snyder's "Dairy Chemistry.")
Experiment No. 21
Boric Acid in Meat
Cut into very small pieces 5 gms, of meat, removing all the fat
possible. Place in an evaporating dish with 20 to 25 cc. of water to
which a few drops of HCl have been added and warm slightly. Dip a piece
of turmeric paper in the meat extract and dry. A rose-red color of the
turmeric paper after drying (turned olive by a weak ammonia solution) is
indicative of boric acid.
1. How may meat be tested for boric acid? 2. Why is HCl added to the
water? 3. Why is the water containing the meat warmed slightly? 4. What
is the appearance of the turmeric paper after being dipped in the meat
extract and dried? 5. What change takes place when it is moistened with
ammonia, and why?
Experiment No. 22
Microscopic Examination of Cereal Starch Grains
Make a microscopic examination and drawings of wheat, corn, rice, and
oat starch grains, comparing them with the drawings of the different
starch grains on the chart. If the material is coarse, pulverize in a
mortar and filter through cloth. Place a drop or two of the starchy
water on the slide, cover with a cover glass, and examine.
Experiment No. 23
Identification of Commercial Cereals
Examine under the microscope two samples of cereal breakfast foods, and
by comparison with the wheat, corn, and oat starch grains previously
examined tell of what grains the breakfast foods are made and their
approximate food value.
Experiment No. 24
Granulation and Color of Flour
Arrange on glass plate, in order of color, samples of all the different
grades of flour. Note the differences in color. How do these differences
correspond with the grades of the flour? Examine the flour with a
microscope, noting any coarse or dark-colored particles of bran or dust.
Rub some of the flour between the thumb and forefinger. Note if any
granular particles can be detected.
Experiment No. 25
Capacity of Flour to absorb Water
Weigh out 15 gms. of soft wheat flour into an evaporating dish; then add
from burette a measured quantity of water sufficient to make a stiff
dough. Note the amount of water required for this purpose. Repeat the
operation, using hard wheat flour.
1. How may the absorptive power of a flour be determined? 2. To what is
it due? 3. Why do some flours absorb more water than others?
Experiment No. 26
Acidity of Flour
Weigh into a flask 20 gms. of flour and add 200 cc. distilled water.
Shake vigorously. After letting stand 30 minutes, filter and then
titrate 50 cc. of the filtrate against standard KOH solution, using
phenolphthalein as indicator, 1 cc. of the alkali equals 0.009 gms.
lactic acid. Calculate the per cent of acid present.
1. How may the acidity of a flour be determined? 2. The acidity is
expressed in percentage amounts of what acid? 3. What per cent of
acidity is found in normal flours? 4. What does a high acidity of a
flour indicate?
Experiment No. 27
Moist and Dry Gluten
Weigh 30 gms. of flour into a porcelain dish. Make the flour into a
stiff dough. After 30 minutes obtain the gluten by washing, being
careful to remove all the starch and prevent any losses. Squeeze the
water from the gluten as thoroughly as possible. Weigh the moist gluten
and calculate the per cent. Dry the gluten in the water oven and
calculate the per cent of dry gluten.
Experiment No. 28
Gliadin from Flour
Place in a flask 10 gms. of flour, 30 cc. of alcohol, and 20 cc. of
water. Cork the flask and shake, and after a few minutes shake again.
Allow the alcohol to act on the flour for an hour, or until the next
day. Then filter off the alcohol solution and evaporate the filtrate to
dryness over the water bath. Examine the residue; to a portion add a
little water; burn a small portion and observe odor.
1. Describe the appearance of the gliadin. 2. What was the result when
water was added? 3. When burned, what was the odor of the gliadin, and
what does this indicate? 4. What is gliadin?
Experiment No. 29
Bread-making Test
Make a "sponge" by mixing together:
12 gm. sugar,
12 gm. yeast (compressed),
4 gm. salt,
175 cc. water (temp. 32° C.).
Let stand 1/2 hour at a temperature of 30° C. In a large bowl, mix with
a knife or spatula 7.7 gms. of lard with 248.6 gms. of flour. Then add
160 cc. of the "sponge," or as much as is needed to make a good stiff
dough, and mix thoroughly, using the spatula. With some flours as small
a quantity as 150 cc. of sponge may be used. If more moisture is
necessary, add H_{2}O. Keep at temperature of 30° C. Allow the dough to
stand 50 minutes to first pulling, 40 minutes to second pulling, and 30
to 50 minutes to the pan. Let it rise to top of pan and then bake for
1/2 hour in an oven at a temperature of 180° C. One loaf of bread is
made of patent flour of known quality as a standard for comparison, and
other loaves of the flours to be tested. Compare the loaves as to size
(cubic contents), color, porosity, odor, taste, nature of crust, and
form of loaf.
Experiment No. 30
Microscopic Examination of Yeast
On a watch glass mix thoroughly a very small piece of yeast with about 5
cc. of water and then with the stirring rod place a drop of this
solution on the microscopical slide, adding a drop of very dilute methyl
violet solution. Cover with the cover glass and examine under the
microscope. The living active cells appear colorless while the decayed
and lifeless ones are stained. Yeast cells are circular or oval in
shape. (See Fig. 46.)
(Adapted from Leach, "Food Inspection and Analysis.")
Experiment No. 31
Testing Baking Powders for Alum
Place about 2 gms. of flour in a dish with 1/2 gm. baking powder. Add
enough water to make a dough and then 2 or 3 drops of tincture of
logwood and 2 or 3 drops of ammonium carbonate solution. Mix well and
observe; a blue color indicates alum. Try the same test, using flour
only for comparison.
1. How do you test a baking powder for alum? 2. What difference in color
did you observe in the test with the baking powder containing alum and
in that with the flour only? 3. Why is the (NH_{4})_{2}CO_{3} solution
used?
Experiment No. 32
Testing Baking Powders for Phosphoric Acid
Dissolve 1/2 gm. of baking powder in 5 cc. of H_{2}O and 3 cc. HNO_{3}.
Filter and add 3 cc. ammonium molybdate. Heat gently. A yellow
precipitate indicates phosphoric acid.
1. How do you test a baking powder for phosphoric acid? 2. What is the
yellow precipitate obtained in this test?
Experiment No. 33
Testing Baking Powders for Ammonia
Dissolve 1/2 gm. of material in 10 cc. water; filter off any insoluble
residue and to the filtrate add 2 or 3 cc. NaOH and apply heat. Test the
gas given off with moistened turmeric paper. If NH_{3} is present, the
paper will be colored brown. Do not allow the paper to come in contact
with the liquid or sides of the test tube. (Perform the tests on two
samples of baking powder.)
1. How do you test a baking powder for ammonia? 2. Why do you add NaOH?
3. Why must you be careful not to let the turmeric paper touch the sides
of the test tube or the liquid?
Experiment No. 34
Vinegar Solids
Into a weighed aluminum or porcelain dish pour 10 cc. of vinegar. Weigh
and then evaporate over boiling water. To drive off the last traces of
moisture dry in the water oven for an hour. Cool and weigh. Calculate
the per cent of solids. Observe the appearance of the solids. Test both
samples and compare.
1. How may the per cent of solids in vinegar be determined? 2. Describe
the appearance of the solids from the good and from the poor sample of
vinegar. 3. What is the legal standard for vinegar solids in your state?
Experiment No. 35
Specific Gravity of Vinegar
Pour 170 cc. vinegar into 200 cc. cylinder. Place a hydrometer for heavy
liquids (sp. gr. 1 to 1.1) in the cylinder. Note the depth to which it
sinks and the point registered on the scale on the stem. Note
temperature of vinegar. Record specific gravity of vinegar.
1. What effect would addition of water to vinegar have upon its specific
gravity? 2. What effect would addition of such material as sugar have
upon specific gravity? 3. Why should the specific gravity of vinegar be
fairly constant? 4. What would be the weight of 1000 cc. of vinegar
calculated from the specific gravity?
Experiment No. 36
Acidity of Vinegar
Into a small beaker pour 6 cc. of vinegar and 10 cc. of water and a few
drops of phenolphthalein indicator. Run in standard KOH solution from a
burette until a faint pink tinge remains permanently. Note the number of
cubic centimeters of KOH solution required to neutralize the acid.
Divide this number by 10, which will give approximately the per cent of
acetic acid.
1. How may the per cent of acidity of vinegar be determined? 2. Why was
phenolphthalein used? 3. Why was KOH used? 4. What acids does vinegar
contain? 5. What is the legal requirement in this state for acetic acid
in vinegar? 6. How did the acidity you obtained compare with this legal
requirement?
Experiment No. 37
Deportment of Vinegar with Reagents
To 10 cc. of vinegar in a test tube add 8 or 10 drops of lead
sub-acetate and shake. Observe the precipitate. Lead sub-acetate
precipitates mainly the malic acid which is always present in cider
vinegar.
1. How may the presence of malic acid in a vinegar be detected? 2.
Describe the precipitate. 3. What does malic acid in a vinegar indicate?
Experiment No. 38
Testing Mustard for Turmeric
Place 1 gm. of ground mustard on a small watch glass and moisten
slightly with water. Add 2 or 3 drops of NH_{4}OH, stirring well with a
glass rod. A brown color indicates turmeric present in considerable
quantity.
Test a sample of good mustard and one adulterated with turmeric and
compare the results.
Experiment No. 39
Examination of Tea Leaves
Soak a small amount of tea and unroll 8 or 10 of the leaves. Make a
drawing of a tea leaf. Observe the proportion of stems in each of three
samples of tea; also the relative proportion of large and small leaves.
Observe if the leaves are even as to size and of a uniform color.
Experiment No. 40
Action of Iron Compounds upon Tannic Acid
Make an infusion of tea by placing 3 gms. of tea in 100 cc. of hot water
and stirring well. Filter off some of the infusion and test 5 cc. with
ferrous sulphate solution made by dissolving 1 gm. FeSO_{4} in 10 cc.
H_{2}O and filtering. Note the result.
1. What change in color did you observe when the ferrous sulphate
solution was added to the tea infusion? 2. What effect would waters
containing iron have upon the tea infusion?
Experiment No. 41
Identification of Coffee Berries
Examine Rio, Java, and Mocha coffee berries. Describe each. Note the
characteristics of each kind of coffee berry.
Experiment No. 42
Detecting Chicory in Coffee
Fill a beaker with water and place about a teaspoonful of ground coffee
on the surface. If much of the ground material sinks and it imparts a
dark brown color to the lower portion of the liquid, it is an indication
of the presence of chicory. Pure coffee floats on water. Chicory has a
higher specific gravity than coffee.
1. How may the presence of chicory in ground coffee be detected? 2. Why
does coffee float on the water while chicory sinks? 3. What effect does
chicory have upon the color of water?
Experiment No. 43
Testing Hard and Soft Waters
Partially fill a large cylinder with very hard water. This may be
prepared by dissolving 0.1 to 0.2 gm. calcium chloride in 500 cc. of
ordinary water. Add to this a measured quantity of soap solution. Mix
well and notice how many cubic centimeters of soap solution must be used
before a permanent lather is formed, also notice the precipitate of
"lime soap." Repeat this experiment, using either rain or distilled
water, and compare the cubic centimeters of soap solution used with that
in former test. Repeat the test, using tap water.
Soap Solution.--Scrape 10 gms. of castile soap into fine shavings and
dissolve in a liter of alcohol, dilute with 1/3 water. Filter if not
clear and keep in a tightly stoppered bottle.
1. Why is more soap required to form a lather with hard water than with
soft water? 2. What is meant by "lime soap"? Describe its appearance. 3.
How may hard waters be softened for household purposes?
Experiment No. 44
Solvent Action of Water on Lead
Put 1 gm. of clean bright lead shavings into a test tube containing 10
cc. of distilled water. After 24 hours decant the clear liquid into a
second test tube, acidify slightly with HCL, and add a little hydrogen
sulphid water. A black or brownish coloration indicates lead in
solution.
(Adapted from Caldwell and Breneman, "Introductory Chemical Practice.")
Under what conditions may lead pipes be objectionable?
Experiment No. 45
Suspended Matter in Water
Place a drop of water on the microscopical slide, cover with cover
glass, and examine with the microscope. Note the occurrence and
appearance of any suspended matter in the water.
Experiment No. 46
Organic Matter in Water
Pour into the evaporating dish 100 cc. H_{2}O and evaporate to dryness
over the sand bath. Ignite the solids. If the solids blacken when
ignited, the water contains organic matter.
Experiment No. 47
Deposition of Lime by Boiling Water
Boil for a few minutes about 200 cc. of water in a flask. After the
water is cool, note any sediment of lime or turbidity of the water due
to expelling the carbon dioxid.
1. What is meant by a "hard" water? 2. What do the terms "temporary" and
"permanent" hardness of water mean? 3. What acts as a solvent of the
lime in water? 4. Why does boiling cause the lime to be deposited?
Experiment No. 48
Qualitative Tests for Minerals in Water
Test for Chlorids.--To 10 cc. of H_{2}O add a few drops of HNO_{3} and
2 cc. of AgNO_{3}. A white precipitate indicates the presence of
chlorids, usually in the form of sodium chlorid.
Test for Sulphates.--To 10 cc. of water add 2 cc. of dilute HCl and 2
cc. of BaCl_{2}. A cloudiness or the formation of a white precipitate
indicates the presence of sulphates.
Test for Iron.--If a brown sediment is formed in water exposed to the
air for some time, it is probably iron hydroxid. To 10 cc. of the water
add a few drops of HNO_{3}, heat, and then add 1/2 cc. of NH_{4}CNS. A
red color indicates the presence of iron.
Test for CaO and MgO.--To 10 cc. of H_{2}O add 5 cc. NH_{4}OH. If a
precipitate forms, filter it off, and to the filtrate add 3 cc. NH_{4}Cl
and 5 cc. (NH_{4})_{2}C_{2}O_{4}. The precipitate is CaC{2}O_{4}, and
the filtrate contains the magnesia. Filter and add 5 cc. Na_{3}PO_{4} to
precipitate MgNH_{4}PO_{4}.
1. How would you test a water to detect the presence of organic matter?
2. Name some mineral impurities often found in water. 3. Describe the
test for chlorids; for sulphates; for iron; for lime; for magnesium. 4.
Of the two classes of impurities found in water, which is the more
harmful? 5. Name three ways of purifying waters known to be impure, and
tell which is the most effectual.
Experiment No. 49
Testing for Nitrites in Water
To 50 cc. of water in a small beaker add with a pipette 2 cc. of
naphthylamine hydrochloride and then 2 cc. of sulphanilic acid. Stir
well and wait 20 minutes for color to develop. A pink color indicates
nitrites.
REAGENTS USED
Sulphanilic Acid.--Dissolve 5 gm. in 150 cc. of dilute acetic acid;
sp. gr. 1.04.
Naphthylamine Hydrochloride.--Boil 0.1 gm. of solid [Greek:
a]-amidonaphthaline (naphthylamine) in 20 cc. of water, filter the
solution through a plug of absorbent cotton, and mix the nitrate with
180 cc. of dilute acetic acid. All water used must be free from
nitrites, and all vessels must be rinsed out with such water before
tests are applied.
1. Would a water showing the presence of nitrites be a safe drinking
water? Why? 2. What are nitrites? 3. What does the presence of nitrites
indicate? 4. Are small amounts of nitrites, when not associated with
bacteria, injurious?
REVIEW QUESTIONS
CHAPTER I
GENERAL COMPOSITION OF FOODS
1. To what extent is water present in foods? 2. What foods contain the
most, and what foods the least water? 3. How does the water content of
some foods vary with the hydroscopicity of the air? 4. How may changes
in water content of foods affect their weight? 5. Why is it necessary to
consider the water content of foods in assigning nutritive values? 6.
How is the dry matter of a food determined? 7. Why is the determination
of the water in a food often a difficult process? 8. What is the ash or
mineral matter of a food? 9. How is it obtained? 10. What is its source?
11. Of what is the ash of plants composed? 12. What part in plant life
do these ash elements take? 13. Name the ash elements essential for
plant growth. 14. Which of the mineral elements take the most essential
part in animal nutrition? 15. In what form are these elements usually
considered most valuable? 16. Why is sodium chloride or common salt
necessary for animal life? 17. How do food materials differ in ash
content? 18. Define organic matter of foods. 19. How is it obtained? 20.
Of what is it composed? 21. Into what is the organic matter converted
when it is burned? 22. Give the two large classes of organic compounds
found in food materials. 23. Name the various subdivisions of the
non-nitrogenous compounds. 24. What are the carbohydrates? 25. Give
their general composition. 26. What is cellulose? 27. Where is it found?
28. What is its function in plants? 29. What is its food value? 30. In
what way may cellulose be of value in a ration? 31. In what way may it
impart a negative value to a ration? 32. What is starch? 33. Where is
it mainly found in plants? 34. Give the mechanical structure of the
starch grain. 35. Why is starch insoluble in cold water? 36. How do
starch grains from different sources differ in structure? 37. What
effect does heat have upon starch? 38. Define hydration of starch. 39.
Under what conditions does this change take place? 40. What value as a
nutrient does starch possess? 41. What is sugar? 42. How does it
resemble and how differ in composition from starch? 43. What are the
pectose substances? 44. How are they affected by heat? 45. What food
value do they possess? 46. What is nitrogen-free-extract? 47. How is it
obtained? 48. How may the nitrogen-free-extract of one food differ from
that of another? 49. What are the fats? 50. How do they differ in
composition from the starches? 51. Why does fat when burned or digested
produce more heat than starch or sugar? 52. Name the separate fats of
which animal and vegetable foods are composed. 53. Give some of the
physical characteristics of fat. 54. What is the iodine absorption
number of a fat? 55. How does the specific gravity of fat compare with
that of water? 56. Into what two constituents may all fats be separated?
57. What is ether extract? 58. How does the ether extract in fats vary
in composition and nutritive value? 59. What are the organic acids? 60.
Name those most commonly met with in foods. 61. What nutritive value do
they possess? 62. What dietetic value? 63. What value are they to the
growing plant? 64. What organic acids are found in animal foods? 65.
What are the essential oils? 66. How do they differ from the fixed oils,
or fats? 67. What property do the essential oils impart to foods? 68.
What food value do they possess? 69. What dietetic value? 70. What are
the mixed compounds? 71. How may a compound impart a negative value to a
food? 72. What is the nutritive value of the non-nitrogenous compounds,
taken as a class? 73. Why is it necessary that nitrogenous and
non-nitrogenous compounds be blended in a ration? 74. What are the
nitrogenous compounds? 75. How do they differ from the non-nitrogenous
compounds? 76. Name the four subdivisions of the nitrogenous compounds.
77. What is protein? 78. What is characteristic as to its nitrogen
content? 79. What are some of the derivative products that can be
obtained from the protein molecule? 80. How does the protein content of
animal bodies compare with that of plants? 81. Name the various
subdivisions of the proteins. 82. What is albumin, and how may it be
obtained from a food? 83. What is globulin, and how is it obtained from
a food? 84. Give some examples of globulins. 85. What are the
albuminates, and how are they affected by the action of acids and
alkalies? 86. What are the peptones, and how do they differ from the
albumins? 87. How are the peptones produced from other proteids? 88.
What are the insoluble proteids? 89. Give an example. 90. Which of the
proteids are found to the greatest extent in foods? 91. Why may proteids
from different sources vary in their nutritive value? 92. What general
change do the proteids undergo during digestion? 93. What is crude
protein? 94. How is the crude protein content of a food calculated? 95.
Why is the nitrogen content of a food more absolute than the crude
protein content? 96. What food value do the proteins possess? 97. Why
may proteins serve so many functions in the body? 98. Why is protein
necessary as a nutrient? 99. What is the effect of an excess of protein
in the ration? 100. What is the effect of a scant amount of protein in a
ration? 101. What are the albuminoids? 102. Name borne materials that
contain large amounts of albuminoids. 103. What food value do the
albuminoids possess? 104. What are the amids? 105. How are they formed
in plants? 106. What is their source in animals? 107. What general
changes does the element nitrogen undergo in plant and animal bodies?
108. What is the food value of the amids? 109. What are the alkaloids?
110. What is their food value? 111. What effect do some alkaloids exert
upon the animal body? 112. How may they be produced in animal foods?
113. What general relationship exists between the various nitrogenous
compounds? 114. Why is it essential that the animal body be supplied
with nitrogenous food in the form of proteids? 115. Name the cycle of
changes through which the element nitrogen passes in plant and animal
bodies.
CHAPTER II
CHANGES IN COMPOSITION OF FOODS DURING COOKING AND PREPARATION