May,
1911
T H E JOCRA\-,-lL OF I.VDCSTRIAL -A-\lD E.\-GIiYEERIA\7G
cent. aqueous solution of hydroxylamine hydrochloride, then treated, with thorough agitation, with about 4 cc. of sodium hypochlorite solution. In the presence of acetone, the ether layer shows a blue or bluish green tint. Excess of hypochlorite sol.Jtion should be avoided, but the amount of hydroxylamine hydrochloride solution used is immaterial. In the Pliarvzacopoca iVedcrlatzdica,l an interesting test for the detection of acetone is given. T w o cc. of the ether are mixed with 6 drops of mercuric chloride solution and 6 cc. of barium hydroxide solution; the clear filtrate is then tested with ammonium sulphide solution, whereby, the presence of the compound 2 C,H 3 HgO is made evident. Other method:; for the detection of acetone could be applied in the case of ether, but it is unnecessary t o look for such an improbable contaminant a t the present time. Acetaldehyde is the only substance other than alcohol which will likely respond to the iodoform test when it is applied to anaesthetic ether. ( T o be c o n t i n u e d . )
THE ACTION OF ALKALI SALTS UPON PORTLAND CEMENT. B y E D M U N D BURKEAND REUBEN11, P I N C K S E Y .
Keceived February 10, 1911.
I n recent years damage to cement wcrk placed in alkali water has been frequently reported. A usual feature of such damage is t h a t the cement bulges, cracks, and finally crumbles completely. I n some cases where the damage has continued. to what may be considered its conclusion, the cement has been described as having the appearance and consistency of fresh lime mortar. I n every case of which we have reports, the damage can be explained b y considering it to be due to internal expansion within the cement mass, which breaks the hold of the cement particles upon one another. Such damage has been reported from nearly all of the western states, and investigations to discover the cause have been undertaken by the experiment stations of a t least three of these states. The investigation here reported occupied about two years’ time and was undertaken for the purpose or^ learning, if possible: I . Whether the destructive action is really due to “ alkali.” 2 . If so; to which one or what ones of the salts that make up “alkali.” 3 . To suggest some means whereby the damage may be avoided or lessened. Examinations$ by one of us had shown quite conclusively t h a t in a certain case of damage to a cement sewer, the points of greatest damage ‘coincided with the point where the soil contained the greatest amount of alkali. In any discussion of the effect of alkali, the first step is obviously to determine what is meant by the term. 11905, p. 2 T . See Bzdietin 69 of the Montana Experiment Station.
2
CHEIIISTRY. X L KA L I
317
.
“Alkali,” in the popular sense, is a term used to designate the soluble salts t h a t accumulate in regions of little rainfall. Such salts are formed by the decay of rocks and are present in all soils as formed, but with sufficient rainfall and drainage are leached out and removed in the drainage water. They accumulate wherever such alkali-laden waters collect and evaporate, as in the ocean, salt lakes, or soils which receive such drain waters and allow them to evaporate. These accumulations, in the form of more or less concentrated solutions, or as dry salts, may amount to only a few pounds per acre, or in some places become great salt deposits of inches or feet in thickness. S.4LTS IS A L K A L I .
The salts usually present in greatest amounts in the soils and drain waters of the West are the sulphates, carbonates and chlorides of sodium, magnesium, and, in a smaller amount, of calcium. The sodium sulphate (which when crystallized with water is sometimes called Glauber’s salt) makes up the larger part of the deposits generally known as “white alkali;” usually also there is more or less of the magnesium sulphate (which is also known as Epsom salts). The so-called “black alkali” is largely sodium carbonate. I t is called “black” from its property of dissolving organic matter from the soil, forming dark-colored solutions. This property is not shared b y the sulphates, though they are usually present with the sodium carbonate in black alkali. As all these salts are very soluble, they are deposited in solid form only when the drain waters are very much concentrated by evaporation, but they are present in the drain waters of all alkali soils, the white alkali salts being most abundant. A S A L Y S E S O F ALK.\LI.
Following are given some analyses of the alkali found in soil a t different points where damage to cement work has been reported:
4543 304 343 3i2 392 405
0.110 0.121 1.750 0 550 0 254 0.292
4.840 2.867 5 470 20.625 12.005 11.546
23 830 33.398 2.190 17.875 25 387 26 858
0 540 1 859 2 190 1.237 1.181 1,500
59,670 59.696 54.700 44.000 56.875 53.799
0 000 0.000 0.000 2.475 0.000 0.761
5.860 1.426 12.690 0.000 2.283 04.820
3.130 0.323 21.000 13 200 1.889 0.401
NoTE.-These analyses, except No. 4 j 4 3 , were made b y Dr. F. ST‘. Traphagen and published in Bulletin 18 of the Montana Experiment Station. In order to determine which of the alkali salts was responsible for the damage to cement work, it was determined to test the effect of the salts separately upon the cement, using first the ones most abundant. P R E L I M I i i A K Y TESTS ,
A quantity of cement which had been “ s e t ” with water and allowed to harden a few weeks was ground
a
T H E JOURh’AL OF I N D U S T R I A L A N D ENGINEERI:\‘G to pass a sieve of one hundred meshes per linear inch. This cement was placed on a filter paper in a Buchner funnel and a staurated solution of sodium sulphate allowed t o percolate through it. The filtrate, after passing through the cement, was then examined for any substance t h a t might have been dissolved from the cement. Very small amounts were found, entirely too little t o account for the damage, so that no light was thrown upon the problem until it was noted t h a t the filtrate was intensely alkaline. Further tests showed this to be due to sodium hydroxide. I n order t o test the matter quantitatively, jo grams each of a number of different set cements were treated with the sodium sulphate solution, using a I O per cent. solution to avoid the variation of strength with changes of temperature that had been observed when the saturated solution was employed. Although a number of different cements were subjected to each treatment reported in this paper, the results were very similar, and hence only a single cement is shown in the analysis. The cement selected for the report is a Portland of good reputation, and is believed to be representative of the best cements upon the market. Each half liter of the solution filtered through the cement was taken separately and tested by titration for the amount of alkalinity in the filtrate, and the amounts of lime, sulphates, silica, and alumina determined gravimetrically. After two or three liters of the solution had passed through the cement (in about five weeks’ time), the cement had a bulged and cracked appearance, similar to that noted in the destruction of cement by natural alkali. TABLEI --ANALYSIS
OF
FILTRATE SECURED BY LEACHING 5 0 GRAIIS SET
C E M E N T WITH
10
FER CENT
NalSOa
Amount of N/10 acid required t o neutralize. cc.
Lime, CaO. 0 3900 0.3800 0.3340 0.2480
560 1st 500 c c . . . . . . . . . . . . . . 326 2nd 500 c c . . . . . . . . . . . . . 3rd 500 c c . , . . . . . . . . . . . . 262 4th 500 c c . . . . . . . . . . . . . . 194 5th 500 c c . , . . . . . . . . . . . . . . . .
-
Total.. . . . . . . . . . . . . . . . . 1342
SOLUTION
......
Sulphuric anhydride,
so3.
.......
~
1.3520
Present in orignal solution 1.3520 gain
104.2800 112.6831 8.4031 loss
The amount of sodium hydroxide (as shown by the total alkalinity) was high in the first half liter, and rapidly diminished in successive portions, with a corresponding increase of sulphates , in the same portions. From this i t was evident that a reaction was taking place between the sodium sulphate and some hydroxide present in the set cement. This evidence led us to a consideration of the compounds present in cement, and of the theories that have been propounded in regard to the setting of cement.
-
Setting of Cement. COMPOUNDS P R E S E N T .
So far as we could learn, all investigators agree t h a t in the setting of cement a greater or less amount of calcium hydroxide is formed, which is present in
May, 1911
a crystalline form in the set cement. Le Chatelier states, and others agree, notably the Newberrys and Clifford Richardson, t h a t the important compounds present in cement clinker are tricalcium-silicate (Si0,.3CaO), and tricalcium-aluminate (A1,03.3CaO), and Richardson adds “ t h a t if only these compounds are present, and in the proportion of six molecules of the silicate to one of the aluminate, the clinker is a pure ‘Alit,”’ which Tournbohm, a Swedish investigator, has identified as the preponderating mineral constituent of typical cement clinker. Le Chatelier also states, and Richardson agrees, that upon coming in contact with water the tricalcium-silicate reacts t o form a lower hydrated silicate and sets free two molecules of calcium hydroxide, gH,O = z(SiO,.gCaO) (CaO.SiO,) ,.5 H,O 4Ca (OH)2,
+
+
while the tricalcium aluminate reacts with water and a portion of the calcium hydroxide, forming a lower hydrated aluminate, Ca,A1,0, Ca(OH), I I H , O = Ca,A1,0,.12H,0.
+
+
Richardson states that “The strength of Portland cement after setting is due entirely to crystallized calcium hydrate which binds together the particles of undecomposed cement.” Calculations from these reactions show that if cement had the ideal composition assumed by Richardson the percentages in the unset cement would be: lime (CaO) 7 1 . 7 per cent., silica (SiO,) 2 2 per cent., alumina (A1,0,) 6 . 2 per cent., which altogether would require for its complete hydration according to the reactions given above 4 1 . 7 per cent. of its weight of water; or, in the set cement of t h a t composition, the percentages would be: lime 50.7 per cent., silica 1 5 . 6 per cent., alumina 4.4 per cent., water 2 9 . 5 per cent. Thus 3 7 . 5 per cent. of the weight of the set cement would be calcium hydroxide, Ca(OH),. Comparison of the percentages given above with numerous analyses of Portland cement show that commercial cement must contain a large proportion of other constituents of lower lime content than the tricalcium silicate and aluminate, and these lower lime compounds may or may not “hydrate,” or take up water when given the opportunity. We do not know how completely the reactions given by Le Chatelier take place, nor the time requred before the maximum hydration is accomplished. I t seems tolerably well agreed that the reaction involving the aluminate is more ra’pid a t first than that involving the silicate, that is, “The aluminates are responsible for the set, the silicates for the subsequent slower hardennig.” This would, of course, indicate that the silicate continues to take up water for a considerable period. In fact, practical cement workers have long recognized that it is necessary to keep the cement wet for days or weeks while the hardening is taking place. Richardson’s statement that calcium hydroxide is the binding material of set cement seems to be correct; but, whether so or not, this substance certainly ~
24,0300 23 ,4000 28.4000 28.4500
CHEMISTRY.
I ”
May, 1911
T H E JOC-RSAL OF I.I-DL-STRl.4L A S D E-l."GIAVEERIIZ'G C H E M I S T R Y .
occupies space in the set cement, and seems to be the only, or, a t least, the principal substance in the cement that reacts x i t h the alkali salts (except the sodium carbonate, whose reaction will be discussed later). GI'PSCLZ F O R h I l 3 D B Y .\CTION O F S O D I U X S U L P H A T E .
Since the onl;,. reaction of which we had any evidence mas the interchange between the calcium hydroxide of the cement and the sodium sulphate applied in the :solution, forming soluble sodium hydroxide, C a ( O H ) , + N + S 0 4 i?€€,@ = CaS04.2H,0 + 2 N a ( O H ) , \\-e came t o the belief that a molecularly equivalent amount of calcium sulphate must be formed, which, because of its relative insolubility must remain in the space formerly occupied by the calcium hydroxide. Since 1T.e know that calcium sulphate in the presence of water takes the form of gypsum (CaSO,.z€I,O), and that this substance is much used as a cement (plaster of Paris), we were unable to see how the reaction could be so destructive as observation has shox-n i t to be, until we began to consider the relative space that would be occupied by molecular equivalents of calcium hydroxide and gypsum, or even anhydrite, the Ti-aterfree calcium sulphate. The molecular weights are : calcium hydroxide Ca(OH)?,71;calcium sulphate (anhydrite) CaSO,, 1 3 6 ; gypsum, CaSO, zH,O, 1 7 2 . The specific gravities are: calcium hydroxide, 2 , 0 7 8 ; calcium sulphate (anhydrite), 2 . 9 j to 2 . 9 8 ; gypsum, CaSO,. zH,O, 2.32. Then, dividing the molecular weight in grams by the specific gravity, we find the space occupied I
_
bj- 7 4 grams of calcium hydroxide to be
or
74
2.078'
3 5 . 6 cc. The space occupied by 136 grams (a molecularly equivalent amount) of anhydrite is
'-36 or 2.98
45.7
cc.
grams of gypsum is
T h e ' space occupied 17'
2.32
by
172
, or 7 4 . 1 cc.
These quantities, then, occupy space in the ratios of 3 5 . 6 cc., 4 5 . 7 cc., and 74. I cc., or I .o, I . 28, 2 . 0 8 . Or, to state the same facts in tabular form: Calcium hydroxide. &(OH)? The molecular weights a r e . . . . . . . . . . . . . . . 74 0 The specific gravities are 2 .Oi8 Therefore t h e space occupied i s . . . . . . . . . . . . . . .
74 -2 078
XThich i s . , . . . . . . . . . . . . 35 . 6 1,O Or in the r a t i o . . . . . . . . .
Anhydrite, CaS04.
Gypsum. CaS04.2H20
136 2.95 t o 2 98
172 0 2.32
136 ~~~
2.98 45.7 1.28
172
.~ -
2.32 74.1 2.08
As anhydrite takes up water to form gypsum, the greater ratio, I : 2 . 0 8 , is the final one t o be taken into consideration. This calcium sulphate will certainly act t o some extent as a binder; nevertheless, when the calcium hydroxide is replaced by a substance requiring 2 . 0 8 times as much space, that substance must exert a disrupting influence, like that observed as the effect of alkali. This expansion, due to an increased amount
319
of material, is the most important point to be considered in this investigation. C03IPOUiYDS R E S U L T I N G F R O M
O T H E R .4LKALI S A L T S .
In considering what would be the probable effect of the different salt solutions, we then assumed that if sodium carbonate should be substituted for the sulphate and allowed to act upon the set cement, the resulting compounds would be sodium hydroxide in solution, as in the first case: and calcium carbonate remaining in the space formerly occupied by the calcium hydroxide. This compound will also have some value as a binder, but will likewise exert the same sort of disrupting force, though not in the same degree, as the gypsum. -1ssurning that the reaction takes place, Ca(OH), + Na,CO, = CaCO, zNaOH, the molecular equivalents have the weights :
+
Calcium hydroxide. Ca(OI1)2. 'The nio!eciilar weights arc- . . . . . .;'he spec;lic prai-ities a r e . . . . . .
7 1 .0 2 078
T h e space occupied will b e . . . . . . .
74 ~-
Calcium carbonate, CaC03. 100
2.72 100
2 078 Or . . . . . . . . . . . . . . . . . . . 35 6 'The ratio is . . . . . . . . . . . . . . . . . . . 1 0
2.72 36.8 1.03
The action of magnesium sulphate, which occurs in abundance in alkali, will be highly destructive, because both of the compounds resulting from the reaction, magnesium hydroxide, MgSO, Ca(OH), 2H,O = CaS04.2H,0 blg(OH),, and gypsum, are but slightly soluble, hence they will both remain in the position formerly occupied by the calcium hJ-droxide:
+
+
+
Anhydrite magnesium hydroxide, CaSOl 3Ig(OH)z.
+
Calcium hydroxide. C a ( 0 H 12. The relative molecular weights a r e , . , , , , , , , , . 7 4 . 0 136.0 T h e specific gravities a r e , 2 . 0 7 8 2.94
+
'fherefore the relative space occupied is, ,
58 + _.
Which i s . . . . . . . . . . . . . . . . Or . . . . . . . . . . . . . . . . . . . .
i4 ..~ ~-
2.078 35.6 1.0
136 2.94 71.1
1.98
+
+ 58.0 2.34
2.34
Gypsum imagnesium hydroxide, C a S 0 4 . H 2 0iMg(OH)~. 172.0 2 32
+ 58.0 + 2.34
172 2.32
58 +
2:34
99.0 2.78
Therefore the relative space' occupied will be : 2.078 2.34 2.32 2 . 3 4 which is 356 : 7 1 1 or 356 : 990 I : 1 . 9 8 or I : 2 . 7 8 The ratio I : 2 . 7 8 is the one more probable, as the calcium sulphate tends to take the form of gypsum. With this ratio before us, it is easy t o see why numerous investigators have considered from practical tests that the magnesium salts in sea water are the ones responsible for the damage observed in certain instances. Some of these investigators have held, that in such cases, new compounds were formed which crystallized, and in the crystallization exerted a pressure that disrupted the cement; t h a t is, they considered
320
THE J O C R N A L OF I L T D C S T R I A L A N D E.YGIXEERIA\7G C H E M I S T R Y . ’
the physical state of the reaction product to be the controlling factor, rather than considering the amount of material present. I t seems clear, however, t h a t t h e amount of material concerned in the reaction can be determined with a fair degree of accuracy, and t h a t the increase in material present sufficiently accounts for the increase in space required, so t h a t the destructive internal strains are explained without resorting t o the crystallization theory. h THEORY O F DISINTEGRilTION,
h working theory, then, may be formulated thus: The chemical reaction of alkali that is destructive t o cement work is a double decomposition between the various alkali salts and calcium hydroxide, which is a n unavoidable constituent, and probably the binding constituent, of all set cement whether the cement is classed as “Portland,” “natural,” or “slag.” This reaction removes a greater or less amount of the calcium hydroxide, the amount depending upon the salts present, the concentration of the solution, the rate of percolation and imperviousness of the cement, and the solubility of the reaction products, and deposits in its place, in most cases, a molecularly equivalent amount of other compounds, which have in some cases cementing properties, but occupy more space than the calcium hydroxide. This incyease o j space occupied disrupts the cement, causing it to bulge, crack, and crumble. TESTS W I T H VARIOUS SALTS.
I n order t o test this theory we took the cement, set and ground as previously described, placed twenty-five or fifty grams on the Buchner funnel, and added the solution as follows: One-half liter of the Solution was placed in a glass-stoppered bottle and poured, a few cc. a t a time, upon the cements, a n d allowed to pass through, using reduced pressure from the filter pump as it becomes necessary, but avoiding it as much as possible in order to avoid :loss of water by evaporation from the filtrate. When the half liter had been used the filtrate was returned t o the bottle and a fresh supply of the alkali solution provided. Each half liter of the filtrate was thus kept separately and tested separately in order t o learn how rapidly the action was proceeding and when i t ceased. A number of different cements were treated in this manner, of which the one selected €or complete analysis is believed t o be in every way representative. The samples of cement were obtained directly from the manufacturers, who wer5 informed of the object of the investigation and donated the samples. As they knew the tests would be severe, they undoubtedly provided us with the best cement they were able t o manufacture. T H E SALTS USED.
From the first we took care t o include samples of the three classes of cements, Portland, slag, and natural. Each cement was treated with the follow.ing solutions :
May, 1911
( I ) Distilled water, using both 5 0 grams and 2 5 grams. Five weeks. This test mas made a t the same time and on funnels standing beside those with the sodium sulphate. ( 2 ) I O per cent. sodium sulphate, Na,SO,. This also was tested twice, once using 5 0 g. of the set cement for each sample, once using 2 j grams. Tests continued about five weeks. (3) 2 p e i cent. magnesium sulphate, LIgSO,. Eight weeks. 2 j-gram samples only. (4) 2 per cent. sodium carbonate, Na,CO,. Eight weeks. 25-gram samples only, (j) Sea water. 3 . j per cent. total salts. Eleven weeks. 25-gram samples only. The funnels mere covered with watch glasses to reduce evaporation and to protect the samples from dust, and, except in the case of the first sodium sulphate treatment, the funnels were lightly coated above the sample with vaseline, in order t o prevent loss of the salts b y creeping over the top. N o special attempt was made to protect the cement from contact with the air, and, in fact, in most cakes there was an increase in the amount of carbon dioxide present in the sample. There was certainly some loss of water by evaporation, and probably some quantity of soluble salts was retained in the sample, so that the quantitative analyses of the filtrates do not exactly indicate the quantitative changes t h a t have taken place in the solutions. The samples, after treatment with the solutions, were in some cases washed on the funnel with distilled water and the washings analyzed. The cements, when the salt solutions were added, hardened or “ s e t ” in a manner similar to fresh cement when it is treated with water, though the mass did not set so hard after being ground, as fresh cement does. The solution a t first percolated rapidly but after a few days the percolation diminished, and in some cases almost entirely ceased, even when the filter pump was used. This slackening occurred before any noticeable bulging or cracking, and in a number of cases, after the disintegration became marked, the rate of percolation again increased. After the samples had been treated with the salt solutions, they were dried to a more or less nearly air-dry condition, ground and thoroughly mixed, first being freed as completely as might be from the adhering filter paper. An analysis was made of the residue from each treatment. An analysis was also made of the set cement as i t was taken for treatment. The filtrate was analyzed as soon as the half-liter portions had been secured. 2 j cc. from each were titrated with IO sulphuric acid for total alkalinity; 5 , 2 5 , or 5 0 cc. were taken for gravimetric determination of sulphates (calculated t o SO,); the same for lime (CaO), and usually roo cc. for silica (SiO,). I n case there was reason to suppose that there was magnesium present in the filtrate, a suitable amount was taken for its determination. The titration with acid shows approximately the total amount of calcium hydroxide which has reacted
May,
T H E JOC'R,VAL OF I.\-DC7STRIA4L ,4A'D ESGI!\'EERI,"\G
191 I
OF
CElIEh-TS
WITH
T A B L E III.--.kNALYSIS
DISTILLED\ v A T E R ,
Moisture. . . . . . . . . . . . . . . . . . . CO?.. . . . . . . . . . . . . . . . . . . Combined water. . . . . . . . . . . Loss on ignition.. . . . . . . . . . Silica ( S O ? ). . . . . . . . . . . . . . Iron oxide (FenOs) Aluminum lOCNT
Potnssiuni bromide ( K B r . . . . . . . . . 3 96 Grams Sodium chloride (SaCIl. . . . . . . . . . 1100.00 .. Potassium sulphate (KrSO1,. . . . . . . . . . 35 00 Calcium sulphate ,:CaSO,! . . . . . . . . . . 57.12 Magnesium sulphate (UgSO,l . . . . . . 57 .84 .. Magnesium chloride (MgCI1). . . . . . . 151 85 .. Magnesium carbonate (MgCO:41,. . . . . . . . . 4.22 " Distilled w a t e r . . . . . . . . . . . . . . . . . . 40 0 Liters
OF F I L T R A T E SECURED CEMENT KITH SEA \X-ATER
OF M A T E R I A L IX
1.0006
RESIXICE SECURED
BY
LEACHING
2 3 GR.43lS CEMENT JTITH SEA \vATER.
Grams Silica in cement before treatment (19 80 per cent. I . . . . . . . . . . . . 4 . 9 5 0 0 \\-eight of cement a f t e r treatment (silica = 1 6 . 4 9 per c e n t . ) . . . . 30.0182 Original weight of c e m e n t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 0000 Increase in w e i g h t . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.0182
Dry weight before t r e a t m e n t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.13i.5 Dry weight after treatment (ivater = 8 . 2 5 per c e n t . ) ,. . . . . . . . . . 24,5417 Increase in dry weight.
...............................
Ignited weight before treatment (loss = 1 6 . 6 0 per c e n t . ) , . . . . . Ignited weight after treatment (loss = 28 60 per cent ) . . , , . . , , Increase in ignited weight..
..........................
Before.
After.
Loss.
Calcium oxide (CaO). . . . . . 12.4155 9 6058 2.8117 Sulphuric anhydride (SO31 0.3875 1.2908 .... Magnesium oxide ( I f g o ) .. . 0.3250 2 . i o 1 6 .... Potassium oxide (K2O) . . . 0 . 2 i 7 5 0,2341 0,0434 Sodium oxide ( S a ? O )
)
3.4042 20 8500 21.4330 0 5830
Gain.
.... 0 9033 2 3766
-~ .__
2 8551
S e t gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 2799 2 8551 0.4248
0 4248
n
16x2
The residue, on the other hand, has increased in magnesia and in sulphates, and has lost lime. The ratios among these substances are such as to indicate that not all the change is due to interaction between the calcium hydroxide and magnesium sulphate, but some of the magnesium chloride in the sea water must have taken part in the reaction as well. In this treatment with sea water, we have a solution that is essentially similar to the natural alkali
-
~
T H E J O U R A J A L OF I N D U S T R I A L A N D EATGINEERIlVG C H E M I S T R Y .
326
solutions that occur in the western states. Its action upon cement is such as would bring about the effects t h a t have been noted a t numerous points in the West, as well as those noted in some instances where wharves breakwaters, etc., have been destroyed by the action of sea water. The commonly held opinion that the magnesium sulphate in the sea w%ter is most. active in causing this destruction is confirmed b y our data on the treatment with the single salts, which show that both magnesium ions and sulphate ions are capable of causing such disruption. R E C.4P I T U L A TI0N . When set cement is leached with solutions of certain salts, the salts react with the calcium hvdroxide of the cement, forming the corresponding hydroxides and calcium salts. I n the cases of the salts studied, sodium sulphate, sodium carbonate, magnesium sulphate, the calcium salts formed are insoluble, and therefore remain in the cement where they are formed. This is also the case with the magnesium hydroxide formed, but not with the sodium hydroxide, which is soluble, and therefore remains in the solution obtained as a filtrate. The solid matter remaining in the cement is greater in weight and in space required than the calcium hydroxide which it displaces. The increased space necessary is only obtained by forcing apart the cement particles, thus breaking their hold upon each other, and cracking or weakening the cement. The action of the sea water, a mixture of salts in solution, is such as would be expected from the action of the separate salts studied. LABORATORY OF
THE
AGRICULTURAL
EXPERIMENT STATION. BOZEMAN. MONTANA.
purifier would a t least be needed; a chemical softening plant would be better. Saline waters, third group (Table 11), are so called because of a preponderance of the chlorides of the alkalies and alkaline earths. As nearly all of our waters contain chlorides the minimum amount of such compounds necessary to place a water in this class is arbitrarily fixed a t 170 parts per million or about I O grains per U. S. gallon. Unless the chlorides are present in considerable quantity they are not difficult t o handle in boilers. TABLEI.-BOILER TVATEKPURIFICATION. Synopsis. to the quality of water. 2 . Scaling-Corrosion, priming, foaming. 3. Mechanical Filtration. 1. Clear water basin: bars. , 2. Screens. 3 . Settling tanks in duplicate. (Sand. 4 . Filters] Coke. ( Wood. H o t well. Open heater. 1. Geiteval-Relating
Closed heater, pressure. 4 . Tizern~al.
B O I L E R WATERS.
For convenience I have classified boiler water purifiers according t o Table I and types of water according to Table 11. Waters of the first group (Table 11) are exceptionally soft and, unless all of the hardness is due to sulphate of lime, can be used in the plant with thermal treatment only. The precipitated carbonates and organic matter are blown out of the boiler a t intervals. Waters of the second group (Table 11) can be used in boilers only under exceptional conditions without the use of some apparatus or chemical to disorganize their scaling properties. If the entire hardness were due t o sulphates a live steam heater or chemical
{ b tubes’ drips. a
Live steam heater. External sand filters. Economizers. Fire box heater. Mud drum. Internal heater. Skimmer, dome-funnel.
5 . Thermo-Physical. Internal boiler purgers. coal d u s t , sawdust. kerosene, starch. 6 . Tizermo-Chemical. soda. (a) Harrison. ( b ) Bonnell Electro-Chenzical, zinc-balls, aluminum. 8 Chemical-Internal, boiler compounds. 9. Chemical-External, (a) Intermittent. ( b ) Continuous ( c ) Intermittent and continuous. 10. Spec& Iiistaitces. TABLE II.-BOILER
B y WM. M. BOOTH,Chemical Engineer, Syracuse, N. Y.
External
Internal
BOILER WATER PURIFICATION.
The purpose of this paper is to sketch the development of boiler water purification from a purely thermal process to a highly organized chemical system and in addition t o give a n idea of conditions actually met in various plants. To aid us in this discussion I have made use of tabulations which will be referred to as Tables I , 11, I11 and IV.
May, 191 I
JvATERS CLASSIFIED !lCCORDING TO QUANTITYOF SCALE-FORMING SOLIDS.
Soft-To 50 parts per million. (a) Rain or snow. ( b ) Water from granite or quartz rock regions. ( c ) Returned water. ( d ) Sulamps. (e) Lakes. (f) Large rivers. Hard-Above 8 5 parts per million. ( a ) Springs. ( b ) Lakes. ( c ) Small rivers and creeks. ( d ) Wells. Saline-Containing above 17d parts per million chlorides, of Ca, Mg; Nm or K . ( a ) Sea. ( b ) Wells. ( c ) Mineral springs. Alkaline-Carbonates or bicarbonates of the-alkalies. (a) Western plains. ( b ) Springs. Acid-Containing
any strongIminerallacid.
TABLE III.-BoILER
WATER
TREATMENT.
To 5 0 Parts per Million-Thermal. From 50-170 Parts per Million: 1. Heaters. 2. Lime. 3. Soda, hot or cold. 4. Caustic soda. 5 . Phosphate of soda.
