Journal of Minerals & Materials Characterization & Engineering, Vol. 8, No.5, pp 349-357, 2009
jmmce.org Printed in the USA. All rights reserved
Growth and Characterization Studies of MnHP Single Crystal in Silica Gel
Medium
P. Suresh
2
, G. Kanchana
1
, P. Sundaramoorthi*
2
1
Department of Biochemistry, Muthayammal College of Arts and Science, Rasipuram, Namakkal,
India-637408.
2
Department of Physics, Thiruvalluvar Govt. Arts College, Rasipuram, Namakkal, India-637401.
*Corresponding Author, contact: [e-mail]
Phone: [phone], Fax: [phone]
ABSTRACT
MnHP (Manganese Hydrogen Phosphate) crystals were grown in silica gel medium using
different gel densities, various concentrations of ortho- phosphoric acid and supernatant
solutions in single diffusion process. The gel pH plays an important role in the formation of
different HPO
4
species in the phosphoric system. The pH range in which HPO
42-
ions dominates
were considered which in turn is necessary for the growth of MnHP crystals. The
characterizations of grown crystals were studied by FTIR, SEM, XRD and etching. The results
are reported and discussed in detailed manner.
Key Words: MnHP, calculi, surface morphology, growth parameters, trace element and SMS
gel medium.
1. INTRODUCTION
SHP (Strontium hydrogen phosphate) and BHP (Barium hydrogen phosphate) were grown in
silica gel medium at room temperature and reported [1-2]. In the present investigation, single
crystal of trace element was grown in silica gel medium at different parameters, which contains
one major element (Phosphate), and one minor or trace element (Manganese). MnHP is a single
crystal which typically represents the biological crystals formed in the human urinary tracts
called renal stones. The body of a normal man weighing 70kg contains about 12-20mg
manganese. It is distributed throughout the body tissues and fluids. Bone, kidney, liver, pancreas
and pituitary contain more manganese than other tissues. The manganese

350 P.Suresh, G.Kanchana, P.Sundaramoorthi Vol.8, No.5
content of human blood is very low ranging from 2 to 3 micrograms per 100ml. Only 3-4 per
cent of the manganese present in the regular diet is absorbed and mixed in plasma and the
remaining being excreted in faeces. A normal human body requirement of manganese ranges
from about 2.5 to 5.0 mg per day.
Manganese is present naturally in many foods such as spices, sea foods, cereals, grains and leafy
vegetables. There are some evidences that manganese is essential for the growth of animals,
especially for the normal skeletal growth in the prenatal period. Manganese appears to play an
important role in the functioning of central nervous system. It is also essential for the normal
reproductive function. If the mineral level of the body fluid increases, automatic mineral
deposition starts leading to the development of renal stones. Authors have done a series of
experiments with silica gel crystal growth medium at different pH values ranging from 5.5 to 11.
One can obtain the periodic precipitation, Liesegang rings [3-5] of biological crystals named as
HAP, Brushite, Struvite, BMHP, SMHP etc.
2. MATERIALS AND METHODS
The dissociation of ortho-phosphoric acid system can be represented by three-dissociation
equilibrium and the presence of various ions at various pH values are reported [6]. Based on
these results, the gel pH in the range from 6 to 11 has been used (Milwaukee QS-MN pH-600,
packet digital pH-meter used for measurements) in which the HPO
42-
ion dominates or alone
exists. This decreases the possibility of the occurrence of MnP crystals during MnHP growth.
The crystallization apparatus employed were glass test tubes of 25 mm diameter and 150 mm
long for single diffusion method (SDM). The chemicals used were Excelar-Qualigens(E-Q) AR
grade MnCl
2
and E-Q AR grade ortho-phosphoric acid (Sp.gr.1.75). The SMS gel or water glass
was prepared as per the literature [7]. One of the reactant ortho-phosphoric acid was mixed with
silica gel at desired gel density and elevated temperatures. After the gel set, the supernatant
mixture (Manganese chloride) at a required mole solution was slowly added along the walls of
the growth columns (test tubes) over the set gels and tightly closed to prevent evaporation. Then
the growth systems were allowed to react within the gel medium and the following chemical
reaction take place.
MnCl
2
+ [H
3
PO
4
+ gel]MnHPO
4
+ By- products
2.1. The following observations have been made in the present investigation
The reaction starts immediately after the addition of supernatant solutions. But the nucleation
was observed only after 26 hours and the growth process took a period of nearly one year for
completion. Some well-developed single, poly crystals were observed in the SDM growth
columns. The gel density above 1.06gm/cc and with pH above 8 yielded no crystals, but mean
time reaction takes place. Some of the test tubes of gel density 1.03gm/cc with pH around 6.5

Vol.8, No.5 Growth and Characterization Studies of MnHP Single Crystal in Silica Gel Medium 351
and below 6 were allowed for the reactions to take place. After a period of five months, a less
number of nucleation was observed near the bottom and middle of the test tubes. Some of them
grew as a needle and well transparent single and platelet crystals. From these investigations, the
optimum growth parameters of MnHP crystals were identified and reported in Table-1.
Table-1 MnHP crystal growth parameters in SDM
Gel
density
gm /cc
Ortho-
phosphoric
acid
concentration
in N
Gel+
H
3
PO
4
pH
value
Gel
setting
time in
hrs
Supernatant
concentration
MnCl
2
(M)
Nucleation
observed in
hrs
Growth
period in
days
Types of crystals
observed in all
conditions and
harvested crystal
size
1.04
1
6.4
6.8
6.9
7.3
26
16
1
18
2
-do-
-do-
-do-
26
37
42
99
280
Dendrite crystals
Leaf like crystals
Single,
Poly crystals,
(2mmx 2mm
x2mm)
1.5
6.6
6.9
7.1
8.0
28
1
3
46
-do-
-do-
-do-
-do-
16
26
56
67
290
1.05
1
6.3
6.8
6.9
7.4
34
6
1
68
-do-
-do-
-do-
-do-
22
72
48
88
210
2
6.6
6.9
7.1
7.5
24
1
12
48
-do-
-do-
-do-
-do-
43
30
44
82
275
An extension of the reaction period even up to one and a half year did not improve the size of
these crystals. The growth columns (SDM) of MnHP crystals and harvested MnHP crystal are
shown in Fig-1 and Fig-2 respectively. The maximum dimension of the crystals obtained is 2
mm x 2 mm x 2 mm. In this investigation fast gel set shows non-transparent gel medium and
gives less nucleation and yield.
3. CHARACTERIZATION STUDIES OF MnHP CRYSTALS
3.1. FTIR spectral analysis of MnHP crystal
FTIR spectrometer having KBr pellets sample holder and KBr detector was used for the analysis.
The KBr pellet samples were used and the absorption frequencies range from 600 to 4000 cm
-1
[8-12]. The absorption bonds, absorption frequencies and percentage of transmittance were

352 P.Suresh, G.Kanchana, P.Sundaramoorthi Vol.8, No.5
compared with the reported values. The values are tabulated in Table-2 which confirms the
presence of MnHP crystal constituents.
Fig-1 Fig-2
Fig-1 Growth of MnHP crystals within laboratory environment
Fig-2 Harvested MnHP well transparent crystal
Table-2 FTIR spectral analysis of MnHP Crystal
S.No. Composition/Bond Absorption
frequency
Reported
value
cm-1
Absorption
frequency
Observed
value cm-1
% of
transmittance
1
Manganese & hydrogen
O-H symmetric,
asymmetric (in plane)
3477 to 3207 2811
3559
3497
3310
36
23
19
22
2 O-H out of plane 745 782 47
3 PO
4
group 1000 to 1100 1131
1050
989
12
16
36
4
Manganese/Apatite
group
600-1010
(high
Frequency)
546
587
1086
23
31
14

Vol.8, No.5 Growth and Characterization Studies of MnHP Single Crystal in Silica Gel Medium 353
3.2. Etching study of MnHP crystal
A well-grown MnHP crystal was immersed in HCl solution at a desired concentration. The
dissolution of MnHP crystal depends upon the etchant concentration, temperature, crystal
morphology, etching time etc. [13-16]. The etch pits are shown in Fig-3. The etch pits observed
in the photo are cone pits, leaf pits and step pits.
Fig-3 Etch photo of MnHP crystal at room temperature, HCL as an etchant, etching time - 7
minutes, etchant normality - 2N
3.3. Scanning Electron Microscopic studies of MnHP crystal
A well-grown MnHP single crystal was selected for the investigation of surface morphology by
using SEM. The SEM photograph was made in the version S-300-I instrument. The sample
named VCA-600 kept in lobe middle; the data size was 640x480 µm. The minor and major
magnifications of SEM were about 250 times. SEM acceleration voltage was 25000 volts and the
sample was kept in a high vacuum. 18200µm working distance and monochromatic color mode
was employed. 200µm focusing of MnHP crystal SEM is shown in Fig-4. In the surface analysis
of SEM picture of MnHP crystal, smooth, fine grain boundaries and few valley regions are
observed [17-20].

354 P.Suresh, G.Kanchana, P.Sundaramoorthi Vol.8, No.5
Fig-4 SEM picture of MnHP crystal
3.4. X-ray diffraction of MnHP crystal
The XRD results revealed the crystalline property of crystal. The XRD pattern and diffraction
indices of the MnHP crystals were recorded. Using the programme (Proszki) the lattice
parameters of the MnHP crystal were calculated.
CD0> lo
From to: 1- 25
1H -3. 1. -4. * 10.00 S -3.38 9.10 2.70 **S -2 0.78 2636.5
2H -2. 1. -5. * 10.59 S 12.97 10.73 -1.05 **S -1 0.76 1819.2
3H -4. 1. -3. * 10.17 S -20.14 7.80 6.67 **S 1 0.70 412.8
4H -4. 1. -4. * 11.38 S -12.58 9.53 6.56 **S -1 0.75 1394.4
5H -1. 0. -6. * 11.67 S 25.26 9.19 8.00 **S 1 0.89 4049.4
6H 0. 0. -6. * 11.47 S 35.97 10.46 4.08 **S 2 0.81 3206.0
7H -2. 1. -6. * 12.37 S 16.63 12.09 -0.23 **S 1 0.81 11234.1
8H -4. 2. -4. * 11.91 S -9.79 13.59 -5.82 **S 1 0.80 13123.8
9H -1. 1. -6. * 11.85 S 26.61 13.03 -4.21 **S 1 0.89 1140.9
10H -4. -2. -2. * 9.86 S -43.00 -8.36 54.71 **S 1 0.72 17711.2
11H -1. -3. -4. * 9.94 S 17.37 -9.01 56.58 **S 3 0.74 28197.4
12H -4. -3. -3. * 11.67 S -32.09 -9.59 62.50 **S -2 0.64 1967.7
13H -3. -3. -4. * 11.49 S -11.35 -8.21 58.57 **S 1 0.67 582.6
14H 0. -4. -5. * 12.51 S 34.75 -5.87 53.85 **S -1 0.71 2245.1
15H -4. -2. -4. * 11.90 S -19.11 -3.32 45.32 **S 2 0.68 24786.3
16H -2. -2. -4. * 9.54 S 1.93 -5.39 46.08 **S 1 0.73 15616.1

Vol.8, No.5 Growth and Characterization Studies of MnHP Single Crystal in Silica Gel Medium 355
17H -2. -2. -3. * 8.10 S -7.34 -10.15 55.01 **S -1 0.71 1244.5
18H -3. -2. -2. * 8.25 S -35.75 -12.20 60.50 **S 2 0.72 1817.7
19H -1. 4. -3. * 10.04 S 20.53 28.51 -55.15 **S 2 0.87 8445.4
20H -2. 4. -2. * 9.76 S -2.02 27.31 -51.90 **S 1 1.04 21079.8
21H -3. 5. 1. * 11.90 S -43.69 29.79 -53.96 **S 1 1.00 8956.4
22H -3. 5. -1. * 11.90 S -20.12 29.20 -52.26 **S 1 1.15 8967.8
23H -2. 5. -3. * 12.25 S 7.61 30.13 -53.93 **S 1 1.01 21325.2
24H -2. 5. -2. * 11.47 S -0.90 31.81 -59.61 **S 1 1.19 694.0
25H -1. 4. -1. * 8.45 S 0.84 33.78 -73.19 **S 1 1.13 22465.5
CD0> reind
Nr S H K L Dev-Ang dTh dPh dCh 0.0093594
1 H -2.999 1.007 -4.003 0.0757 -0.006 -0.013 0.073 0.0007065
2 H -1.999 1.001 -5.002 0.0211 -0.002 -0.012 0.017 0.0002248
3 H -4.000 0.993 -3.001 0.0819 0.003 -0.020 -0.078 0.0007233
4 H -4.000 1.000 -4.001 0.0109 -0.002 -0.011 -0.008 0.0001326
5 H -0.999 -0.003 -5.999 0.0329 0.003 -0.018 -0.029 0.0003606
6 H 0.001 -0.005 -5.990 0.0476 0.019 -0.020 -0.042 0.0010464
7 H -2.000 0.998 -6.001 0.0226 -0.001 -0.008 -0.0221 0.0002412
8 H -4.002 2.009 -4.002 0.0764 -0.012 0.012 0.076 0.0009725
9 H -1.000 1.001 -6.002 0.0124 -0.005 -0.005 0.012 0.0002521
10 H -3.998 -2.004 -2.001 0.0486 0.000 -0.029 -0.045 0.0004099
11 H -1.000 -2.992 -4.006 0.1106 0.000 0.037 0.108 0.0009394
12 H -4.001 -2.997 -3.003 0.0351 -0.001 -0.011 0.033 0.0003537
13 H -2.994 -2.998 -3.990 0.0425 0.020 0.001 -0.041 0.0010662
14 H -0.003 -3.997 -5.005 0.0578 -0.002 0.063 0.033 0.0006273
15 H -4.000 -2.000 -3.998 0.0161 0.003 0.014 -0.012 0.0002309
16 H -2.001 -2.002 -3.996 0.0523 0.004 0.020 -0.055 0.0004614
17 H -2.005 -2.007 -3.002 0.0712 -0.015 0.039 -0.068 0.0008623
18 H -3.002 -2.005 -2.001 0.0525 -0.009 -0.002 -0.053 0.0005692
19 H -1.004 3.991 -3.005 0.1136 0.007 -0.024 -0.112 0.0010373
20 H -1.999 4.003 -2.000 0.0272 -0.005 -0.002 0.028 0.0003260
21 H -3.003 4.999 1.003 0.0405 -0.002 0.034 -0.032 0.0004221
22 H -3.000 5.001 -0.999 0.0141 0.000 0.016 0.008 0.0001445
23 H -1.999 5.003 -3.001 0.0257 -0.005 -0.010 0.024 0.0003557
24 H -1.998 5.001 -1.999 0.0216 0.000 0.003 0.021 0.0002118
25 H -1.000 3.999 -1.000 0.0046 0.002 -0.007 -0.002 0.0000976
Reciprocal axis matrix Direct axis matrix
-0.076371 0.020678 0.056979 -7.659393 -5.683682 -3.047902
-0.056719 0.022058 -0.074083 2.150182 2.314291 -9.716051
-0.030412 -0.093093 -0.005038 6.504328 -8.458021 -0.559365

356 P.Suresh, G.Kanchana, P.Sundaramoorthi Vol.8, No.5
Niggli-values Sigma direct axis matrix
100.2603 104.3808 114.1574 0.002766 0.001097 0.001836
-0.1541 -0.0417 -0.0091 0.005859 0.002324 0.003892
0.004838 0.001919 0.003213
Cell parameters Sigma cell parameters
10.20230 10.2067 10.5844 0.0022 0.0038 0.0034
90.2008 90.0243 90.1752 0.0286 0.0238 0.0291
-0.0014141 -0.000388 -0.000099 0.000499 0.000417 0.000509
Volume= 1102.1727 0.5956
Index-Status: HHHHHHHHHHHHHHHHHHHHHHHHH
CD0>
The lattice parameters are a=10.02Å, b=10.20Å, c=10.58Å, α=90.2˚, β= 90.0˚ and γ=90.1˚. The
volume of the unit cell of the MnHP crystal is 1102.1727 (Å)
3
. From the above data it was
confirmed that MnHP crystal system is triclinic [21-22].
4. CONCLUSION
The MnHP crystals were grown at room temperature and found optimum growth parameters.
MnHP crystal growth columns and harvested crystal are photographed. FTIR-spectrum recorded
the functional group frequencies of MnHP grown crystal constituents. These results were
recorded and compared with the reported values. Chemical etching was done at room
temperature, which revealed the grown crystal defects. SEM analysis was also done and it
revealed the surface morphology of MnHP crystal. MnHP lattice parameters were calculated by
XRD.
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Vol.8, No.5 Growth and Characterization Studies of MnHP Single Crystal in Silica Gel Medium 357
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